Issues related to monitoring the safety of over-the-counter (OTC) medicines

Abstract

Pharmaceutical advances over the past 50 years have benefited many people in terms of disease prevention and management. However, probably without exception, most pharmaceutical products can cause adverse consequences of varying severity and frequency. In the last 10 years, many medicines that were originally prescription only have now become available over the counter (OTC), either from pharmacies or other general retail outlets. The volume and value of OTC medicine sales have increased accordingly. These switches have been well regulated and based on clear criteria and evidence of safety. Benefits of the changes include increased convenience to patients, greater self-management of minor ailments and a reduction in government drug expenditure.However, there are important differences between medicines supplied OTC and on medical prescription. With OTC medicines there is generally less healthcare professional input into the recommendation or ongoing monitoring of use. There is an absence of records per se, or linkage to other medication records elsewhere, and most countries allow direct-to-consumer advertising of the product. Taken together these differences can result in inappropriate expectations, demand and use of the OTC medicines, with limited opportunity for ongoing patient follow-up and monitoring of safety. Methodologies for pharmacy-based epidemiological studies of OTC medicines need to be developed. Studies should be large enough to detect associations that might exist, and to consider other explanations for associations such as chance, bias or confounding. There have already been some pilot studies with encouraging results with respect to follow-up rates. Outcome data however have usually been self-reported and the studies have lacked a suitable comparison group. Purchasers and suppliers of OTC medicines should also be made aware of, and encouraged to use, existing systems for spontaneous reporting of suspected adverse events, such as the Yellow Card Scheme in the UK. While available OTC medicines are perceived to be generally safe, problems have occasionally arisen with some earlier switched products (e.g. terfenadine). There have also been concerns about some traditional herbal and homeopathic remedies such as St John's wort. While such adverse events are rare, they emphasise the need for healthcare professionals and the public to understand and manage such risks. Many doctors are unaware of the range of OTC preparations available, and therefore do not consider them as a possible cause of presenting symptoms. Neither do they take them into account when making a new prescribing decision. The public need to be aware that OTC medicines should be treated with the same care as prescribed medicines, and that advice on recommended dose, contraindications and interactions should be adhered to.