SINEMET CR (Page 3 of 5)

Drug Interactions

Caution should be exercised when the following drugs are administered concomitantly with SINEMET CR (Carbidopa-Levodopa) Sustained-Release.

Symptomatic postural hypotension has occurred when carbidopa-levodopa preparations were added to the treatment of patients receiving some antihypertensive drugs. Therefore, when therapy with SINEMET CR is started, dosage adjustment of the antihypertensive drug may be required.

For patients receiving monoamine oxidase (MAO) inhibitors (Type A or B), see CONTRAINDICATIONS. Concomitant therapy with selegiline and carbidopa-levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa-levodopa alone (see CONTRAINDICATIONS).

There have been rare reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa-levodopa preparations.

Dopamine D2 receptor antagonists (e.g., phenothiazines, butyrophenones, risperidone) and isoniazid may reduce the therapeutic effects of levodopa. In addition, the beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with SINEMET CR should be carefully observed for loss of therapeutic response.

Iron salts may reduce the bioavailability of levodopa and carbidopa. The clinical relevance is unclear.

Although metoclopramide may increase the bioavailability of levodopa by increasing gastric emptying, metoclopramide may also adversely affect disease control by its dopamine receptor antagonistic properties.

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 (equivalent to 8 SINEMET CR tablets).

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 (equivalent to 8 SINEMET CR tablets).

Pregnancy

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 placental barrier, enters the fetus, and is metabolized. Carbidopa concentrations in fetal tissue appeared to be minimal. Use of SINEMET CR in women of childbearing potential requires that the anticipated benefits of the drug be weighed against possible hazards to mother and child.

Nursing Mothers

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 CR is administered to a nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Use of the drug in patients below the age of 18 is not recommended.

ADVERSE REACTIONS

In controlled clinical trials, patients predominantly with moderate to severe motor fluctuations while on SINEMET (Carbidopa-Levodopa) were randomized to therapy with either SINEMET (Carbidopa-Levodopa) or SINEMET CR. The adverse experience frequency profile of SINEMET CR did not differ substantially from that of SINEMET (Carbidopa-Levodopa), as shown in Table I.

Table I: Clinical Adverse Experiences Occurring in 1% or Greater of Patients
Adverse Experience SINEMET CRn = 491% SINEMET(Carbidopa-Levodopa)n = 524%
Dyskinesia 16.5 12.2
Nausea 5.5 5.7
Hallucinations 3.9 3.2
Confusion 3.7 2.3
Dizziness 2.9 2.3
Depression 2.2 1.3
Urinary tract infection 2.2 2.3
Headache 2.0 1.9
Dream abnormalities 1.8 0.8
Dystonia 1.8 0.8
Vomiting 1.8 1.9
Upper respiratory infection 1.8 1.0
Dyspnea 1.6 0.4
‘On-Off’ phenomena 1.6 1.1
Back pain 1.6 0.6
Dry mouth 1.4 1.1
Anorexia 1.2 1.1
Diarrhea 1.2 0.6
Insomnia 1.2 1.0
Orthostatic hypotension 1.0 1.1
Shoulder pain 1.0 0.6
Chest pain 1.0 0.8
Muscle cramps 0.8 1.0
Paresthesia 0.8 1.1
Urinary frequency 0.8 1.1
Dyspepsia 0.6 1.1
Constipation 0.2 1.5

Abnormal laboratory findings occurring at a frequency of 1% or greater in approximately 443 patients who received SINEMET CR and 475 who received SINEMET (Carbidopa-Levodopa) during controlled clinical trials included: decreased hemoglobin and hematocrit; elevated serum glucose; white blood cells, bacteria and blood in the urine.

The adverse experiences observed in patients in uncontrolled studies were similar to those seen in controlled clinical studies.

Other adverse experiences reported overall in clinical trials in 748 patients treated with SINEMET CR, listed by body system in order of decreasing frequency, include:

Body as a Whole: Asthenia, fatigue, abdominal pain, orthostatic effects.

Cardiovascular: Palpitation, hypertension, hypotension, myocardial infarction.

Gastrointestinal: Gastrointestinal pain, dysphagia, heartburn.

Metabolic: Weight loss.

Musculoskeletal: Leg pain.

Nervous System/Psychiatric: Chorea, somnolence, falling, anxiety, disorientation, decreased mental acuity, gait abnormalities, extrapyramidal disorder, agitation, nervousness, sleep disorders, memory impairment.

Respiratory: Cough, pharyngeal pain, common cold.

Skin: Rash.

Special Senses: Blurred vision.

Urogenital: Urinary incontinence.

Laboratory Tests: Decreased white blood cell count and serum potassium; increased BUN, serum creatinine and serum LDH; protein and glucose in the urine.

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