OTC sleep aids are primarily based on which type of substance?

OTC sleep aids are primarily based on antihistamines, which are commonly used in over-the-counter sleep medications due to their sedative properties. Antihistamines work by blocking histamine, a substance in the body that promotes wakefulness, leading to drowsiness. This makes them effective for short-term relief of occasional sleeplessness.

In contrast, prescription medications often involve different classes of drugs, such as benzodiazepines or other controlled substances, which are not typically available over the counter. Stimulants, on the other hand, are substances that enhance alertness and energy, making them counterproductive for promoting sleep. Analgesics are pain relievers and do not have sedative effects relevant to promoting sleep. Thus, antihistamines are the primary substances used in OTC sleep aids because of their specific action on sleep regulation.