"The US Food and Drug Administration (FDA) has approved an extended-release capsule formulation of carbidopa-levodopa (Rytary, IPX066, Impax Pharmaceuticals) for the treatment of Parkinson's disease (PD), postencephalitic parkinsonism, an"...
When SINEMET (carbidopa-levodopa) is to be given to patients who are being treated with levodopa, levodopa must be discontinued at least twelve hours before therapy with SINEMET (carbidopa-levodopa) is started. In order to reduce adverse reactions, it is necessary to individualize therapy. See DOSAGE AND ADMINISTRATION section before initiating therapy.
The addition of carbidopa with levodopa in the form of SINEMET (carbidopa-levodopa) reduces the peripheral effects (nausea, vomiting) due to decarboxylation of levodopa; however, carbidopa does not decrease the adverse reactions due to the central effects of levodopa. Because carbidopa permits more levodopa to reach the brain and more dopamine to be formed, certain adverse CNS effects, e.g., dyskinesias (involuntary movements), may occur at lower dosages and sooner with SINEMET (carbidopa-levodopa) than with levodopa alone.
Levodopa alone, as well as SINEMET (carbidopa-levodopa) , is associated with dyskinesias. The occurrence of dyskinesias may require dosage reduction.
As with levodopa, SINEMET (carbidopa-levodopa) may cause mental disturbances. These reactions are thought to be due to increased brain dopamine following administration of levodopa. All patients should be observed carefully for the development of depression with concomitant suicidal tendencies. Patients with past or current psychoses should be treated with caution.
As with levodopa, care should be exercised in administering SINEMET (carbidopa-levodopa) to patients with a history of myocardial infarction who have residual atrial, nodal, or ventricular arrhythmias. In such patients, cardiac function should be monitored with particular care during the period of initial dosage adjustment, in a facility with provisions for intensive cardiac care.
As with levodopa, treatment with SINEMET (carbidopa-levodopa) may increase the possibility of upper gastrointestinal hemorrhage in patients with a history of peptic ulcer.
Neuroleptic Malignant Syndrome (NMS)
Sporadic cases of a symptom complex resembling NMS have been reported in association with dose reductions or withdrawal of therapy with SINEMET (carbidopa-levodopa) . Therefore, patients should be observed carefully when the dosage of SINEMET (carbidopa-levodopa) is reduced abruptly or discontinued, especially if the patient is receiving neuroleptics.
NMS is an uncommon but life-threatening syndrome characterized by fever or hyperthermia. Neurological findings, including muscle rigidity, involuntary movements, altered consciousness, mental status changes; other disturbances, such as autonomic dysfunction, tachycardia, tachypnea, sweating, hyper- or hypotension; laboratory findings, such as creatine phosphokinase elevation, leukocytosis, myoglobinuria, and increased serum myoglobin have been reported.
The early diagnosis of this condition is important for the appropriate management of these patients. Considering NMS as a possible diagnosis and ruling out other acute illnesses (e.g., pneumonia, systemic infection, etc.) is essential. This may be especially complex if the clinical presentation includes both serious medical illness and untreated or inadequately treated extrapyramidal signs and symptoms (EPS). Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever, and primary central nervous system (CNS) pathology.
The management of NMS should include: 1) intensive symptomatic treatment and medical monitoring and 2) treatment of any concomitant serious medical problems for which specific treatments are available. Dopamine agonists, such as bromocriptine, and muscle relaxants, such as dantrolene, are often used in the treatment of NMS, however, their effectiveness has not been demonstrated in controlled studies.
As with levodopa, periodic evaluations of hepatic, hematopoietic, cardiovascular, and renal function are recommended during extended therapy.
Patients with chronic wide-angle glaucoma may be treated cautiously with SINEMET (carbidopa-levodopa) provided the intraocular pressure is well-controlled and the patient is monitored carefully for changes in intraocular pressure during therapy.
Dopaminergic agents, including levodopa, may be associated with somnolence and very rarely episodes of sudden onset of sleep. In some cases, these episodes may occur without awareness or warning during daily activities. Patients must be informed of this and advised to exercise caution while driving or operating machines while being treated with dopaminergic agents, including levodopa. Patients who have experienced somnolence and/or an episode of sudden sleep onset must refrain from driving or operating machines (see PATIENT INFORMATION).
Epidemiological studies have shown that patients with Parkinson's disease have a higher risk (2- to approximately 6-fold higher) of developing melanoma than the general population. Whether the increased risk observed was due to Parkinson's disease or other factors, such as drugs used to treat Parkinson's disease, is unclear.
For the reasons stated above, patients and providers are advised to monitor for melanomas frequently and on a regular basis when using SINEMET (carbidopa-levodopa) for any indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists).
Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, SCOT (AST), SGPT (ALT), lactic dehydrogenase, and bilirubin. Abnormalities in blood urea nitrogen and positive Coombs test have also been reported. Commonly, levels of blood urea nitrogen, creatinine, and uric acid are lower during administration of SINEMET (carbidopa-levodopa) than with levodopa.
SINEMET (carbidopa-levodopa) may cause a false-positive reaction for urinary ketone bodies when a test tape is used for determination of ketonuria. This reaction will not be altered by boiling the urine specimen. False-negative tests may result with the use of glucose-oxidase methods of testing for glucosuria.
Cases of falsely diagnosed pheochromocytoma in patients on carbidopa-levodopa therapy have been reported very rarely. Caution should be exercised when interpreting the plasma and urine levels of catecholamines and their metabolites in patients on levodopa or carbidopa-levodopa therapy.
Carcinogenesis, Mutagenesis, Impairment of Fertility
In a two-year bioassay of SINEMET (carbidopa-levodopa) , no evidence of carcinogenicity was found in rats receiving doses of approximately two times the maximum daily human dose of carbidopa and four times the maximum daily human dose of levodopa.
In reproduction studies with SINEMET (carbidopa-levodopa) , no effects on fertility were found in rats receiving doses of approximately two times the maximum daily human dose of carbidopa and four times the maximum daily human dose of levodopa.
Pregnancy Category C. No teratogenic effects were observed in a study in mice receiving up to 20 times the maximum recommended human dose of SINEMET (carbidopa-levodopa) . There was a decrease in the number of live pups delivered by rats receiving approximately two times the maximum recommended human dose of carbidopa and approximately five times the maximum recommended human dose of levodopa during organogenesis. SINEMET (carbidopa-levodopa) caused both visceral and skeletal malformations in rabbits at all doses and ratios of carbidopa/levodopa tested, which ranged from 10 times/5 times the maximum recommended human dose of carbidopa/levodopa to 20 times/10 times the maximum recommended human dose of carbidopa/levodopa.
There are no adequate or well-controlled studies in pregnant women. It has been reported from individual cases that levodopa crosses the human placenta! barrier, enters the fetus, and is metabolized. Carbidopa concentrations in fetal tissue appeared to be minimal. Use of SINEMET (carbidopa-levodopa) in women of childbearing potential requires that the anticipated benefits of the drug be weighed against possible hazards to mother and child.
In a study of one nursing mother with Parkinson's disease, excretion of levodopa in human breast milk was reported. Therefore, caution should be exercised when SINEMET (carbidopa-levodopa) is administered to a nursing woman.
Safety and effectiveness in pediatric patients have not been established. Use of the drug in patients below the age of 18 is not recommended.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 3/28/2011
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