This report identifies those medicines available over the counter (OTC) that have the potential to cause drowsiness, and therefore the potential to be hazardous to drivers and other road users. The authors identified a total of 102 medicines for the treatment of coughs and colds, allergies, pain, nausea and gastrointestinal upsets, all with the potential to cause sedation. These medicines fall into three main groups, antihistamines (of which there are three sub-groups), opioids and muscarinic antagonists. From the literature it is clear that the antihistamines cause the most sedation. One sub-group, the classical H1-receptor antihistamines are particularly sedating, and are even used for the relief of temporary sleep disturbance in some instances. The impairment caused by the recommended doses of at least two of these drugs is greater than that caused by the legal blood alcohol concentration limit for driving in this country. Each class of drug was reviewed individually. The elderly are particularly vulnerable to the sedative effects of these drugs. In old age, renal dysfunction develops. The excretion rate of these drugs decreases and drug accumulation occurs within the body. Recommended doses of drugs that normally do not cause impairment, will begin to cause drowsiness and affect performance in these people. Many of the medicines we examined do not carry specific warnings for the elderly. The interactions between drugs were also considered. The majority of the reviewed substances enhanced the sedating effect of ethanol. A person impaired in this way, but still legally allowed to drive, is a potential hazard to themselves and other road users. It is highly likely that people will combine several OTC drugs for the treatment of an ailment. It is often the belief that as medicines contain different compounds they will not have an additive sedating effect; this is not the case. Representative OTC preparations were purchased for each class of drug. We investigated the labelling on these medicines, warning the consumer of potentially sedative effects. This labelling was not consistent. Several medicines that were recommended by the British National Formulary (BNF) to have such labelling, had none on the packaging. Even within classes of medicine there appears to be no labelling consistency. Several mentioned drowsiness as a side effect on the package insert, but no mention of this was made on the exterior packaging. The labelling of OTC medicines liable to cause drowsiness, needs to be more closely monitored. (Author/publisher)
Samenvatting