Myung In Haloperidol Drug Interactions

Concomitant use of haloperidol and CNS depressants such as analgesics and barbiturates, hypnotics, strong anesthetics, sedative, antihistamine, hypotensive drug and anticholinergic drug, the contact of alkylphosphates, and alcohol may potentiate the interaction. Therefore, it should be used with caution and the haloperidol dose may need to be decreased.
Haloperidol may antagonize the action of epinephrine and other sympathomimetic agents and reverse the blood pressure lowering effects of adrenergic-blocking agents such as guanethidine and clonidine. Haloperidol should not be given with this agent.
Haloperidol may decrease the antiparkinson effects of levodopa. Therefore, haloperidol should not be given with levodopa.
An enhanced CNS effect, when combined with methyldopa, has been reported.
ECG pattern changes, severe extrapyramidal symptoms, tardive dyskinesia, neuroleptic malignant syndrome (NMS), irreversible brain damage during combined treatment with lithium and haloperidol have been reported. It is recommended that lithium levels should always be maintained below 1 mmol/l when combined with haloperidol. One report has suggested that ECG monitoring might be advisable. If unexplained pyrexia occurs in the presence of extrapyramidal side-effects both lithium and haloperidol should be stopped immediately.
When prolonged treatment with enzyme inducing drugs such as carbamazepine, phenobarbital, this results in a significant reduction of haloperidol plasma levels. Therefore, during combination treatment, the haloperidol dose should be adjusted.
Haloperidol inhibits the metabolism of tricyclic antidepressants, thereby increasing plasma levels of these drugs.
Prolonged QT ventricular arrhythmia during combined treatment with terfenadine, astemizole may occur.
In pharmacokinetic studies mild to moderately increased haloperidol levels have been reported when haloperidol was given concomitantly with the following drugs: quinidine, buspirone, and fluoxetine. It may be necessary to reduce the haloperidol dosage.
If an antiparkinson agent is used concomitantly with haloperidol, an increase of anticholinergic effect promotes tardive dyskinesia.
Because haloperidol is badly absorbed, when combined with antacid, caffeine, therapeutic effects may be decreased.