<p>Symptomatic postural hypotension may occur when levodopa is added to the treatment of patients already receiving antihypertensive. Dose adjustment of the antihypertensive agent may be required. Dopamine receptor antagonists (e.g. some antipsychotics and antiemetics), phenytoin and papaverine may reduce the therapeutic effect of levodopa. Patients taking these medicinal products with levodopa/ carbidopa/ entacapone combination should be carefully observed for loss of therapeutic response. Since levodopa competes with certain amino acids, the absorption of Levodopa, Carbidopa &amp; Entacapone&nbsp;may be impaired in some patients on high protein diet.</p>