levodopa-carbidopa, Sinemet, Sinemet CR, Parcopa (cont.)

DRUG INTERACTIONS: The use of amantadine (Symmetrel), benztropine (Cogentin), procyclidine (Kemadrin), or trihexyphenidyl (Artane) with carbidopa-levodopa can enhance the anti- Parkinson's effects of levodopa. Droperidol, haloperidol (Haldol), loxapine (Loxitane), metoclopramide (Reglan), phenothiazines such as prochlorperazine (Thorazine); thioxanthenes as thiothixene (Navane) inhibit dopamine in the brain. These drugs, therefore, can worsen Parkinson's disease and reverse the beneficial effects of levodopa. Methyldopa (Aldomet) and reserpine also can interfere with the beneficial actions of carbidopa-levodopa and can increase the risk of side effects.

The occurrence of postural hypotension (reduced blood pressure when standing from a sitting or lying down position) may increase when carbidopa-levodopa is combined with drugs that reduce blood pressure. Phenytoin (Dilantin) can increase the break-down of carbidopa-levodopa, reducing its effectiveness. Use of carbidopa-levodopa with monoamine oxidase inhibitors (MAOI's) antidepressants, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane), can result in severe and dangerous elevations in blood pressure. MAOI's should be stopped 2-4 weeks before starting carbidopa-levodopa therapy.

The side effects associated with levodopa, including dizziness upon rising, confusion, movement disorders, nausea, and hallucinations, all can be increased by selegiline (Eldepryl).

PREGNANCY: Although there are no human studies that have examined the effects of carbidopa-levodopa on the fetus, animal studies have shown adverse effects. Therefore, in prescribing carbidopa-levodopa for a pregnant woman, the treating physician must weigh the potential risks to the fetus against the potential benefits to the mother.



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