May counteract the antihypertensive effects of guanethidine, betanidine, reserpine, clonidine & methyldopa. Increased risk of paralytic ileus, hyperpyrexia w/ TCAs. May enhance the effects of alcohol, barbiturates & other CNS depressants. May increase risk of QT prolongation & malignant arrhythmias w/ drugs known to increase plasma conc of flupentixol & cause electrolyte disturbances. Increased risk of neurotoxicity w/ lithium. May reduce the effect & increased risk of cardiac side effects of levodopa.