Dosages of concomitantly administered opioids should be reduced by approximately half, because levomepromazine amplifies the therapeutic actions and side-effects of opioids. Combination with tramadol (Ultram) is associated with increased risk of seizures.
Additive sedative effects and confusional states may emerge if levomepromazine is given with benzodiazepines or barbiturates. This may be avoided by using the lowest dose possible with the substances in question.
Exert particular caution in combining levomepromazine with other anticholinergic drugs (tricyclic antidepressants and antiparkinsonian-agents): Particularly the elderly may develop delirium, high fever, severe obstipation, even ileus and glaucoma. Reduce both the dose of levomepromazine and the dose of the other drug. If possible, avoid such combinations.
Caffeine and/or stimulantes of the ephedrine/amphetamine type may counteract the specific actions of levomepromazine. Concomitant use of these substances should be avoided.
Coffee and black tea should be avoided because they decrease the absorption of levomepromazine considerably. The same is true for antacids; these should be given 1 to 2 hours before or after oral administration of leveomepromazine.