Nausea antihistamine-anticholinergic drugs

Cyclizine has antimuscarinic properties and is a potent anti-emetic, effective for the control of postoperative and drug-induced nausea and vomiting. It has been used to prevent motion sickness, although diphenhydramine and promethazine are more effective. It is available in oral and parenteral formulations. In contrast to many other first-generation antihistamines sedation is not marked. It is available in tablet form as the hydrochloride and in injectable form as the lactate. Because of its anticholinergic action, blurred vision and dry mouth are associated with clinical doses. When given by rapid intravenous injection tachycardia may be a problem. Meclozine is a related drug which, like cyclizine, is used primarily for motion sickness. 

Anticholinergics are associated with many side effects including mood change, confusion, hallucinations, drowsiness, and cardiac irregularity.13,39 In addition, blurred vision, dryness of the mouth, nausea/ vomiting, constipation, and urinary retention are fairly common. Antihistamine drugs with anticholinergic properties are also used occasionally (Table 10-2). 

Phenothiazines such as prochlorperazine, thiethylperazine, and chlorpromazine see Chapter 18) are among the most commonly used antinauseants and antiemetics. Their principal mechanism of action is dopamine receptor antagonism at the CTZ. Compared to metoclopramide or ondansetron see above), these drugs do not appear to be as uniformly effective in cancer chemotherapy-induced emesis. On the other hand, they also possess antihistaminic and anticholinergic activities, which are of value in other forms of nausea, such as motion sickness. 

The drug acts by exerting appreciable anticholinergic and antihistaminic activities. Besides, it possesses CN S-depressant profile. Hence, indicated for the control and management of nausea, vomitting and dizziness closely related to motion sickness. 

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