Visual hallucinations induced by the combination of prolintane and diphenhydramine.

The case of a young man is presented who developed visual hallucinations following two months of concomitant use of prolintane and diphenhydramine at therapeutic dosages. An increase in dopaminergic brain activity is proposed as the causal mechanism for hallucinations--whereas prolintane can induce the release of dopamine at the synaptic cleft, diphenhydramine can act inhibiting the reuptake of dopamine and inducing a potentiation of its effects. The psychiatric complications appearing two months after starting the use of both drugs could be attributed to a phenomenon of pharmacological kindling.