Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Accord-UK Ltd (Trading style: Accord), Whiddon Valley, Barnstaple, Devon, EX32 8NS
*Pharmacotherapeutic group: *Phenothiazines with piperazine structure.
ATC code: NO5AB04
Prochlorperazine maleate is a phenothiazine.
Prochlorperazine has a wide range of activity arising from its depressant actions on the CNS and its alpha-adrenergic blocking and weaker anti-muscarinic properties. It inhibits dopamine and prolactin-release-inhibitory factor, thus stimulating the release of prolactin. The turnover of dopamine in the brain is increased. There is evidence that the antagonism of central dopaminergic function is related to the therapeutic effect in psychotic conditions.
Prochlorperazine has sedative properties but tolerance to the sedation usually develops rapidly. Prochlorperazine has anti-emetic, anti-pruritic, serotonin-blocking, and weak antihistamine properties and slight ganglion-blocking activity. It inhibits the heat regulating centre, can relax smooth muscle and has membrane stabilising and hence local anaesthetic properties. Its actions on the autonomic system produce vasodilatation, hypotension and tachycardia. Salivary and gastric secretions are reduced.
Prochlorperazine is well absorbed from the GI tract but is subject to considerable first pass metabolism from the gut wall. It is also extensively metabolised in the liver and is excreted in the urine and bile. Plasma concentrations following oral administration are much lower than those following intramuscular injection, and are subject to wide inter-subject variation. There is no simple correlation between plasma concentrations of prochlorperazine and its metabolites, and therapeutic effect.
Prochlorperazine may be metabolised by hydroxylation and conjugation with glucuronic acid, N-oxidation, oxidation of the sulfur atom and dealkylation. Plasma half-life is reported to be only a few hours but elimination of the metabolites may be very prolonged. Prochlorperazine is extensively bound to plasma proteins, widely distributed in the body (it crosses the blood/brain barrier) and its metabolites cross the placental barrier and are excreted in milk. The rate of metabolism and excretion decreases in old age.
Not applicable.
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