• Neuroleptics used to alleviate symptoms of major psychiatric disorders

PHENOTHIAZINES

Chlorpromazine (Largactil); Modecate

• Prior to their introduction, psychotic patients were institutionalised

• Act by blocking action of dopamine in certain parts of the brain

• Has antipsychotic, sedative, antihistaminic & anti emetic action

• Also anticholinergic, alpha blocking & direct cardiac depressant activity

• When initially inject iv: drop in BP 2° peripheral vasodilation & central depression

• IV injection must be slow with 5mg usually adequate

• Depresses temperature regulation & suppresses shivering

• Adverse Reactions:

Sedation

Anticholinergic: dry mouth, constipation, urinary retention

Cardiovascular: Changes in ECG, hypotension

Extrapyramidal: drug induced parkinsonian, akathisia [motor restlessness], acute dystonic reactions [eg laryngeal or bronchial spasm], tardive dyskinesia

Drugs: May potentiate anticholinergic drug effects [atropine]

In phenothiazine induced hypotension, adrenaline should not be used as phenothiazine may reverse its effect resulting in exacerbated hypotension; noradrenaline is more appropriate

BUTYROPHENONES

Haloperidol (Serenace); Droperidol

• Not related chemically to phenothiazines

• Similar mechanism of action to phenothiazines

• Mild alpha blocker

• Dropoeridol is slowly metabolised & has a prolonged action (12 hours)

• Induces a state of mental detachment, tranquillity & catatonia

• Combination with a narcotic provides suitable conditions for operations of control of ventilation in ICU

• Side effects include hypotension & extrapyramidal reactions

• Butyrophenone induced hypotension should be treated with IV fluids and dopamine or noradrenaline. Adrenaline should not be used since serenace may reverse its action and cause profound hypotension