Carbidopa and Levodopa

INDICATIONS AND USAGE Carbidopa and levodopa extended-release tablets, USP are indicated in the treatment of Parkinson's disease, post-encephalitic parkinsonism, and symptomatic parkinsonism that may follow carbon monoxide intoxication or manganese intoxication.

DOSAGE AND ADMINISTRATION Carbidopa and levodopa extended-release tablet contains carbidopa and levodopa in a 1:4 ratio as either the 50 mg/200 mg tablet or the 25 mg/100 mg tablet. The daily dosage of carbidopa and levodopa extended-release tablets 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. Carbidopa and levodopa extended-release tablets should not be chewed or crushed. Standard drugs for Parkinson’s disease, other than levodopa without a decarboxylase inhibitor, may be used concomitantly while carbidopa and levodopa extended-release tablet is being administered, although their dosage may have to be adjusted. Since carbidopa prevents the reversal of levodopa effects caused by pyridoxine, carbidopa and levodopa extended-release tablets can be given to patients receiving supplemental pyridoxine (vitamin B 6 ). Management of Vitamin B6 Levels Evaluate vitamin B6 levels prior to initiating carbidopa/levodopa therapies including carbidopa and levodopa extended-release tablet, periodically during treatment, and as clinically indicated (see WARNINGS, Vitamin B6 Deficiency and Seizures ) . If vitamin B6 levels are low, supplement to sufficient levels per standard of care. Patients may initiate and continue treatment with carbidopa and levodopa extended-release tablet while supplementing vitamin B6. Initial Dosage Patients currently treated with conventional carbidopa and 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 carbidopa and levodopa tablets and carbidopa and levodopa extended-release tablets 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 Carbidopa and Levodopa Extended-release Tablets, 50 mg/200 mg 200 0.70 to 0.75 † 140 to 150 Carbidopa and Levodopa Tablets, 25 mg/100 mg 100 0.99 †† 99 * 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 carbidopa and levodopa extended-release tablets was about 70% to 75% relative to intravenous levodopa or standard carbidopa and levodopa tablets in the elderly. †† The extent of availability of levodopa from carbidopa and levodopa tablets was 99% relative to intravenous levodopa in the healthy elderly. Dosage with carbidopa and levodopa extended-release tablets 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 carbidopa and levodopa extended-release tablet s ). The interval between doses of carbidopa and levodopa extended-release tablets should be 4 to 8 hours during the waking day. (see CLINICAL PHARMACOLOGY: Pharmacodynamics . ) A guideline for initiation of carbidopa and levodopa extended-release tablets is shown in Table 3. Table 3: Guidelines for Initial Conversion from Carbidopa and Levodopa Tablets to Carbidopa and Levodopa Extended-release Tablets Carbidopa and Levodopa Tablets Carbidopa and Levodopa Extended-release Tablets Total Daily Dose * Suggested Levodopa (mg) Dosage Regimen 300 to 400 200 mg b.i.d. 500 to 600 300 mg b.i.d. or 200 mg t.i.d. 700 to 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 to 1,000 A total of 1,000 mg in 3 or more divided doses (e.g., 400 mg a.m., 400 mg early p …

CONTRAINDICATIONS Nonselective monoamine oxidase (MAO) inhibitors are contraindicated for use with carbidopa and levodopa extended-release tablets. These inhibitors must be discontinued at least two weeks prior to initiating therapy with carbidopa and levodopa extended-release tablets. Carbidopa and levodopa extended-release tablets may be administered concomitantly with the manufacturer’s recommended dose of an MAO inhibitor with selectivity for MAO type B (e.g., selegiline hydrochloride) (see PRECAUTIONS, Drug Interactions ). Carbidopa and levodopa extended-release tablets are contraindicated in patients with known hypersensitivity to any component of this drug, and in patients with narrow-angle glaucoma.

ADVERSE REACTIONS In controlled clinical trials, patients predominantly with moderate to severe motor fluctuations while on carbidopa and levodopa were randomized to therapy with either carbidopa and levodopa or carbidopa and levodopa extended-release. The adverse experience frequency profile of carbidopa and levodopa extended-release did not differ substantially from that of carbidopa and levodopa, as shown in Table 1. Table 1: Clinical Adverse Experiences Occurring in 1% or Greater of Patients Adverse Experience Carbidopa and Levodopa Extended-release n = 491 % Carbidopa and 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 carbidopa and levodopa extended-release and 475 who received carbidopa and 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 carbidopa and levodopa extended-release, 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. The following adverse experiences have been reported in postmarketing experience with carbidopa and levodopa extended-release: Cardiovascular: Cardiac irregularities, syncope. Gastrointestinal: Taste alterations, dark saliva. Hypersensitivity: Angioedema, urticaria, pruritus, bullous lesions (including pemphigus-like reactions). Nervous System/Psychiatric: 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 carbidopa and levodopa extended-release are: Cardiovascular: Phlebitis. Gastrointestinal: Gastrointestinal bleeding, development of duodenal ulcer, sialorrhea, bruxism, hiccups, flatulence, burning sensation of tongue. Hematologic: Hemolytic and non-hemolytic 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 ta …

Drug Interactions Caution should be exercised when the following drugs are administered concomitantly with carbidopa and levodopa extended-release tablets. Symptomatic postural hypotension has occurred when carbidopa and levodopa preparations were added to the treatment of patients receiving some antihypertensive drugs. Therefore, when therapy with carbidopa and levodopa extended-release tablets is started, dosage adjustment of the antihypertensive drug may be required. For patients receiving MAO inhibitors (Type A or B), see CONTRAINDICATIONS . Concomitant therapy with selegiline and carbidopa and levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa and 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 and levodopa preparations. Dopamine D 2 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 carbidopa and levodopa extended-release tablets should be carefully observed for loss of therapeutic response. Use of carbidopa and levodopa extended-release tablets with dopamine-depleting agents (e.g., reserpine and tetrabenazine) or other drugs known to deplete monoamine stores is not recommended. Carbidopa and levodopa extended-release tablets and iron salts or multivitamins containing iron salts should be coadministered with caution. Iron salts can form chelates with levodopa and carbidopa and consequently reduce the bioavailability of carbidopa and levodopa. 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.

Special Populations Geriatric: A study in eight young healthy subjects (21 to 22 yr) and eight elderly healthy subjects (69 to 76 yr) showed that the absolute bioavailability of levodopa was similar between young and elderly subjects following oral administration of levodopa and carbidopa. However, the systemic exposure (AUC) of levodopa was increased by 55% in elderly subjects compared to young subjects. Based on another study in forty patients with Parkinson’s disease, there was a correlation between age of patients and the increase of AUC of levodopa following administration of levodopa and an inhibitor of peripheral dopa decarboxylase. AUC of levodopa was increased by 28% in elderly patients (≥ 65 yr) compared to young patients (< 65 yr). Additionally, mean value of C max for levodopa was increased by 24% in elderly patients (≥ 65 yr) compared to young patients (< 65 yr) (see PRECAUTIONS , Geriatric Use ). The AUC of carbidopa was increased in elderly subjects (n=10, 65 to 76 yr) by 29% compared to young subjects (n=24, 23 to 64 yr) following IV administration of 50 mg levodopa with carbidopa (50 mg). This increase is not considered a clinically significant impact.

Mechanism of Action Parkinson’s disease is a progressive, neurodegenerative disorder of the extrapyramidal nervous system affecting the mobility and control of the skeletal muscular system. Its characteristic features include resting tremor, rigidity, and bradykinetic movements. Symptomatic treatments, such as levodopa therapies, may permit the patient better mobility. Current evidence indicates that symptoms of Parkinson’s disease are related to depletion of dopamine in the corpus striatum. Administration of dopamine is ineffective in the treatment of Parkinson’s disease apparently because it does not cross the blood-brain barrier. However, levodopa, the metabolic precursor of dopamine, does cross the blood-brain barrier, and presumably is converted to dopamine in the brain. This is thought to be the mechanism whereby levodopa relieves symptoms of Parkinson’s disease.

DESCRIPTION Carbidopa and levodopa extended-release tablets, USP are an extended-release combination of carbidopa and levodopa for the treatment of Parkinson’s disease and syndrome. Carbidopa, USP , an inhibitor of aromatic amino acid decarboxylation, is a white to creamy white, odorless or practically odorless powder, freely soluble in 3N hydrochloric acid, slightly soluble in water and in methanol, practically insoluble in alcohol, in acetone, in chloroform and in ether, with a molecular weight of 244.24. It is designated chemically as (-)-L-α­hydrazino-α-methyl-β-(3,4-dihydroxybenzene) propanoic acid monohydrate. Its empirical formula is C 10 H 14 N 2 O 4 •H 2 O, and its structural formula is: Tablet content is expressed in terms of anhydrous carbidopa, which has a molecular weight of 226.24. Levodopa, USP, an aromatic amino acid, is a white to off-white, odorless , crystalline powder, slightly soluble in water, freely soluble in 3N hydrochloric acid and insoluble in alcohol with a molecular weight of 197.19. It is designated chemically as (-)-L-α-amino-β-(3,4-dihydroxybenzene) propanoic acid. Its empirical formula is C 9 H 11 NO 4 , and its structural formula is: Carbidopa and levodopa extended-release tablets, USP are supplied as extended-release tablets containing either 25 mg of carbidopa and 100 mg of levodopa, or 50 mg of carbidopa and 200 mg of levodopa. Inactive ingredients are hydroxypropyl cellulose, magnesium stearate, and hypromellose. Carbidopa and levodopa extended-release tablets USP, 25 mg/100 mg and carbidopa and levodopa extended-release tablets USP, 50 mg/200 mg also contain FD&C Blue #2 Aluminium Lake and FD&C Red #40 Aluminium Lake. The 25 mg/100 mg tablet is supplied as an oval shaped mottled tablet that is dappled-purple in color and is debossed with “L519” on one side and plain on the other. The 50 mg/200 mg tablet is supplied as an oval shaped mottled tablet that is dappled-purple in color and is debossed with “L520” on one side and plain on the other. Carbidopa and levodopa extended-release tablets, USP are polymeric-based drug delivery system that controls the release of carbidopa and levodopa as it slowly erodes. Carbidopa and levodopa extended-release tablet 25 mg/100 mg is available to facilitate titration when 100 mg steps are required. FDA approved dissolution specifications differs from the USP dissolution specifications. Structure-Carbidopa Structure-Levodopa

OVERDOSAGE Management of acute overdosage with carbidopa and levodopa extended-release tablets is the same as with levodopa. Pyridoxine is not effective in reversing the actions of carbidopa and levodopa extended-release tablets. 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 carbidopa and levodopa extended-release tablets 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 1,500 mg/kg to 2,000 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 3,360 mg/kg.

HOW SUPPLIED Carbidopa and levodopa extended-release tablets USP, 25 mg/100 mg containing 25 mg of carbidopa and 100 mg of levodopa, are dappled-purple in color, oval shaped mottled tablets debossed with “L519” on one side and plain on other side. They are supplied as follows: NDC 46708-332-30 Bottle of 30 tablets NDC 46708-332-31 Bottle of 100 tablets NDC 46708-332-91 Bottle of 1000 tablets Carbidopa and levodopa extended-release tablets USP, 50 mg/200 mg containing 50 mg of carbidopa and 200 mg of levodopa, are dappled-purple in color, oval shaped mottled tablets debossed with “L520” on one side and plain on other side. They are supplied as follows: NDC 46708-333-30 Bottle of 30 tablets NDC 46708-333-31 Bottle of 100 tablets NDC 46708-333-91 Bottle of 1000 tablets Storage and Handling Store at 25°C (77°F), excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Store in a tightly closed container, protected from light and moisture. Dispense in a tightly closed, light-resistant container. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. Manufactured by: Alembic Pharmaceuticals Limited (Formulation Division), Village Panelav, P. O. Tajpura, Near Baska, Taluka-Halol, Panchmahal, Gujarat, India. Revised: 01/2018