Sedative-Hypnotic Agents: Nonprescription Agents

Nonprescription Agents

There are a number of over-the-counter (OTC) sleep aids used by patients suffering from insomnia (see Table 81.1). These agents typically contain the histamine (H₁) receptor antagonist diphen-hydramine (e.g., Benadryl, Sominex) or some other sedating anti-histamine such as doxylamine (e.g., Nytol, Unisom). While these agents often cause significant drowsiness due to their antihis-taminic properties, their effectiveness in treating insomnia has not been clearly established in randomized, placebo-controlled studies. They tend to have a prolonged duration of action leading to sedation and slowed reaction times during the day following their use. In addition, tachyphylaxis often develops within sev-eral days to a week or two limiting their use to only those patients with short-term problems with insomnia.

The OTC antihistamines are also highly anticholinergic and therefore may cause dry mouth, constipation, urinary reten-tion and delirium quite easily. Geriatric patients are particularly susceptible to these anticholinergic effects. Patients already on other medications with significant anticholinergic activity should take these compounds quite judiciously as the anticholinergic ef-fects could be magnified.

The common practice of combining an analgesic such as as-pirin or acetaminophen and an antihistamine (e.g., Tylenol PM) is no more effective than the use of an antihistamine alone unless pain is present. As such, their use cannot be recommended for patients suffering from insomnia when pain is not a major complaint.

Melatonin is a naturally occurring pineal gland peptide hormone that is available in OTC formulations from a number of manufacturers. The Food and Drug Administration (FDA) classifies melatonin as a nutritive or dietary supplement. The Dietary Supplement Health and Education Act does not require dietary supplements to be reviewed by the FDA and, as a re-sult, the strength and purity of melatonin cannot be guaranteed. When purified or synthesized and taken orally, melatonin alters circadian rhythms, lowers core body temperature, and reduces daytime alerting phenomena originating in the suprachiasmatic nucleus. Some clinicians feel that melatonin may be particularly effective when the normal circadian cycle is disrupted (e.g., jet lag, shift work). A number of studies have yielded conflicting results regarding the efficacy and long-term safety of melatonin. Efficacy data may be somewhat conflicting due to the lack of solid data regarding appropriate dosing strategies. Efficacy has been reported with doses as low as 0.3 mg at bedtime. While there are no known long-term safety issues associated with the use of melatonin, treatment-emergent side effects include pruri-tus, tachycardia, headache and daytime drowsiness.