Caution should be observed when using metoclopramide in patients taking other drugs that can also cause extrapyramidal reactions, such as the phenothiazines. Increased toxicity may occur if metoclopramide is used in patients receiving lithium, and in caution is advisable with other centrally active drugs such as antiepileptics. Antimuscarinics and opioid analgesics antagonise the gastrointestinal effects of metoclopramide. The absorption of other drugs may be affected by metoclopramide; it may either diminish absorption from the stomach (as with digoxin) or enhance absorption from the small intestine. It inhibits serum cholinesterase and may prolong neuromuscular blockade produced by suxamethonium and mivacurium. Metoclopramide may also increase prolactin blood concentrations and therefore interfere with drugs which may have a hypoprolactinaemic effect such as bromocriptine. It has been suggested that it should not be given to patients receiving MAIOs.