Sinemet Side Effects

Generic Name: carbidopa / levodopa

Note: This document contains side effect information about carbidopa / levodopa. Some of the dosage forms listed on this page may not apply to the brand name Sinemet.

Some side effects of Sinemet may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to carbidopa / levodopa: oral conventional tablets, oral extended-release tablets, oral orally disintegrating tablets

Side effects include:

Dyskinesias (choreiform, dystonic, other adventitious movements), nausea.

For Healthcare Professionals

Applies to carbidopa / levodopa: oral tablet, oral tablet disintegrating, oral tablet extended release

General

Although the optimal timing of the initiation of levodopa therapy is controversial, some investigators have suggested that early treatment of parkinsonism with levodopa delays disease progression and decreases mortality.

Adverse effects attributable to levodopa occur frequently regardless of whether carbidopa is taken concomitantly or not. In contrast, carbidopa is fairly well tolerated and is rarely reported to cause adverse effects. Carbidopa may reduce the incidence of vomiting, nausea and anorexia in patients treated with levodopa. Carbidopa, however, does not alter the frequency of central adverse effects.

Nervous system

Choreiform movements due to levodopa therapy may occur in as many as 80% of patients treated for one year and frequently involve facial grimacing, exaggerated chewing and twisting and protrusion of the tongue.

Several types of motor fluctuations may occur and result in "bradykinetic episodes". Some motor fluctuations are related to the timing of dosage administration. For example, patients may experience "peak of the dose dyskinesia" and a wearing-off effect called "end of the dose akinesia". The "wearing-off" may result in early morning dystonia. Such motor fluctuations may be managed by increasing the frequency of dose administration and decreasing the dose administered (or possibly by use of extended release formulations) to achieve a smoother therapeutic effect.

Other motor fluctuations are not related to the timing of dose administration. Such fluctuations are characterized by sudden loss of levodopa effect which may last for minutes to hours and result in akinesia followed by a sudden return of levodopa effect. These "on-off" fluctuations may occur many times per day. "On-off" fluctuations may respond to more frequent dose administration.

Finally, akinesia paridoxica is a sudden episode of akinesia which occurs as patients begin to walk. Akinesia paridoxica frequently results in falls and often responds to levodopa dose reductions.

Other adverse nervous system effects due to levodopa include myoclonus, sleep disturbances (including insomnia, daytime somnolence, altered dreams and episodic nocturnal myoclonus), Meige's syndrome (blepharospasm-oromandibular dystonia) and ocular dyskinesia. In addition, the orofacial movements induced by levodopa have occasionally been reported to cause severe dental erosion.

Some investigators have suggested that levodopa may cause brain dysfunction and may have negative effects on cognitive performance.

Levodopa "drug holidays" have been proposed by some investigators as potentially beneficial (perhaps by causing dopamine receptor resensitization). However, the therapeutic value of these drug holidays is controversial.

Nervous system effects occur in as many as 50% of treated patients on long-term therapy and include involuntary movements and mental status changes most frequently. The types of involuntary movements due to levodopa have been characterized as choreiform, dystonic and dyskinetic. Fluctuations in motor function occur frequently and often increase as the duration of therapy increases.

Gastrointestinal

Exacerbation of preexisting ulcer disease with severe upper gastrointestinal bleeding has been reported.

Gastrointestinal side effects including nausea and vomiting are the most common adverse gastrointestinal effects of levodopa. Anorexia and, rarely, gastrointestinal hemorrhage have been reported.

Psychiatric

Psychiatric effects include hallucinations (particularly visual hallucinations), psychosis, confusion, anxiety, mania, hypomania, depression, rapid mood cycling, nightmares, and hypersexuality.

Some authors have suggested that clozapine may be useful in the management of levodopa-induced psychotic symptoms.

Other investigators have suggested that levodopa may induce alterations in the noradrenergic systems of the CNS which may lead to panic attacks.

Other

Fever, altered consciousness, autonomic dysfunction and muscle rigidity are the hallmarks of the neuroleptic malignant syndrome. The neuroleptic malignant syndrome (NMS) is associated with a case fatality rate of about 20%. If withdrawal of dopaminergic therapy is suspected as the cause of NMS, dopaminergic therapy should be restarted. If a neuroleptic agent is suspected as the cause, the neuroleptic agent should be immediately discontinued. For patients with NMS suspected to be due to neuroleptic therapy, consideration should be given to dantrolene (or bromocriptine) administration. Intensive monitoring and supportive care are indicated for all patients with NMS.

Sudden discontinuation or rapid tapering of levodopa therapy may result in acute worsening of parkinsonism or, less frequently, in a syndrome resembling the neuroleptic malignant syndrome. Cases of psychologic levodopa addiction have also been reported rarely.

Cardiovascular

Cardiovascular effects include hypotension and syncope. Arrhythmias have also been reported rarely.

Some authors have reported marked hemodynamic and clinical improvements in patients with congestive heart failure treated with oral levodopa. However, at least one author has reported marked hemodynamic deterioration following such treatment.

Dermatologic

Dermatologic side effects including a number of cases of malignant melanoma have been reported in patients taking levodopa for Parkinson's Disease. Additionally, several cases of maculopapular skin rashes have been reported in patients taking levodopa-containing drugs.

Despite reports of melanoma occurring in levodopa-treated patients, some authors have suggested that a causal association is tenuous and other authors have suggested that levodopa may have an antitumor effect on melanoma. Nevertheless, the manufacturers of levodopa-containing drugs report that either the history of melanoma or the presence of suspicious skin lesions is a contraindication for the use of levodopa-containing drugs.

One author has suggested that some rashes reported in association with levodopa therapy may be related to the presence of a yellow dye in Sinemet 25/100.

Immunologic

Immunologic side effects including rare lupus-like syndrome have been suggested by some authors.

Hematologic

Hematologic side effects including severe hemolytic and nonhemolytic anemias have been reported rarely.

Respiratory

Respiratory dyskinesias (occasionally of life-threatening severity) have been reported.

Hepatic

Hepatic effects including asterixis (without abnormalities of liver function tests) have been reported rarely. The manufacturer of levodopa-containing products report that abnormal liver function tests may occur.

Endocrine

Endocrine side effects including elevated urinary vanillylmandelic acid levels during levodopa therapy have occasionally let to confusion concerning the diagnosis of pheochromocytoma.

Renal

Renal side effects including Hypokalemia and hyponatremia have been reported. Chronic administration of levodopa may also slightly but significantly increase BUN without changes in the glomerular filtration rate.

Hypersensitivity

Hypersensitivity, type III, adverse effects have been reported in a 68-year-old man with Parkinson's after the use of carbidopa-levodopa, which manifested as purpura of the limbs, vasculitis and glomerulonephritis. The diagnosis of Henoch-Schonlein syndrome was confirmed after drug rechallenge.

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