DIPHENHYDRAMINE (BENADRYL)
Diphenhydramine is an antihistamine used for treating allergy, hay fever, and symptoms of the common cold. It also prevents and treats insomnia, nausea, and vomiting. It should not be used for insomnia in children and is not for use at all in children younger than 2 years.
CHEMICAL NAME
diphenhydramine (2-(diphenylmethoxy)-n, N-dimethylethylamine hydrochloride)
MEDICINES
Diphenhydramine is an antihistamine that works as an H1-receptor antagonist and was initially used for symptomatic relief of allergic symptoms caused by histamine. Today it is also used to prevent or treat insomnia and is found, for example, in the medicines Nytol, Sominex, and Tylenol PM.
HOW IT WORKS
Diphenhydramine prevents histamine from docking with the H1-receptors.
SIDE EFFECTS
Used correctly, anti-motion-sickness medicines containing diphenhydramine prevent nausea and dizziness. They work by blocking the effect of a neurotransmitter called acetylcholine, which transmits signals between the ear’s balance center and the part of the brain that is involved in nausea and vomiting. An overdose may result in drowsiness, blurred vision, rapid heart rate, confusion, seizures, or coma. Other symptoms may include dry mouth, nausea, vomiting, unsteadiness, high blood pressure, as well as hallucinations. Patients who take an overdose or use diphenhydramine over a long period may experience serious mental complications and dementia-type symptoms. Other complications, such as pneumonia, muscle damage from lying on a hard surface for an extended period of time, or brain damage from a lack of oxygen, can result in permanent disability. Few people die from an antihistamine overdose, but it can precipitate serious heart rhythm disturbances that can lead to death. In general: Because diphenhydramine may cause dizziness or drowsiness, it is best to take it at bedtime. The effects may continue into the next day, therefore users should not drive or operate machinery until they feel fully alert.
INTERACTIONS
Combining monoamine oxidase inhibitors (antidepressants) with diphenhydramine can increase certain side effects that are produced by the latter, such as constipation, drowsiness, and difficulty urinating.
PROPER USE
As a sleep aid, 50 mg of diphenhydramine should be taken 30 minutes before bedtime. Seven to eight hours of sleep are required to ensure the medicine (and its soporific effect) have cleared out of the body. Patients who suffer from nausea and vomiting may prefer to use diphenhydramine in suppository form. The suppository would need to be softened and moistened in cold water. If too soft, it can be chilled in the refrigerator. If the person is vomiting, oral administration is not advised.