Dementia methyldopa + haloperidol

The hypotensive effects of methyldopa and haloperidol might be expected to be additive. The CNS effects are not understood, although methyldopa can cause sedation, depression and dementia, and haloperidol can cause... 

Dementia occurred when methyldopa was combined with haloperidol (59). 

Thornton WE. Dementia induced by methyldopa with haloperidol. N Engl J Med 1976 294(22) 1222. 

Two patients who had been taking methyldopa 1 to 1.5 g daily for hypertension, without problems, developed a dementia syndrome (cognitive disabilities, loss of memory, disorientation, etc.) within 3 days of starting to take haloperidol 6 to 8 mg daily for anxiety. The symptoms totally cleared within 72 hours of stopping the haloperidol. Another patient treated with haloperidol for schizophrenia, and methyldopa for hypertension, became very irritable and aggressive. When the methyldopa was replaced with hydrochlorothiazide, the patient s behaviour improved dramatically. ... 

Diuretics and alcohol increase the hypotensive action of methyldopa (37 ). Ox-prenolol too is said to augment the hypotensive action, rendering it possible to reduce methyldopa dosage and thereby lowering the incidence of side effects (54< ). Interaction between methyldopa and haloperidol, both of which affect dopamine in the CNS, was found to result in an acute dementia in 2 patients who received the drugs simultaneously. The condition was reversible, and the mental condition was again normal 3 days after withdrawal of the haloperidol (148 ). 

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