Sinemet Cr
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Questions & Answers
Side Effects & Adverse Reactions
When patients are receiving levodopa without a decarboxylase inhibitor, levodopa must be discontinued at least twelve hours before SINEMET CR is started. In order to reduce adverse reactions, it is necessary to individualize therapy. See DOSAGE AND ADMINISTRATION section before initiating therapy.
SINEMET CR should be substituted at a dosage that will provide approximately 25% of the previous levodopa dosage (see DOSAGE AND ADMINISTRATION).
Carbidopa does not decrease adverse reactions due to central effects of levodopa. By permitting more levodopa to reach the brain, particularly when nausea and vomiting is not a dose-limiting factor, certain adverse central nervous system (CNS) effects, e.g., dyskinesias, will occur at lower dosages and sooner during therapy with SINEMET CR than with levodopa alone.
Patients receiving SINEMET CR may develop increased dyskinesias compared to SINEMET. Dyskinesias are a common side effect of carbidopa levodopa treatment. The occurrence of dyskinesias may require dosage reduction.
All patients should be observed carefully for the development of depression with concomitant suicidal tendencies.
SINEMET CR should be administered cautiously to patients with severe cardiovascular or pulmonary disease, bronchial asthma, renal, hepatic or endocrine disease.
As with levodopa, care should be exercised in administering SINEMET CR 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 CR may increase the possibility of upper gastrointestinal hemorrhage in patients with a history of peptic ulcer.
Patients taking SINEMET CR alone or with other dopaminergic drugs have reported suddenly falling asleep without prior warning of sleepiness while engaged in activities of daily living (includes operation of motor vehicles). Road traffic accidents attributed to sudden sleep onset have been reported. Although many patients reported somnolence while on dopaminergic medications, there have been reports of road traffic accidents attributed to sudden onset of sleep in which the patient did not perceive any warning signs, such as excessive drowsiness, and believed that they were alert immediately prior to the event. Sudden onset of sleep has been reported to occur as long as one year after the initiation of treatment.
Falling asleep while engaged in activities of daily living usually occurs in patients experiencing pre-existing somnolence, although some patients may not give such a history. For this reason, prescribers should reassess patients for drowsiness or sleepiness especially since some of the events occur well after the start of treatment. Prescribers should be aware that patients may not acknowledge drowsiness or sleepiness until directly questioned about drowsiness or sleepiness during specific activities. Patients should be advised to exercise caution while driving or operating machines during treatment with SINEMET CR. Patients who have already experienced somnolence or an episode of sudden sleep onset should not participate in these activities during treatment with SINEMET CR.
Before initiating treatment with SINEMET CR, advise patients about the potential to develop drowsiness and ask specifically about factors that may increase the risk for somnolence with SINEMET CR such as the use of concomitant sedating medications and the presence of sleep disorders. Consider discontinuing SINEMET CR in patients who report significant daytime sleepiness or episodes of falling asleep during activities that require active participation (e.g., conversations, eating, etc.). If treatment with SINEMET CR continues, patients should be advised not to drive and to avoid other potentially dangerous activities that might result in harm if the patients become somnolent. There is insufficient information to establish that dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living.
Sporadic cases of a symptom complex resembling neuroleptic malignant syndrome (NMS) have been reported in association with dose reductions or withdrawal of certain antiparkinsonian agents such as levodopa, carbidopa levodopa and carbidopa levodopa extended release. Therefore, patients should be observed carefully when the dosage of 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.
Legal Issues
There is currently no legal information available for this drug.
FDA Safety Alerts
There are currently no FDA safety alerts available for this drug.
Manufacturer Warnings
There is currently no manufacturer warning information available for this drug.
FDA Labeling Changes
There are currently no FDA labeling changes available for this drug.
Uses
SINEMET CR is indicated in the treatment of Parkinson's disease, post-encephalitic parkinsonism, and symptomatic parkinsonism that may follow carbon monoxide intoxication or manganese intoxication.
History
There is currently no drug history available for this drug.
Other Information
SINEMET® CR (carbidopa levodopa) is a sustained-release combination of carbidopa and levodopa for the treatment of Parkinson's disease and syndrome.
Carbidopa, an inhibitor of aromatic amino acid decarboxylation, is a white, crystalline compound, slightly soluble in water, with a molecular weight of 244.3. It is designated chemically as (—)-L-α-hydrazino-α-methyl-β-(3,4-dihydroxybenzene) propanoic acid monohydrate. Its empirical formula is C10H14N2O4•H2O, and its structural formula is:
Tablet content is expressed in terms of anhydrous carbidopa, which has a molecular weight of 226.3.
Levodopa, an aromatic amino acid, is a white, crystalline compound, slightly soluble in water, with a molecular weight of 197.2. It is designated chemically as (—)-L-α-amino-β-(3,4-dihydroxybenzene) propanoic acid. Its empirical formula is C9H11NO4, and its structural formula is:
SINEMET CR is supplied as sustained-release tablets containing either 50 mg of carbidopa and 200 mg of levodopa, or 25 mg of carbidopa and 100 mg of levodopa. Inactive ingredients are hydroxypropyl cellulose, magnesium stearate, and hypromellose. SINEMET CR 25-100 and SINEMET CR 50-200 also contain FD&C Blue #2/Indigo Carmine AL and FD&C Red #40/Allura Red AC AL.
The 50-200 tablet is supplied as an oval, compressed tablet that is dappled-purple in color and is coded "521" on one side and plain on the other. The 25-100 tablet is supplied as an oval, compressed tablet that is dappled-purple in color and is coded "601" on one side and plain on the other. The SINEMET CR tablet is a polymeric-based drug delivery system that controls the release of carbidopa and levodopa as it slowly erodes. SINEMET CR 25-100 is available to facilitate titration when 100 mg steps are required.
Sources
Sinemet Cr Manufacturers
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Merck Sharp & Dohme Corp.
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Sinemet Cr | Merck Sharp & Dohme Corp.
SINEMET CR contains carbidopa and levodopa in a 1:4 ratio as either the 50-200 tablet or the 25-100 tablet. The daily dosage of SINEMET CR must be determined by careful titration. Patients should be monitored closely during the dose adjustment period, particularly with regard to appearance or worsening of involuntary movements, dyskinesias or nausea. SINEMET CR should not be chewed or crushed.
Standard drugs for Parkinson's disease, other than levodopa without a decarboxylase inhibitor, may be used concomitantly while SINEMET CR is being administered, although their dosage may have to be adjusted.
Since carbidopa prevents the reversal of levodopa effects caused by pyridoxine, SINEMET CR can be given to patients receiving supplemental pyridoxine (vitamin B6).
Initial DosagePatients currently treated with conventional carbidopa levodopa preparations: Studies show that peripheral dopa-decarboxylase is saturated by the bioavailable carbidopa at doses of 70 mg a day and greater. Because the bioavailabilities of carbidopa and levodopa in SINEMET and SINEMET CR are different, appropriate adjustments should be made, as shown in Table 2.
Table 2: Approximate Bioavailabilities at Steady State* Tablet Amount of
Levodopa (mg)
in Each Tablet Approximate
Bioavailability Approximate Amount
of Bioavailable
Levodopa (mg) in
Each Tablet * This table is only a guide to bioavailabilities since other factors such as food, drugs, and inter-patient variabilities may affect the bioavailability of carbidopa and levodopa. † The extent of availability of levodopa from SINEMET CR was about 70-75% relative to intravenous levodopa or standard SINEMET in the elderly. ‡ The extent of availability of levodopa from SINEMET was 99% relative to intravenous levodopa in the healthy elderly. SINEMET CR
50-200
200
0.70-0.75†
140-150 SINEMET
25-100
100
0.99‡
99Dosage with SINEMET CR should be substituted at an amount that provides approximately 10% more levodopa per day, although this may need to be increased to a dosage that provides up to 30% more levodopa per day depending on clinical response (see DOSAGE AND ADMINISTRATION, Titration with SINEMET CR). The interval between doses of SINEMET CR should be 4-8 hours during the waking day. (See CLINICAL PHARMACOLOGY, Pharmacodynamics.)
A guideline for initiation of SINEMET CR is shown in Table 3.
Table 3: Guidelines for Initial Conversion from SINEMET to SINEMET CR * For dosing ranges not shown in the table see DOSAGE AND ADMINISTRATION, Initial Dosage — Patients currently treated with conventional carbidopa levodopa preparations. SINEMET
Total Daily Dose*
Levodopa (mg) SINEMET CR
Suggested
Dosage Regimen 300-400 200 mg b.i.d. 500-600 300 mg b.i.d. or 200 mg t.i.d. 700-800 A total of 800 mg in 3 or more divided doses (e.g., 300 mg a.m., 300 mg early p.m., and 200 mg later p.m.) 900-1000 A total of 1000 mg in 3 or more divided doses (e.g., 400 mg a.m., 400 mg early p.m., and 200 mg later p.m.)Patients currently treated with levodopa without a decarboxylase inhibitor: Levodopa must be discontinued at least twelve hours before therapy with SINEMET CR is started. SINEMET CR should be substituted at a dosage that will provide approximately 25% of the previous levodopa dosage. In patients with mild to moderate disease, the initial dose is usually 1 tablet of SINEMET CR 50-200 b.i.d.
Patients not receiving levodopa: In patients with mild to moderate disease, the initial recommended dose is 1 tablet of SINEMET CR 50-200 b.i.d. Initial dosage should not be given at intervals of less than 6 hours.
Titration with SINEMET CRFollowing initiation of therapy, doses and dosing intervals may be increased or decreased depending upon therapeutic response. Most patients have been adequately treated with doses of SINEMET CR that provide 400 to 1600 mg of levodopa per day, administered as divided doses at intervals ranging from 4 to 8 hours during the waking day. Higher doses of SINEMET CR (2400 mg or more of levodopa per day) and shorter intervals (less than 4 hours) have been used, but are not usually recommended.
When doses of SINEMET CR are given at intervals of less than 4 hours, and/or if the divided doses are not equal, it is recommended that the smaller doses be given at the end of the day.
An interval of at least 3 days between dosage adjustments is recommended.
MaintenanceBecause Parkinson's disease is progressive, periodic clinical evaluations are recommended; adjustment of the dosage regimen of SINEMET CR may be required.
Addition of Other Antiparkinson MedicationsAnticholinergic agents, dopamine agonists, and amantadine can be given with SINEMET CR. Dosage adjustment of SINEMET CR may be necessary when these agents are added.
A dose of carbidopa levodopa immediate release 25-100 or 10-100 (one half or a whole tablet) can be added to the dosage regimen of SINEMET CR in selected patients with advanced disease who need additional immediate-release levodopa for a brief time during daytime hours.
Interruption of TherapySporadic cases of hyperpyrexia and confusion have been associated with dose reductions and withdrawal of SINEMET or SINEMET CR.
Patients should be observed carefully if abrupt reduction or discontinuation of SINEMET CR is required, especially if the patient is receiving neuroleptics. (See WARNINGS.)
If general anesthesia is required, SINEMET CR may be continued as long as the patient is permitted to take oral medication. If therapy is interrupted temporarily, the patient should be observed for symptoms resembling NMS, and the usual dosage should be administered as soon as the patient is able to take oral medication.
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