Quantification of Ethanol Content in Traditional Herbal Cough Syrups

Introduction: The use of alcohol as an excipient in pharmaceutical preparations raises safety concerns, especially when used in high concentration. This study aims to scrutinize the ethanol concentration in traditional herbal cough syrups available over-the-counter (OTC) in Malaysia. Method: Enzymatic analysis was adopted to estimate the alcohol contents of five selected syrups. The principle reaction involved ethanol oxidation by nicotinamide-adenine dinucleotide (NAD) in the presence of the enzyme alcohol dehydrogenase (ADH), forming acetaldehyde, reduced NAD (NADH) and a proton. The ethanol concentration of each syrup was quantitatively determined by detecting NADH using UV spectrophotometry at detection wavelength of 340 nm. Results: The ethanol percentage by volume (% v/v) in the tested syrups ranges from 0.102% to 2.576%. All five syrups studied comply with the FDA requirement for drugs for adults and children >6 years since they do not contain more than 5% ethanol. However, three syrups do not fulfil the requirement for use in children <6 years as they contain higher than 0.5% ethanol, yet they are inappropriately indicated on their packaging for use in children >3 years. In terms of safety, all studied syrups fulfil European Medicine Agency’s (EMA) recommendation as they will not induce a blood alcohol concentration (BAC) higher than 0.125g/L after a single dose. Nevertheless, none of these syrups comply with Malaysian Drug Registration Guidance on labelling requirements as they do not disclose their alcohol contents on the packaging. Conclusion: More rigorous regulation on alcohol content in herbal preparations, and disclosure of alcohol content in product packagings should be enforced.