Carbidopa/levodopa is unlikely to cause high blood pressure (hypertension). It was reported in less than 1% of patients in clinical trials and is not considered a common adverse reaction related to the drug.

However, there have been rare instances of high blood pressure among patients who take both carbidopa/levodopa and tricyclic antidepressants, a class of antidepressant medications that includes Asendin (amoxapine) and Sinequan (doxepin).

Similarly, high blood pressure may occur if patients on carbidopa/levodopa are simultaneously taking or have recently taken Nardil (phenelzine), Parnate (tranylcypromine) or any other nonselective monoamine oxidase inhibitor (MAOI)—another type of antidepressant.

Orthostatic hypotension, or low blood pressure that occurs when standing up, can also be a rare side effect of carbidopa/levodopa. Orthostatic hypotension may occur in patients taking carbidopa/levodopa who also take certain medications to lower their blood pressure (antihypertensive drugs) or selective MAO-B inhibitors such as Azilect (rasagiline) and Eldepryl and Zelapar (selegiline).

Orthostatic hypotension may be indicated by symptoms including:

• Nausea
• Sweating
• Dizziness
• Fainting

To prevent episodes of orthostatic hypotension, it is helpful to stand up slowly and carefully after lying or sitting down.