Mechanism of action of sedating antihistamines


Relatively new are the 5HT3 agents (Zofran, Kytril).

In theory, these agents might not be ideal for emesis related to vestibular imbalance.

H3 receptor agonists appear to cause the same result as blockade of H2 receptors.

Most antihistamines also have calcium channel blocking effect (according to Timmerman, 1994).

Unfortunately, astemizole does not appear to be generally useful as it is ineffective in preventing motion sickness (Kohl et al, 1987) and because it has significant potential toxicity.

There is evidence for involvement of several types of histamine receptors.

A discussion of drug treatment should start with a discussion of the neurotransmitters used to signal in the vestibular system. Vestibular suppressant and antiemetic drugs are the mainstay of treatment of vertigo.Phenothiazines, such as prochlorperazine (Compazine) and promethazine (Phenergan), are effective antiemetics, probably because of their dopamine blocking activity, but they also act at other sites. Because these drugs can induce significant side effects, such as dystonia, they are considered second-line drugs whose use should be brief and cautious.Drugs that speed gastric emptying, such as metoclopramide (Reglan) and powdered ginger root may be helpful in managing emesis (Grontved et al, 1988).Diphenidol (Vontrol), is also an anticholinergic, although little used in the US.There are also some reports of scopolamine inducing migraine, as well as a withdrawall syndrome.Long acting benzodiazepines are not helpful for relief of vertigo.

You must have an account to comment. Please register or login here!