Pharmacology for Anaesthesia and Intensive Care

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18 Antiemetics and related drugs

Vomiting

centre

CTZ

Vomiting

Dopamine

Limbic cortex

Peripheral pain

pathways

Drugs 5-HT

Vestibular

apparatus

Cardiovascular and

abdominal afferents

(vagal)

Figure 18.1.Summary of the various neural inputs that result in vomiting.

Dopamine antagonists

Phenothiazines

Phenothiazines are the main group of anti-psychotic drugs (neuroleptics) and have

only a limited role in the treatment of vomiting. They are divided into three groups on

the basis of structure, which confers typical pharmacological characteristics (Table

18.1).

Chlorpromazine

Chlorpromazine’s proprietary name ‘Largactil’ hints at the widespread effects of this

drug.

Uses

Chlorpromazine is used in schizophrenia for its sedative properties and to cor-

rect altered thought. Its effects on central neural pathways are complicated but are

thought to involve isolating the reticular activating system from its afferent con-

nections. This results in sedation, disregard of external stimuli and a reduction in

motor activity (neurolepsy). It is sometimes used to control vomiting or pain in ter-

minal care where other agents have been unsuccessful. It has also been shown to be

effective in preventing PONV. It is occasionally used to treat hiccup.