Carbidopa 25 MG / Levodopa 100 MG Extended Release Oral Tablet

WARNINGS

When patients are receiving levodopa without a decarboxylase inhibitor, levodopa must be discontinued at least twelve hours before carbidopa and levodopa extended-release tablets are started.

In order to reduce adverse reactions, it is necessary to individualize therapy.

Carbidopa and levodopa extended-release tablets 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 CNS effects, e.g., dyskinesias, will occur at lower dosages and sooner during therapy with carbidopa and levodopa extended-release tablets than with levodopa alone.

Patients receiving carbidopa and levodopa extended-release tablets may develop increased dyskinesias compared to carbidopa and levodopa tablets.

Dyskinesias are a common side effect of carbidopa and levodopa treatment.

The occurrence of dyskinesias may require dosage reduction.

As with levodopa, carbidopa and levodopa extended-release tablets may cause mental disturbances.

These reactions are thought to be due to increased brain dopamine following administration of levodopa.

All patients should be observed carefully for the development of depression with concomitant suicidal tendencies.

Patients with past or current psychoses should be treated with caution.

Carbidopa and levodopa extended-release tablets 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 carbidopa and levodopa extended-release tablets 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 carbidopa and levodopa extended-release tablets may increase the possibility of upper gastrointestinal hemorrhage in patients with a history of peptic ulcer.

Neuroleptic Malignant Syndrome (NMS): Sporadic cases of a symptom complex resembling NMS have been reported in association with dose reductions or withdrawal of carbidopa and levodopa tablets and carbidopa and levodopa extended-release tablets.

Therefore, patients should be observed carefully when the dosage of carbidopa and levodopa extended-release tablets 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.

DRUG INTERACTIONS

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 monoamine oxidase (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.

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.

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 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 are extended-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 molecular 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 226.3.

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 molecular formula is C 9 H 11 NO 4 and its structural formula is: Carbidopa and levodopa extended-release tablets are supplied as extended-release tablets containing either 50 mg of carbidopa USP and 200 mg of levodopa USP, or 25 mg of carbidopa USP and 100 mg of levodopa USP.

Inactive ingredients: microcrystalline cellulose, colloidal silicon dioxide, hypromellose, hydroxypropyl cellulose, magnesium stearate, red ferric oxide and D&C Yellow 10 Aluminum lake.

The 50 mg/200 mg tablet is supplied as an oval, scored, biconvex, compressed tablet debossed “457” on one side and scored on other side that is buff colored with mottled appearance.

The 25 mg/100 mg tablet is supplied as an oval, biconvex, compressed tablet debossed “461” on one side and plain on other side that is buff colored with mottled appearance.

Carbidopa and levodopa extended-release tablet is a 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.

carbidopa-structure levodopa-structure

HOW SUPPLIED

Carbidopa and levodopa extended-release tablets 50 mg/200 mg containing 50 mg of carbidopa and 200 mg of levodopa, are buff colored, oval, biconvex uncoated tablets debossed “457” on one side and scored on other side, with mottled appearance.

They are supplied as follows: NDC 62756-457-83 bottles of 30 NDC 62756-457-88 bottles of 100 (CRC) NDC 62756-457-08 bottles of 100 (NCRC) NDC 62756-457-18 bottles of 1000 Carbidopa and levodopa extended-release tablets 25 mg/100 mg containing 25 mg carbidopa and 100 mg of levodopa, are buff colored, oval, biconvex, uncoated tablets debossed “461” on one side and plain on other side, with mottled appearance.

They are supplied as follows: NDC 62756-461-83 bottles of 30 NDC 62756-461-88 bottles of 100 (CRC) NDC 62756-461-08 bottles of 100 (NCRC) NDC 62756-461-18 bottles of 1000 Storage Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F 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.

INDICATIONS AND USAGE

Carbidopa and levodopa extended-release tablets are indicated in the treatment of the symptoms of idiopathic Parkinson’s disease (paralysis agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication and/or manganese intoxication.

PEDIATRIC USE

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.

PREGNANCY

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 carbidopa and levodopa tablets.

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.

Carbidopa and levodopa tablets 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 carbidopa and levodopa extended-release tablets in women of childbearing potential requires that the anticipated benefits of the drug be weighed against possible hazards to mother and child.

NUSRING MOTHERS

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 carbidopa and levodopa extended-release tablets are administered to a nursing woman.

INFORMATION FOR PATIENTS

Information for Patients 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 and 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 PRECAUTIONS, General .) 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.

NOTE: The suggested advice to patients being treated with carbidopa and levodopa extended-release tablets is intended to aid in the safe and effective use of this medication.

It is not a disclosure of all possible adverse or intended effects.

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 ).

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 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.

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 0.7 to 0.75 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.

140 to 150 Carbidopa and levodopa tablets 25 mg/100 mg 100 0.99 The extent of availability of levodopa from carbidopa and levodopa tablets was 99% relative to intravenous levodopa in the healthy elderly.

99 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 , 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 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 For dosing ranges not shown in the table see , Initial Dosage-Patients currently treated with conventional carbidopa and levodopa preparations.

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 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 carbidopa and levodopa extended-release tablets 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 tablets 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 tablets 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 and levodopa tablets 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 a symptom complex resembling Neuroleptic Malignant Syndrome (NMS) 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 tablets 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.