Professional Information — Carbidopa And Levodopa L200

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 25 mg/100 mg tablet or the 50 mg/200 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 B₆).

Management of Vitamin B₆ Levels

Evaluate vitamin B₆ levels prior to initiating carbidopa/levodopa therapies including carbidopa and levodopa extended-release tablets, 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 tablets while supplementing 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 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 ^*

^* 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 tablets). 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 tablet is shown in Table 3.
Table 3: Guidelines for Initial Conversion from Carbidopa and Levodopa Tablets to Carbidopa and Levodopa Extended-Release Tablets 

* For dosing ranges not shown in the table see DOSAGE AND ADMINISTRATION, Initial Dosage — Patients currently treated with conventional carbidopa levodopa preparations.

Patients currently treated with levodopa without a decarboxylase inhibitor: Levodopa must be discontinued at least twelve hours before therapy with carbidopa and levodopa extended-release tablet is started. Carbidopa and levodopa extended-release tablets 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 carbidopa and levodopa extended-release tablet 50 mg/200 mg b.i.d.

Patients not receiving levodopa: In patients with mild to moderate disease, the initial recommended dose is 1 tablet of carbidopa and levodopa extended-release tablet 50 mg/200 mg b.i.d. Initial dosage should not be given at intervals of less than 6 hours.

  Titration with Carbidopa and Levodopa Extended-Release Tablets 

Following 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 carbidopa and levodopa extended-release tablets 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 carbidopa and levodopa extended-release tablets (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 carbidopa and levodopa extended-release tablets 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.

  Maintenance 

Because Parkinson’s disease is progressive, periodic clinical evaluations are recommended; adjustment of the dosage regimen of carbidopa and levodopa extended-release tablets may be required.

  Addition of Other Antiparkinson Medications 

Anticholinergic agents, dopamine agonists, and amantadine can be given with carbidopa and levodopa extended-release tablets. Dosage adjustment of carbidopa and levodopa extended-release tablets may be necessary when these agents are added.

A dose of carbidopa levodopa immediate release 25 mg/100 mg or 10 mg/100 mg (one half or a whole tablet) can be added to the dosage regimen of carbidopa and levodopa extended-release tablets in selected patients with advanced disease who need additional immediate-release levodopa for a brief time during daytime hours.  Interruption of Therapy 

Sporadic cases of hyperpyrexia and confusion have been associated with dose reductions and withdrawal of carbidopa and levodopa tablets or carbidopa and levodopa extended-release tablets. 

Patients should be observed carefully if abrupt reduction or discontinuation of carbidopa and levodopa extended-release tablet is required, especially if the patient is receiving neuroleptics. (See WARNINGS.) 

If general anesthesia is required, carbidopa and levodopa extended-release tablets 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.

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 HCl) (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 tablets were randomized to therapy with either carbidopa and levodopa tablets or carbidopa and levodopa extended-release tablets. The adverse experience frequency profile of carbidopa and levodopa extended-release tablets 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 

Abnormal laboratory findings occurring at a frequency of 1% or greater in approximately 443 patients who received carbidopa and levodopa extended-release tablets and 475 who received carbidopa and levodopa tablets 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 tablets, 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 tablets:

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, seizures (including convulsions).

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 tablets 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-Schönlein purpura.

Metabolic 

Weight gain, edema.

Nervous System/Psychiatric 

Ataxia, depression with suicidal tendencies, dementia, euphoria, 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, 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, vitamin B₆ levels.

To report SUSPECTED ADVERSE REACTIONS, contact Alembic Pharmaceuticals Limited at 1-866-210-9797 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

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 levodopa preparations were added to the treatment of patients receiving some antihypertensive drugs. Therefore, when therapy with carbidopa and levodopa extended-release tablet 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 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 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.

Overdosage

Management of acute overdosage with carbidopa and levodopa extended-release tablet 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 1500 to 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.

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 C₁₀H₁₄N₂O₄•H₂O, 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 C₉H₁₁NO₄, 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, hypromellose and magnesium stearate. 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.

Clinical Pharmacology

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.

Pharmacodynamics
When levodopa is administered orally, it is rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system. For this reason, large doses of levodopa are required for adequate therapeutic effect, and these may often be accompanied by nausea and other adverse reactions, some of which are attributable to dopamine formed in extracerebral tissues.

Since levodopa competes with certain amino acids for transport across the gut wall, the absorption of levodopa may be impaired in some patients on a high protein diet.

Carbidopa inhibits decarboxylation of peripheral levodopa. It does not cross the blood-brain barrier and does not affect the metabolism of levodopa within the central nervous system.

Since its decarboxylase inhibiting activity is limited to extracerebral tissues, administration of carbidopa with levodopa makes more levodopa available for transport to the brain.

Patients treated with levodopa therapy for Parkinson’s disease may develop motor fluctuations characterized by end-of-dose failure, peak dose dyskinesia, and akinesia. The advanced form of motor fluctuations (‘on-off’ phenomenon) is characterized by unpredictable swings from mobility to immobility. Although the causes of the motor fluctuations are not completely understood, in some patients they may be attenuated by treatment regimens that produce steady plasma levels of levodopa.

Carbidopa and levodopa extended-release tablets contain either 25 mg of carbidopa and 100 mg of levodopa, or 50 mg of carbidopa and 200 mg of levodopa in a extended-release dosage form designed to release these ingredients over a 4- to 6-hour period. With carbidopa and levodopa extended-release tablets there is less variation in plasma levodopa levels than with carbidopa and levodopa tablets, the conventional formulation. However, carbidopa and levodopa extended-release tablets are less systemically bioavailable than carbidopa and levodopa tablets and may require increased daily doses to achieve the same level of symptomatic relief as provided by carbidopa and levodopa tablets.

In clinical trials, patients with moderate to severe motor fluctuations who received carbidopa and levodopa extended-release tablets did not experience quantitatively significant reductions in ‘off’ time when compared to carbidopa and levodopa tablets. However, global ratings of improvement as assessed by both patient and physician were better during therapy with carbidopa and levodopa extended-release tablets than with carbidopa and levodopa tablets. In patients without motor fluctuations, carbidopa and levodopa extended-release tablets, under controlled conditions, provided the same therapeutic benefit with less frequent dosing when compared to carbidopa and levodopa tablets.

Pharmacokinetics
Carbidopa reduces the amount of levodopa required to produce a given response by about 75% and, when administered with levodopa, increases both plasma levels and the plasma half-life of levodopa, and decreases plasma and urinary dopamine and homovanillic acid.

Elimination half-life of levodopa in the presence of carbidopa is about 1.5 hours. Following carbidopa and levodopa extended-release tablets, the apparent half-life of levodopa may be prolonged because of continuous absorption.

In healthy elderly subjects (56 to 67 years old) the mean time-to-peak concentration of levodopa after a single dose of carbidopa and levodopa extended-release tablets 50 mg/200 mg was about 2 hours as compared to 0.5 hours after standard carbidopa and levodopa tablets. The maximum concentration of levodopa after a single dose of carbidopa and levodopa extended-release tablets was about 35% of the standard carbidopa and levodopa tablets (1151 vs. 3256 ng/mL). 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 absolute bioavailability of levodopa from carbidopa and levodopa extended-release tablets (relative to I.V.) in young subjects was shown to be only about 44%. The extent of availability and the peak concentrations of levodopa were comparable in the elderly after a single dose and at steady state after t.i.d. administration of carbidopa and levodopa extended-release tablets 50 mg/200 mg. In elderly subjects, the average trough levels of levodopa at steady state after the CR tablet were about 2 fold higher than after the standard carbidopa and levodopa tablets (163 vs. 74 ng/mL).

In these studies, using similar total daily doses of levodopa, plasma levodopa concentrations with carbidopa and levodopa extended-release tablets fluctuated in a narrower range than with carbidopa and levodopa tablets. Because the bioavailability of levodopa from carbidopa and levodopa extended-release tablets relative to carbidopa and levodopa tablets is approximately 70 to 75%, the daily dosage of levodopa necessary to produce a given clinical response with the sustained-release formulation will usually be higher.

The extent of availability and peak concentrations of levodopa after a single dose of carbidopa and levodopa extended-release tablets 50 mg/200 mg increased by about 50% and 25%, respectively, when administered with food.

At steady state, the bioavailability of carbidopa from carbidopa and levodopa tablet is approximately 99% relative to the concomitant administration of carbidopa and levodopa. At steady state, carbidopa bioavailability from carbidopa and levodopa extended-release tablets 50 mg/200 mg is approximately 58% relative to that from carbidopa and levodopa tablets.

Pyridoxine hydrochloride (vitamin B₆), in oral doses of 10 mg to 25 mg, may reverse the effects of levodopa by increasing the rate of aromatic amino acid decarboxylation. Carbidopa inhibits this action of pyridoxine.

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.

How Supplied / Storage and Handling

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 62332-332-30                Bottle of 30 tablets

NDC 62332-332-31                Bottle of 100 tablets

NDC 62332-332-91                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 62332-333-30                Bottle of 30 tablets

NDC 62332-333-31                Bottle of 100 tablets

NDC 62332-333-91                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.

Manufactured by:

Alembic Pharmaceuticals Limited

(Formulation Division),

Panelav 389350, Gujarat, India 

Manufactured for:

Alembic Pharmaceuticals, Inc.

Bedminster, NJ 07921, USA 

Revised: 04/2026

Patient Counseling Information

The patient should be informed that carbidopa and levodopa extended-release tablet is an extended-release formulation of carbidopa and levodopa which releases these ingredients over a 4- to 6-hour period. It is important that carbidopa and levodopa extended-release tablets be taken at regular intervals according to the schedule outlined by the physician. The patient should be cautioned not to change the prescribed dosage regimen and not to add any additional antiparkinson medications, including other carbidopa and levodopa preparations, without first consulting the physician.

If abnormal involuntary movements appear or get worse during treatment with carbidopa and levodopa extended-release tablets, the physician should be notified, as dosage adjustment may be necessary.

Patients should be advised that sometimes the onset of effect of the first morning dose of carbidopa and levodopa extended-release tablets may be delayed for up to 1 hour compared with the response usually obtained from the first morning dose of carbidopa and levodopa tablets. The physician should be notified if such delayed responses pose a problem in treatment.

Patients should be advised that, occasionally, dark color (red, brown, or black) may appear in saliva, urine, or sweat after ingestion of carbidopa and levodopa extended-release tablets. Although the color appears to be clinically insignificant, garments may become discolored.

The patient should be informed that a change in diet to foods that are high in protein may delay the absorption of levodopa and may reduce the amount taken up in the circulation. Excessive acidity also delays stomach emptying, thus delaying the absorption of levodopa. Iron salts (such as in multivitamin tablets) may also reduce the amount of levodopa available to the body. The above factors may reduce the clinical effectiveness of the levodopa or carbidopa levodopa therapy.

Patients must be advised that the whole or half tablet should be swallowed without chewing or crushing.

Patients should be alerted to the possibility of sudden onset of sleep during daily activities, in some cases without awareness or warning signs, when they are taking dopaminergic agents, including levodopa. Patients should be advised to exercise caution while driving or operating machinery and that if they have experienced somnolence and/or sudden sleep onset, they must refrain from these activities. (See WARNINGS, Falling Asleep During Activities of Daily Living and Somnolence.)

There have been reports of patients experiencing intense urges to gamble, increased sexual urges, and other intense urges, and the inability to control these urges while taking one or more of the medications that increase central dopaminergic tone and that are generally used for the treatment of Parkinson’s disease, including carbidopa and levodopa extended-release tablets. Although it is not proven that the medications caused these events, these urges were reported to have stopped in some cases when the dose was reduced or the medication was stopped. Prescribers should ask patients about the development of new or increased gambling urges, sexual urges or other urges while being treated with carbidopa and levodopa extended-release tablets. Patients should inform their physician if they experience new or increased gambling urges, increased sexual urges, or other intense urges while taking carbidopa and levodopa extended-release tablets. Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking carbidopa and levodopa extended-release tablets (see PRECAUTIONS, Impulse Control / Compulsive  Behaviors).

Inform patients that vitamin B₆ deficiency may develop during treatment with carbidopa/levodopa therapies, including carbidopa and levodopa extended-release tablets. Tell patients to inform their healthcare provider if they develop symptoms such as depression, confusion, cheilosis, glossitis, dermatitis, anemia, neuropathy, and/or seizures (see WARNINGS, Vitamin B₆ Deficiency and Seizures).