Detailed Drug Information:

DRUG CLASS AND MECHANISM: Levodopa-carbidopa is a combination oftwo drugs, levodopa and carbidopa. Levodopa-carbidopa is used in thetreatment of Parkinson's disease. Parkinson's disease is believed to berelated to low levels of dopamine in certain parts of the brain. Whenlevodopa is taken orally, it crosses through the "blood-brainbarrier." Once it crosses, it is converted to dopamine. The resultingincrease in brain dopamine concentrations is believed to improve nerveconduction and assist the movement disorders in Parkinson disease.Carbidopa does not cross the blood-brain barrier. Carbidopa is added tothe levodopa to prevent the breakdown of levodopa before it crosses intothe brain. The addition of carbidopa allows lower doses of levodopa to beused. This reduces the risk of side effects from levodopa such as nauseaand vomiting. This combination medicine was approved by the FDA in 1988.

GENERIC EQUIVALNET AVAILABLE: yes

PREPARATIONS: Oval tablets (doses stated are forlevodopa/carbidopa): 100mg/10mg, 200mg/20mg, 200mg/25mg, 250mg/25mg, and asustained-release preparation (Sinemet CR) containing 200mg/50mg.

STORAGE: Tablets should be kept at room temperature, 15-30°C(59-86°F).

PRESCRIBED FOR: Levodopa-carbidopa is indicated for themanagement of Parkinson's disease.

DOSING: Levodopa-carbidopa is taken several times per day. Itmay be administered with food to reduce the likelihood of nausea. However,a high-protein diet may reduce its absorption.

DRUG INTERACTIONS: The use of amantadine (Symmetrel),benztropine (Cogentin), procyclidine (Kemadrin), or trihexyphenidyl(Artane) with levodopa-carbidopa can enhance the anti-Parkinson's effectsof levodopa. Droperidol, haloperidol (Haldol), loxapine (Loxitane),metoclopramide (Reglan), phenothiazines such as prochlorperazine(Thorazine); thioxanthenes as thiothixene (Navane) inhibit dopamine in thebrain. These drugs, therefore, can worsen Parkinson's disease and reversethe beneficial effects of levodopa. Methyldopa (Aldomet) and reserpinealso can interfere with the beneficial actions of levodopa-carbidopa andcan increase the risk of side effects.

Phenytoin (Dilantin) can increases the break-down of levodopa-carbidopa,reducing its effectiveness.

Use of levodopa-carbidopa with monoamine oxidase inhibitors (MAOI's)antidepressants, for example, isocarboxazid (Marplan), phenelzine(Nardil), tranylcypromine (Parnate), and procarbazine (Matulane), canresult in severe and dangerous elevations in blood pressure. MAOI's shouldbe stopped 2-4 weeks before starting levodopa-carbidopa therapy.

The side effects associated with levodopa, including dizziness uponrising, confusion, movement disorders, nausea, and hallucinations, all canbe increased by selegiline (Eldepryl).

PREGNANCY: Although there are no human studies that haveexamined the effects of levodopa-carbidopa on the fetus, animal studieshave shown adverse effects. Therefore, in prescribing levodopa-carbidopafor a pregnant woman, the physician must weigh the potential risks to thefetus against the potential benefits to the mother.

NURSING MOTHERS: Levodopa is distributed into breast milk. Italso may inhibit production of milk. It is generally recommended thatlevodopa-carbidopa should not be given to women who are breast-feeding.

SIDE EFFECTS: Most patients receiving levodopa-carbidopaexperience side effects, but these are usually reversible. Occasionalinvoluntary movements are the most common of the serious side effects oflevodopa-carbidopa therapy. These may include chewing, gnawing, twisting,tongue or mouth movements, head bobbing, or movements of the feet, hands,or shoulder. These may respond to a reduction in the dose. Muscletwitching, dizziness, muscle jerks during sleep, and hand tremor also may occur. Various psychiatric disturbances may occur duringlevodopa-carbidopa therapy. Such disturbances include memory loss,anxiety, nervousness, agitation, restlessness, confusion, inability tosleep, nightmares, daytime tiredness, mental depression or euphoria.

Gastrointestinal side effects are common in patients receivinglevodopa-carbidopa. Nausea, vomiting, loss of appetite, and weight lossmay occur. Patients may experience dizziness upon standing up, associatedwith a drop in blood pressure. Fortunately, the body develops tolerance tothis side effect within a few months.

Infrequently, patients may develop a drop in white blood cell countduring levodopa-carbidopa therapy. This is a cause to temporarily, if notpermanently, stop treatment.