SINEMET CR (Page 4 of 5)

The following adverse experiences have been reported in post-marketing experience with SINEMET CR:

Cardiovascular: Cardiac irregularities, syncope.

Gastrointestinal: Taste alterations, dark saliva.

Hypersensitivity: Angioedema, urticaria, pruritus, bullous lesions (including pemphigus-like reactions).

Nervous System/Psychiatric: Neuroleptic malignant syndrome (see WARNINGS), increased tremor, peripheral neuropathy, psychotic episodes including delusions and paranoid ideation, pathological gambling, increased libido including hypersexuality, impulse control symptoms.

Skin: Alopecia, flushing, dark sweat.

Urogenital: Dark urine.

Other adverse reactions that have been reported with levodopa alone and with various carbidopa-levodopa formulations and may occur with SINEMET CR are:

Cardiovascular: Phlebitis.

Gastrointestinal: Gastrointestinal bleeding, development of duodenal ulcer, sialorrhea, bruxism, hiccups, flatulence, burning sensation of tongue.

Hematologic: Hemolytic and nonhemolytic anemia, thrombocytopenia, leukopenia, agranulocytosis.

Hypersensitivity: Henoch-Schonlein purpura.

Metabolic: Weight gain, edema.

Nervous System/Psychiatric: Ataxia, depression with suicidal tendencies, dementia, euphoria, convulsions (however, a causal relationship has not been established); bradykinetic episodes, numbness, muscle twitching, blepharospasm (which may be taken as an early sign of excess dosage; consideration of dosage reduction may be made at this time), trismus, activation of latent Horner’s syndrome, nightmares.

Skin: Malignant melanoma (see also CONTRAINDICATIONS), increased sweating.

Special Senses: Oculogyric crises, mydriasis, diplopia.

Urogenital: Urinary retention, priapism.

Miscellaneous: Faintness, hoarseness, malaise, hot flashes, sense of stimulation, bizarre breathing patterns.

Laboratory Tests: Abnormalities in alkaline phosphatase, SGOT (AST), SGPT (ALT), bilirubin, Coombs test, uric acid.

OVERDOSAGE

Management of acute overdosage with SINEMET CR is the same as with levodopa. Pyridoxine is not effective in reversing the actions of SINEMET CR.

General supportive measures should be employed, along with immediate gastric lavage. Intravenous fluids should be administered judiciously and an adequate airway maintained. Electrocardiographic monitoring should be instituted and the patient carefully observed for the development of arrhythmias; if required, appropriate antiarrhythmic therapy should be given. The possibility that the patient may have taken other drugs as well as SINEMET CR should be taken into consideration. To date, no experience has been reported with dialysis; hence, its value in overdosage is not known.

Based on studies in which high doses of levodopa and/or carbidopa were administered, a significant proportion of rats and mice given single oral doses of levodopa of approximately 1500-2000 mg/kg are expected to die. A significant proportion of infant rats of both sexes are expected to die at a dose of 800 mg/kg. A significant proportion of rats are expected to die after treatment with similar doses of carbidopa. The addition of carbidopa in a 1:10 ratio with levodopa increases the dose at which a significant proportion of mice are expected to die to 3360 mg/kg.

DOSAGE AND ADMINISTRATION

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 50-200 may be administered as whole or as half-tablets which should not be chewed or crushed. SINEMET CR 25-100 may be used in combination with SINEMET CR 50-200 to titrate to the optimum dosage, or as an alternative to the 50-200 half-tablet.

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 Dosage

Patients 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 II.

Table II: Approximate Bioavailabilities at Steady State
Tablet Amount ofLevodopa (mg)in Each Tablet ApproximateBioavailability Approximate Amountof BioavailableLevodopa (mg) inEach 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 (Carbidopa-Levodopa) in the elderly.
††† The extent of availability of levodopa from SINEMET was 99% relative to intravenous levodopa in the healthy elderly.
SINEMET CR50-200 200 0.70-0.75†† 140-150
SINEMET25-100 100 0.99††† 99

Dosage 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 III.

Table III: Guidelines for Initial Conversion from SINEMET (Carbidopa-Levodopa) 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 (Carbidopa-Levodopa)Total Daily Dose*Levodopa (mg) SINEMET CRSuggested 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.)

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