Profiling key excipients in commercial oral antibiotic suspensions: a descriptive study of formulation trends and selected safety concerns

Profiling key excipients in commercial oral antibiotic suspensions: a descriptive study of formulation trends and selected safety concerns Twana Mohammed M. Ways1 1 Department of Pharmaceutics, College of Pharmacy, University of Sulaimani, Sulaymaniyah, 46001, Kurdistan Region, Iraq Corresponding author: Twana Mohammed M. Ways (twa[email protected]u.iq) Received 6 July 2025♦ Accepted 17 September 2025♦ Published 9 October 2025 Citation: M. Ways TM (2025) Profiling key excipients in commercial oral antibiotic suspensions: a descriptive study of formulation trends and selected safety concerns. Pharmacia 72: 1–10. https://doi.org/10.3897/pharmacia.72.e164270 Abstract There is limited descriptive data on excipient use in oral antibiotic suspensions; this study provides a novel evaluation of commonly used excipients and their formulation rationale. A total of 41 suspensions representing nine antibiotic types were analyzed using patient information leaflets. The frequency of each excipient class was determined, and associations between suspending agents or preservatives and antibiotic classes were assessed. Selected qualitative safety concerns related to the listed excipients were identified. Amoxicillin/clavulanate was the most frequently represented antibiotic. Excipient details were available in 31 products, while 10 lacked disclosure. Xanthan gum, sodium benzoate, sucrose, titanium dioxide, and strawberry flavor were the most commonly used suspending agent, preservative, sweetener, colorant, and flavoring agent, respectively. Combinations of suspending agents, particularly xanthan gum with colloidal silicon dioxide, were common, whereas preservative combinations were rare. A significant association was observed between the type of suspending agent and the antibiotic class (p < 0.001), as well as between preservative type and antibiotic class (p = 0.001). The findings highlight formulation patterns, safety concerns, and transparency issues, providing novel insights to support safer pharmaceutical products and guide regulatory practice. Keywords excipients, pediatric formulations, preservatives, safety concerns, suspending agents, suspensions, sweeteners Introduction Oral suspensions are commonly used to deliver drugs that are insoluble or unstable in solution. Antibiotics are often formulated as oral suspensions because many are unstable in aqueous solution but remain stable in dry powder form until reconstitution. This strategy extends the shelf life and improves the therapeutic efficacy of the products. Oral suspensions also play a vital role in the effective delivery of antibiotics because of their suitability for pediatric, geriatric, and other patients with difficulty swallowing tablets and capsules (Fox 2014). Suspensions have improved flexibility in dosing, which allows easy adjustment of doses by changing the volume administered (using calibrated dosing devices such as syringes and spoons). This is particularly beneficial for the administration of antibiotics in pediatric patients or those requiring precise weight-based dosing, including patients with renal and hepatic diseases (Aulton and Taylor 2022). A range of excipients, including suspending agents, antimicrobial preservatives, sweeteners, colorants, and flavoring agents, is required in the formulation of safe, stable, Copyright M. Ways TM. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Pharmacia 72: 1–10 DOI 10.3897/pharmacia.72.e164270 Research Article M. Ways TM: Key excipients and safety concerns in oral antibiotic suspensions2 palatable, and effective suspensions (Aulton and Taylor 2022; Gaikwad et al. 2024). Ideally, the excipients should not have any pharmacological activities or therapeutic uses, although they are used to improve physical stability (no appreciable sedimentation), chemical stability over the required time (shelf life), viscosity, organoleptic properties, and the biopharmaceutical properties of the drug products (Moreton 2010; Elder et al. 2016). Suspending agents are used to maintain the uniform distribution of drug particles in the liquid medium, usually by enhancing the viscosity of the medium, which ensures consistent dosing. Preservatives inhibit microbial growth and ensure the safety and stability of suspensions during storage and use (extending the shelf life after reconstitution) (Rouaz et al. 2021; Bobillot et al. 2024). Sweeteners and flavoring agents provide sweetness to the products, can mask the bitter or metallic taste of antibiotics, and make the suspensions more palatable (especially for children), thereby improving patient compliance. Coloring agents enhance the visual appeal of suspensions, improve patient acceptance, and facilitate product identification (Aulton and Taylor 2022). The safety profile of excipients used in oral suspensions must be considered prior to their use in formulations (Abrantes et al. 2016; Belayneh et al. 2020; Bobillot et al. 2024). Some excipients are used at low concentrations and are therefore unlikely to lead to adverse effects. However, others can trigger fatal anaphylactic or allergic reactions in intolerant individuals or children, even when used at low concentrations (Balbani et al. 2006). Therefore, proper information about excipients, including their names, functional categories, and any adverse effects, must be clearly provided by pharmaceutical manufacturers. This may help in the identification of products with desired physicochemical, biopharmaceutical, and therapeutic properties. The literature lacks data on the type, frequency, and commonality of specific excipients in oral suspensions of antibiotics. To the best of our knowledge, no published study has reported the frequency and commonality of suspending agents in commercially available oral suspensions. Specifically, there is no publicly available research on the excipients used in the formulation of commercially available oral antibiotic suspensions marketed in Sulaymaniyah and the Kurdistan Region of Iraq. This lack of data is compounded by the absence of excipient labeling regulations and inconsistent disclosure practices in the Kurdistan Region and Iraq, which highlights the need for such data. This gap in the literature may have significant implications for both patients and healthcare professionals. Additionally, the lack of data on excipient types can hinder quality control testing (e.g., assay, stability), as understanding excipient composition is essential for accurate evaluation and for selecting appropriate products for specific patient populations. This may also expose patients to high risks of adverse effects, which might not be due to the effects of APIs but to the excipients. Identifying commonly used excipients serves as a benchmark for future formulations, reduces the time and cost associated with developing new products, and provides insight into industry-standard choices, helping drug manufacturers align their formulations with proven practices, regional regulations, and consumer preferences. Such information is also essential for patients, pharmacists, healthcare providers, and regulatory bodies. Given that oral suspensions are predominantly prescribed to pediatric patients, and many of the products include pediatric dosing guidance, excipient selection often reflects considerations of pediatric tolerability, palatability, and safety. The aim of this research was to describe the frequency of suspending agents, preservatives, sweeteners, colorants, and flavoring agents in commercially available oral antibiotic suspensions in Sulaymaniyah, Iraq. In addition to descriptive profiling, the study also analyzed the association between the types of suspending agents and preservatives used and the antibiotic formulations and highlighted selected safety concerns related to the most commonly used excipients. While all samples were collected locally from community pharmacies in Sulaymaniyah, Iraq, the products were manufactured in a range of countries, including Iraq, Syria, Turkey, Jordan, Saudi Arabia, Egypt, India, Switzerland, and Ireland. This diversity reflects the nature of pharmaceutical supply chains in many developing markets, where products from both regional and international manufacturers are commonly distributed. As such, the findings could offer not only an overview of the local pharmaceutical market but also indicative insights into formulation trends encountered in similar healthcare settings. Materials and methods Selection of formulations Oral suspensions containing antibiotics from different classes were selected. Forty-one oral suspensions were included, covering seven broad antibiotic classes: penicillins, penicillins/beta-lactamase inhibitors, cephalosporins, cephalosporins/beta-lactamase inhibitors, macrolides, nitroimidazoles, and sulfonamides/dihydrofolate reductase inhibitors. Within these classes, nine different types of APIs were analyzed. These products were commercially available in local pharmacies of Sulaymaniyah, Kurdistan Region, Iraq. A convenience sampling approach was used, whereby most commercially available oral antibiotic suspensions found in community pharmacies in Sulaymaniyah during the data collection period were included. Multiple brands and dosage strengths of the same API were counted as distinct products to reflect market diversity. The selected antibiotic classes represented the most widely available oral suspensions in local pharmacies during the data collection period; other classes, such as tetracyclines, were not included due to limited availability in suspension form locally. The city was selected based on accessibility and logistical feasibility. While the study was limited to one geographical location, the sample is believed to be representative of the range of products commonly available in the region. Pharmacia 72: 1–10 3 Although the products were not restricted to those exclusively marketed as pediatric formulations, oral suspensions are predominantly prescribed for children, and the majority of the included formulations provided explicit pediatric dosing instructions in their package leaflets. This justified the emphasis on pediatric safety considerations in the analysis and discussion. The products included in this study were intended for oral administration and were available either as ready-to-use oral suspensions or as powders for reconstitution. The frequency of excipients— suspending agents, preservatives, sweeteners, colorants, and flavoring agents—in different products was analyzed based on the information provided in the patient information leaflet (PIL). Only excipients explicitly listed in the product leaflets were included in the analysis; ambiguous or partially disclosed excipients (e.g., unknown flavoring agents) were categorized accordingly, and products lacking identifiable excipient data were excluded from the relevant analysis. Only excipient presence was recorded; no chemical testing or quantitative analysis was conducted. Data were collected and analyzed from August to October 2024. Categorization of excipients for analysis The function of the excipients in the suspensions was determined based on the excipient monographs from the “Handbook of Pharmaceutical Excipients” (Sheskey et al. 2017). Occasionally, some manufacturers provided information on the function of the excipients in the PIL, and this information was also included in the analysis. All excipients that were used as suspending agents, preservatives, sweeteners, colorants, or flavoring agents were identified, and their occurrence and frequency (%) in the formulations were calculated. Statistical analysis Fisher’s exact test was used to evaluate the association between the types of suspending agents or preservatives and the classes of antibiotics in the oral suspensions. This test was selected because it is the most reliable and robust method for categorical data with small sample sizes or sparse distributions, ensuring that the reported associations are statistically valid and interpretable. A p-value of < 0.05 was considered statistically significant. All analyses were performed using IBM SPSS Statistics, version 25. Ethical approval This study was conducted according to the relevant guidelines and regulations and was approved by the Ethics and Research Registration Committee (No. PH136-24) at the College of Pharmacy, University of Sulaimani, Kurdistan Region, Iraq. Results The APIs of the formulations used in this study were amoxicillin, amoxicillin/clavulanate, cefixime, cefdinir, cefpodoxime/clavulanic acid, azithromycin, clarithromycin, metronidazole, and sulfamethoxazole/trimethoprim. Of the 41 formulations analyzed, eight (those containing metronidazole and sulfamethoxazole/trimethoprim) were liquid suspensions, while the other 33 were powders for reconstitution (Table 1). Amoxicillin/clavulanate was the most common API among the studied suspensions, accounting for 24.39% of the formulations, whereas cefpodoxime/clavulanic acid was the least common (2.43%). A total of 12 different suspending agents were identified among the products (Table 2), with several formulations using more than one suspending agent. Xanthan gum was the most commonly used suspending agent, present in 64.5% of the formulations, followed by colloidal silicon dioxide (54.8%), which was often used in combination with xanthan gum (Figs 1, 2). Other suspending agents included sodium carboxymethylcellulose, hydroxypropylcellulose, hydroxypropyl methylcellulose (HPMC), microcrystalline cellulose, maltodextrin, and Tween 80. Less frequently used suspending agents, including povidone K-30, Veegum HV, and Avicel grades 501 and 591, were each identified in only one formulation. Five products (16.1%) did not contain any suspending agents. Additionally, 10 out of the 41 products did not disclose excipient information in the patient information leaflet. A statistically significant association was observed between antibiTable 1. The active pharmaceutical ingredients (APIs), type of pharmaceutical product, frequency, and percentage of formulations analyzed. Class API Pharmaceutical product Frequency of formulations n (%) Penicillins Amoxicillin Powder for reconstitution 6 (14.63) Penicillins/beta-lactamase inhibitors Amoxicillin/clavulanate Powder for reconstitution 10 (24.39) Cephalosporins Cefixime Powder for reconstitution 5 (12.19) Cefdinir Powder for reconstitution 3 (7.31) Cephalosporins/beta-lactamase inhibitors Cefpodoxime/clavulanic acid Powder for reconstitution 1 (2.43) Macrolides Azithromycin Powder for reconstitution 5 (12.19) Clarithromycin Powder for reconstitution 3 (7.31) Nitroimidazoles Metronidazole Liquid suspension 4 (9.75) Sulfonamides/dihydrofolate reductase Sulfamethoxazole/trimethoprim Liquid suspension 4 (9.75) Total 41 (100) Note: Frequency values are presented as n (%); values in parentheses indicate percentages. M. Ways TM: Key excipients and safety concerns in oral antibiotic suspensions4 otic class and the type of suspending agent used (Fisher’s Exact Test, p < 0.001). The contingency table showed that certain agents, such as xanthan gum, were more commonly used in specific antibiotic classes. Full statistical output is provided in the Suppl. material 1: sheet 1. Four different antimicrobial preservatives were identified (Table 3), including sodium benzoate (38.7%), methyl paraben (25.8%), propyl paraben (19.3%), and potassium sorbate (12.9%). Eight formulations (25.8%) did not contain any antimicrobial preservative. Most products contained a single preservative, while a smaller portion used combinations such as methyl paraben with propyl paraben (Figs 3, 4). Fisher’s Exact Test also revealed a significant association between antibiotic class and preservative type (p = 0.001). Some preservatives appeared to be preferentially selected for certain antibiotics, though the distribution was less consistent. Full details are available in the Suppl. material 1: sheet 2. Among the formulations analyzed, six types of sweeteners were identified: sucrose, saccharin sodium, aspartame, Table 2. Types of suspending agents, their frequency, and percentage in the formulations analyzed. Percentages are calculated based on the number of formulations that listed the excipients (N = 31). Suspending agents Frequency in formulations n (%) Xanthan gum 20 (64.5) Colloidal silicon dioxide 17 (54.8) Sodium carboxymethylcellulose 5 (16.1) Hydroxypropylcellulose 5 (16.1) Hydroxypropyl methyl cellulose (hypromellose, HPMC) 4 (12.9) Tween 80 4 (12.9) Microcrystalline cellulose 3 (9.6) Maltodextrin 3 (9.6) Povidone k-30 1 (3.2) Veegum HV(magnesium aluminum silicate) 1 (3.2) Avicel 501 1 (3.2) Avicel 591 1 (3.2) No suspending agents 5 (16.1) Note: Frequency values are presented as n (%); values in parentheses indicate percentages. Figure 2. Number of oral antibiotic suspensions containing suspending agents used as single agents or in combination. 0 5 10 15 20 25 Single Combinaon Number Suspending agent 0 1 2 3 4 5 6 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 Frequency Formulaon Xanthan gum CSD SCMCHPC HPMCTween 80 MCC Maltodextrin Povidone k-30 Veegum HV Avicel 591 Avicel 501 Figure 1. Frequency of suspending agents used in the oral antibiotic suspensions applied either individually or in combination. CSD: colloidal silicon dioxide, SCMC: sodium carboxymethylcellulose, HPC: hydroxypropylcellulose, HPMC: hydroxypropyl methylcellulose, MCC: microcrystalline cellulose. Each formulation is coded as F1 to F26 to represent the 26 individual products analyzed. Pharmacia 72: 1–10 5 sodium cyclamate, sorbitol, and monoammonium glycyrrhizinate (Table 3). Sucrose was the most frequently used sweetener, found in 26 products (83.8%). One product did not contain any sweetener. While 15 products contained only sucrose, others included combinations of two or more sweeteners. Three products contained three sweeteners, and only one product contained four sweeteners. With respect to colorant use, only some amoxicillin and cefdinir suspensions and all of the clarithromycin suspensions contained colorants. Six synthetic colorants were identified: titanium dioxide, Sunset Yellow FCF, erythrosine, Allura Red AC, Ponceau 4R, and yellow food-grade color. In total, 23 formulations (74.1%) did not contain any colorants (Table 3). Finally, 16 different flavoring agents were found among the formulations (Table 4). Strawberry was the most common (22.5%), followed by banana flavor. Fruit-based flavors such as raspberry, orange, lemon, cherry, and mixed fruit were frequently used. In some products of amoxicillin, cefdinir, clarithromycin, Table 3. Types of antimicrobial preservatives, sweeteners, and colorants, their frequency, and percentage in the formulations analyzed. Percentages are calculated based on the number of formulations that listed the excipients (N = 31). Antimicrobial preservatives Frequency in formulations n (%) Sweeteners Frequency in formulations n (%) Colorants Frequency in formulations n (%) Sodium benzoate 12 (38.7) Sucrose 26 (83.8) Titanium dioxide 3 (9.6) Methyl paraben 8 (25.8) Saccharin sodium 12 (38.7) Sunset yellow FCF (FD&C* yellow No. 6) 2 (6.4) Propyl paraben 6 (19.3) Aspartame 3 (9.6) Erythrosine (FD&C Red No. 3) 1 (3.2) Potassium sorbate 4 (12.9) Sorbitol 3 (9.6) Allura red AC (FD&C Red No. 40) 1 (3.2) No antimicrobial preservatives 8 (25.8) Sodium cyclamate 1 (3.2) Ponceau 4R 1 (3.2) Monoammonium glycyrrhizinate 1 (3.2) Yellow color food grade 1 (3.2) No sweeteners 1 (3.2) No colorants 23 (74.1) Note: Frequency values are presented as n (%); values in parentheses indicate percentages. *FD&C = Food, Drugs, and Cosmetics; used in the United States to indicate that a colorant is certified for use in foods, drugs, and cosmetics by the U.S. FDA. Figure 4. Number of oral antibiotic suspensions containing preservatives used as single agents or in combination. 0 2 4 6 8 10 12 14 16 18 Singl eC ombinaon Number Preservave Figure 3. Frequency of preservatives used in the oral antibiotic suspensions applied either individually or in combination. Each formulation is coded as F1 to F23 to represent the 23 individual products analyzed. 0 0.5 1 1.5 2 2.5 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10F11 F12F13 F14F15 F16F17 F18F19 F20F21 F22F 23 Frequency Formulaon Sodium benzoate Methyl parabenPropyl paraben Potassium sorbate M. Ways TM: Key excipients and safety concerns in oral antibiotic suspensions6 metronidazole, and sulfamethoxazole/trimethoprim, flavoring agents such as citric acid anhydrous and trisodium citrate were also included to improve palatability. One metronidazole formulation did not contain any flavoring agent despite its known bitterness. Furthermore, 9.6% of the products contained unspecified flavoring agents. Discussion This study aimed to analyze the types and frequency of commonly used excipients—particularly suspending agents, preservatives, sweeteners, colorants, and flavoring agents—in commercially available oral suspensions of antibiotics, with a focus on their formulation rationale and implications for safety, particularly in pediatrics, and product acceptability. Given that oral suspensions are predominantly used in pediatric patients, excipient-related safety risks were interpreted in light of pediatric susceptibility, particularly for preservatives, sweeteners, and colorants. The predominance of powder-for-reconstitution suspensions in this study can be attributed to the instability of many antibiotics in aqueous media. Only metronidazole and sulfamethoxazole/trimethoprim were marketed as liquid suspensions, as they are chemically stable in aqueous environments under appropriate pH and temperature conditions (Mathew et al. 1994; Białk-Bielińska et al. 2012; Donnelly and Ying 2015). In contrast, antibiotics such as amoxicillin and cephalosporins degrade more rapidly in water (D’Costa and Wright 2009; Bahmany et al. 2023), and formulating them as powders for reconstitution significantly improves their shelf life. Incomplete or inconsistent labeling of excipients remains a significant barrier to evaluating the safety and quality of pharmaceutical products. In our study, 24% of oral antibiotic suspensions lacked excipient disclosure. This issue was even more pronounced in a study conducted in Nigeria, where 51% of pediatric oral liquid formulations did not disclose excipient information, reflecting a common challenge in pharmaceutical labeling across different regions (Soremekun et al. 2019). Suspending agents are essential in maintaining uniformity and physical stability in oral suspensions. In this study, a diverse range of suspending agents was identified, often used in combination to optimize rheology and prevent sedimentation. Xanthan gum was the most frequently used, likely due to its high viscosity, thermal stability, and compatibility across pH ranges (Sheskey et al. 2017; Layek 2024). Colloidal silicon dioxide, often paired with xanthan gum, acts synergistically to enhance viscosity and prevent caking. Other agents such as hydroxypropylcellulose, HPMC, sodium carboxymethylcellulose, and Tween 80 are well known for their relative biocompatibility, non-toxicity, and ability to form stable suspensions. Less frequently used suspending agents, such as Veegum HV and Avicel grades, may be reserved for specific formulation needs or excluded due to potential mucosal irritation or cost considerations. For example, Veegum HV may cause mucosal or respiratory irritation if not properly handled. Veegum HV is reserved for formulations requiring high stability and viscosity in challenging conditions, such as acidic or high ionic strength environments, which may not be necessary in most antibiotic suspensions (López-Galindo and Viseras 2004; López-Galindo et al. 2007; Ali et al. 2010). The absence of suspending agents in some products raises questions regarding post-reconstitution physical stability and dosing accuracy, particularly critical for pediatric formulations. The significant association between suspending agent and antibiotic class may reflect excipient compatibility with specific drug properties. For example, the frequent use of xanthan gum, either alone or in combination, in cephalosporin suspensions may relate to its favorable rheological properties and ability to maintain physical stability in aqueous formulations. However, variations could also stem from manufacturer-specific formulation strategies rather than pharmacological requirements. Overall, the findings emphasize the widespread use of polymeric suspending agents and the frequent reliance on combinations to achieve desirable suspension characteristics. Antimicrobial preservatives play a critical role in preventing contamination during use, particularly in multi-dose products. Sodium benzoate was the most common preservative, due to its cost-effectiveness, acceptable safety profile, and broad-spectrum activity. Parabens (methyl and propyl) were also commonly used, often in combination to enhance antimicrobial efficacy. These parabens are esters of p-hydroxybenzoic acid and are widely employed in Table 4. Types of flavoring agents, their frequency, and percentage in the formulations analyzed. Percentages are calculated based on the number of formulations that listed the excipients (N = 31). Flavoring agents Frequency in formulations n (%) Strawberry flavor 7 (22.5) Banana flavor 6 (19.3) Citric acid anhydrous 5 (16.1) Raspberry flavor 5 (16.1) Mix fruit flavor 5 (16.1) Orange flavor 4 (12.9) Unknown flavoring agent 3 (9.6) Lemon flavor 2 (6.4) Vanilla flavor 2 (6.4) Vanillin 1 (3.2) Trisodium citrate 1 (3.2) Cream caramel 1 (3.2) Citric acid monohydrate 1 (3.2) Cream flavors 1 (3.2) Cherry flavor 1 (3.2) Tangerine liquid flavor 1 (3.2) No flavoring agents 1 (3.2) Note: Frequency values are presented as n (%); values in parentheses indicate percentages. Pharmacia 72: 1–10 7 pharmaceutical, food, and cosmetic products for preservation. Our findings align with a Nigerian study, which also reported methylparaben, propylparaben, and sodium benzoate as common preservatives in pediatric oral liquids (Soremekun et al. 2019). Several excipients identified in our study, such as sodium benzoate and parabens, are associated with adverse effects or regulatory safety limits in pediatric populations. Sodium benzoate, for example, poses a particular risk in neonates due to its ability to displace bilirubin from albumin, potentially leading to hyperbilirubinemia and kernicterus, especially in those with immature metabolic pathways. Additionally, limited capacity to metabolize benzoic acid in infants under 8 weeks raises concerns about its accumulation and toxicity, which necessitates caution even at levels within the accepted daily intake (European Medicines Agency 2017). Parabens, including methylparaben and propylparaben, while widely used, have defined acceptable daily intakes due to concerns about their potential biological effects, including endocrine disruption such as interference with estrogen and testosterone regulation observed in animal studies. Although such effects have not been confirmed in humans, they are of particular concern in pediatric populations, where the endocrine system is still developing and may be more vulnerable to disruption (European Medicines Agency 2015). These findings raise potential safety concerns and underscore the importance of excipient choice and labeling of pharmaceutical products distributed in Sulaymaniyah and across the broader Kurdistan Region. The predominance of single-agent preservative use suggests a formulation preference for simpler antimicrobial strategies, likely to reduce potential drug–excipient interactions or regulatory complexity. However, combinations of preservatives may be employed to broaden antimicrobial coverage or enhance preservative efficacy through synergistic effects. In line with our findings, Balbani et al. (2006) found that methylparaben was the most common antimicrobial preservative in oral preparations (45.2%), and sodium benzoate was present in 32.8% of the preparations. There are controversies regarding the use of parabens; however, many studies have demonstrated that parabens are non-teratogenic, non-mutagenic, and non-carcinogenic, and that real evidence for their toxicity in humans has not been established (Ma et al. 2016; Petric et al. 2021). Potassium sorbate, though effective, was less frequently used. The absence of preservatives in a large number of the formulations raises safety concerns, especially in the absence of antimicrobial efficacy testing. While the association between preservative type and antibiotic class was statistically significant (p = 0.001), it should be interpreted cautiously due to the small sample size. Factors such as product pH, sugar content, and regulatory preferences likely influence preservative selection more than the antibiotic itself. The observed patterns may reflect formulation traditions rather than microbiological necessity. However, future studies with larger datasets and stratified analyses are needed to explore potential associations between excipient selection and antibiotic class while accounting for confounding factors such as manufacturer-specific formulation practices. Sweeteners were present in nearly all formulations, with sucrose dominating due to its dual role in enhancing taste and increasing viscosity, which aids in the stability of suspensions. While sucrose enhances both taste and viscosity, its high content in pediatric formulations may contribute to dental caries and unhealthy sugar exposure, and its use is discouraged by the American Heart Association (Vos et al. 2017). The inclusion of multiple sweeteners in some formulations reflects efforts to mask unpleasant tastes, particularly for pediatric compliance (Walsh et al. 2014). The identification of sweeteners not listed in the FDA Inactive Ingredients Database, such as sodium cyclamate and monoammonium glycyrrhizinate (FDA 2024), warrants further evaluation regarding their safety and regulatory acceptance. Sodium cyclamate is banned in the United States due to earlier safety concerns but remains permitted in some countries under specific intake limits. Its inclusion in pediatric medicines may reflect regional regulatory allowances or cost considerations. However, given the limited pediatric safety data for such additives, their use should follow international pharmaceutical guidelines, such as those issued by the EMA, WHO, and FDA. Colorants were limited to a small number of formulations, typically those with amoxicillin, cefdinir, or clarithromycin. All identified colorants were synthetic. Most, including titanium dioxide, Sunset Yellow FCF, erythrosine, and Allura Red AC, are approved by the U.S. FDA for use in foods, drugs, and cosmetics. (FDA 2022). Ponceau 4R is not approved for use in the United States, although it is permitted in other regions such as the European Union. One colorant, labeled only as “yellow food-grade color,” could not be clearly identified and may not correspond to a specific FDA-approved colorant. Although FDA-approved colorants are generally regarded as safe, there are some concerns about their impact on human health, and the search for alternatives—for example, natural colorants—is also encouraged (Pérez-Ibarbia et al. 2016; Hancock et al. 2024). However, the issue of poor stability of natural colorants could prevent their use in pharmaceutical formulations. Titanium dioxide was the most commonly used colorant, likely due to its aesthetic appeal, opacity, high chemical stability, biocompatibility, and low toxicity (Fei Yin et al. 2013). However, recent concerns regarding its potential genotoxicity, particularly in the EU, have prompted calls to limit its use (Abend et al. 2024). The majority of the products were colorant-free, which aligns with European regulatory recommendations that advise minimizing excipients of known adverse effect, including synthetic dyes, especially in pediatric formulations where some colorants have been associated with behavioral effects such as hyperactivity (European Medicines Agency 2006). M. Ways TM: Key excipients and safety concerns in oral antibiotic suspensions8 Flavoring agents were varied and dominated by fruit flavors, which aligns with pediatric preferences, as children prefer fruit flavors over traditional flavoring agents such as menthol and capsicum (Eccles 2020). Strawberry and banana were the most common. Additional excipients such as citric acid and trisodium citrate were used to mask the taste of bitter APIs. The absence of a flavoring agent in one metronidazole product is notable, considering the known bitterness of this API (Gadalla et al. 1984). The presence of unspecified flavoring agents in several products may raise safety concerns for sensitive populations and reflects a lack of transparency in excipient disclosure. This emphasizes the need for stricter regulatory standards requiring the full listing of all excipients, including flavoring agents, to enhance patient safety and informed clinical decision-making. Flavoring agents may include allergens or complex mixtures that are not adequately evaluated in children. Clear disclosure is essential to avoid unintentional exposure and to align with regulatory standards. The findings of the current study highlight inconsistencies in excipient selection and labeling in oral antibiotic suspensions and point to the need for improved adherence to regulatory guidelines, particularly regarding safety disclosure, avoidance of excipients with known risk, and formulation transparency. In light of these findings, it is important to consider how current regulatory frameworks guide the selection and disclosure of excipients in pharmaceutical products. The European Medicines Agency has outlined excipient-related safety concerns, urging manufacturers to evaluate risks on a case-by-case basis and to avoid potentially harmful excipients when possible (European Medicines Agency 2006). Furthermore, the European Commission’s guideline on excipient labeling mandates the disclosure of excipients known to have a recognized action or effect in all patients, with special attention to their impact on vulnerable groups such as pediatric populations (European Commission 2003). Despite these regulatory efforts, implementation remains inconsistent, particularly in low-regulation countries, including Iraq, where imported and locally manufactured products may not uniformly follow such standards. The U.S. Food and Drug Administration’s Inactive Ingredient Database (FDA 2024) also serves as a useful benchmark for excipient acceptability, though pediatric-specific exposure data remain limited. These regulatory documents provide important guidance for ensuring formulation safety, and our findings underscore the gap between such standards and real-world excipient use in oral antibiotic suspensions in Sulaymaniyah and the broader Kurdistan Region. Although the study is geographically limited, the inclusion of products from multiple international manufacturers enhances the relevance of the findings to other markets with comparable pharmaceutical sourcing and regulatory contexts. A limitation of this study is the reliance on leaflet-disclosed excipient lists, which may not always reflect the full composition of the formulations. Additionally, the information in PILs may not always be updated to reflect the most recent formulation changes. Moreover, undeclared excipients, especially those used as suspending agents, preservatives, or colorants, may affect safety interpretations. However, in this study, the inclusion criteria ensured that only products with adequate excipient disclosure were analyzed. The safety-related discussion in this study is qualitative in nature. As excipient concentrations were not provided in most PILs, no quantitative safety assessments could be made. Additionally, functional classification of excipients was primarily based on typical excipient roles reported in the literature and standard references, rather than on experimental verification or manufacturer-specified functions, which could introduce uncertainty regarding the actual function of each excipient in the final product. We acknowledge that these methodological constraints limit the depth of interpretability of the findings. Nonetheless, despite the reliance on PIL data and the relatively small sample size, the study provides a systematic and regionally representative evaluation of excipient usage patterns in oral antibiotic suspensions, offering insights that are both methodologically robust within these limitations and practically relevant. Conclusion This study provides essential new information on the types, frequency, and combination patterns of excipients used in the formulation of oral suspensions of antibiotics. Xanthan gum, sodium benzoate, sucrose, titanium dioxide, and strawberry flavor were the most common excipients identified. Notably, many products used combinations of suspending agents or preservatives, with xanthan gum and colloidal silicon dioxide being the most frequently co-used suspending agents. In contrast, single preservatives were more commonly used than combinations. Our findings offer valuable insights for clinicians, pharmacists, and formulators when considering the safety, efficacy, and acceptability of oral suspensions of antibiotics. Furthermore, identifying trends in excipient combinations (e.g., xanthan gum with colloidal silicon dioxide as suspending agents) can guide rational formulation development, which is especially important for pediatric populations where product stability, safety, and palatability are critical. Although this study focused on suspensions available in Sulaymaniyah, future research comparing excipient use across different regions and product types may reveal broader trends and enhance formulation strategies. Additionally, the findings underscore the need for complete and consistent disclosure of excipient content in the patient information leaflet, which is essential for regulatory transparency, informed clinical decisions, and improved public health—particularly for children, as oral suspensions are commonly used in pediatric care. Pharmacia 72: 1–10 9 Acknowledgments The author thanks the University of Sulaimani for their support in conducting this study. Additional information Conflict of interest The author has declared that no competing interests exist. Ethical statements The authors declared that no clinical trials were used in the present study. The authors declared that no experiments on humans or human tissues were performed for the present study. The authors declared that no informed consent was obtained from the humans, donors or donors’ representatives participating in the study. The authors declared that no experiments on animals were performed for the present study. 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