PRECAUTIONS General As with levodopa alone, periodic evaluations of hepatic, hematopoietic, cardiovascular, and renal function are recommended during extended concomitant therapy with Carbidopa Tablets and levodopa, or with Carbidopa Tablets and carbidopa-levodopa or any combination of these drugs. Impulse Control/Compulsive Behaviors Postmarketing reports suggest that patients treated with anti-Parkinson medications can experience intense urges to gamble, increased sexual urges, intense urges to spend money uncontrollably, binge eating, and other intense urges. Patients may be unable to control these urges while taking one or more of the medications that are used for the treatment of Parkinson’s disease and that increase central dopaminergic tone, including Carbidopa Tablets taken with levodopa and carbidopa. In some cases, although not all, these urges were reported to have stopped when the dose of anti-Parkinson medications was reduced or discontinued. Because patients may not recognize these behaviors as abnormal it is important for prescribers to specifically ask patients or their caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending or other urges while being treated with Carbidopa Tablets. Physicians should consider dose reduction or stopping Carbidopa Tablets or levodopa if a patient develops such urges while taking Carbidopa Tablets with carbidopa-levodopa. Hallucinations/Psychotic-Like Behavior Hallucinations and psychotic like behavior have been reported with dopaminergic medications. In general, hallucinations present shortly after the initiation of therapy and may be responsive to dose reduction in levodopa. Hallucinations may be accompanied by confusion and to a lesser extent sleep disorder (insomnia) and excessive dreaming. Carbidopa Tablets when taken with carbidopa-levodopa may have similar effects on thinking and behavior. This abnormal thinking and behavior may present with one or more symptoms, including paranoid ideation, delusions, hallucinations, confusion, psychotic-like behavior, disorientation, aggressive behavior, agitation, and delirium. Ordinarily, patients with a major psychotic disorder should not be treated with Carbidopa Tablets and carbidopa-levodopa, because of the risk of exacerbating psychosis. In addition, certain medications used to treat psychosis may exacerbate the symptoms of Parkinson’s disease and may decrease the effectiveness of Carbidopa Tablets. Dyskinesia Carbidopa Tablets may potentiate the dopaminergic side effects of levodopa and may cause or exacerbate preexisting dyskinesia Depression Patients treated with Carbidopa Tablets and carbidopa-levodopa should be observed carefully for the development of depression with concomitant suicidal tendencies Melanoma Epidemiological studies have shown that patients with Parkinson’s disease have a higher risk (2- to approximately 6-fold higher) of developing melanoma than the general population. Whether the observed increased risk was due to Parkinson’s disease or other factors, such as drugs used to treat Parkinson’s disease, is unclear. For the reasons stated above, patients and providers are advised to monitor for melanomas frequently and on a regular basis when using Carbidopa Tablets for Parkinson’s disease. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists). I nformation for Patients It is important that Carbidopa Tablets with levodopa be taken at regular intervals according to the schedule outlined by the health care provider. Caution patients not to change the prescribed dosage regimen and not to add any additional antiparkinson medications, including other carbidopa-levodopa preparations without first consulting a physician. Advise patients that sometimes a ‘wearing-off’ effect may occur at the end of the dosing interval. Tell patients to notify the prescriber if such response poses a problem to lifestyle. Patients should be advised that occasionally dark color (red, brown, or black) may appear in saliva, urine, or sweat after ingestion of Carbidopa Tablets and levodopa. Although the color appears to be clinically insignificant, garments may become discolored. The patient should be advised 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 in the body. The above factors may reduce the clinical effectiveness of the Carbidopa Tablets and levodopa therapy. Alert patients 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. Advise patients to exercise caution while driving or operating machinery and that if they have experience somnolence and/or sudden sleep onset, they must refrain from these activities. (See WARNINGS, Falling Asleep During Activities of Daily Living and Somnolence 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 Tablets and levodopa. 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 intense urges while taking Carbidopa Tablets and levodopa. Physicians should consider dose reduction or stopping Carbidopa Tablets and levodopa if a patient develops such urges while taking Carbidopa Tablets with carbidopa-levodopa (See PRECAUTIONS, Impulse Control/Compulsive Behaviors ). Laboratory Tests Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, SGOT (AST), SGPT (ALT), lactic dehydrogenase, and bilirubin. Abnormalities in blood urea nitrogen and positive Coombs test have also been reported. Commonly, levels of blood urea nitrogen, creatinine, and uric acid are lower during concomitant administration of carbidopa and levodopa than with levodopa alone. Levodopa and carbidopa-levodopa combination products may cause a false-positive reaction for urinary ketone bodies when a test tape is used for determination of ketonuria. This reaction will not be altered by boiling the urine specimen. False-negative tests may result with the use of glucose-oxidase methods of testing for glucosuria. Drug Interactions Caution should be exercised when the following drugs are administered concomitantly with Carbidopa Tablets given with levodopa or carbidopa-levodopa fixed dose combination products. Symptomatic postural hypotension has occurred when Carbidopa Tablets, given with levodopa or carbidopa-levodopa combination products, was added to the treatment of a patient receiving antihypertensive drugs. Therefore, when therapy with Carbidopa Tablets, given with or without levodopa or carbidopa-levodopa combination products, is started, dosage adjustment of the antihypertensive drug may be required. For patients receiving monoamine oxidase inhibitors (Type A or B), see CONTRAINDICATIONS . Concomitant therapy with selegiline or rasgiline and Carbidopa Tablets 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 Tablets and levodopa or carbidopa-levodopa combination products should be carefully observed for loss of therapeutic response. Carbidopa Tablets and iron salts or multi vitamins containing iron salts should be co administered 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. Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis There were no significant differences between treated and control rats with respect to mortality or neoplasia in a 96-week study of carbidopa at oral doses of 25, 45, or 135 mg/kg/day. Combinations of carbidopa and levodopa (10-20, 10-50, 10-100 mg/kg/day) were given orally to rats for 106 weeks. No effect on mortality or incidence and type of neoplasia was seen when compared to concurrent controls. Mutagenesis Mutagenicity studies have not been performed with either carbidopa or the combination of carbidopa and levodopa. Fertility Carbidopa had no effect on the mating performance, fertility, or survival of the young when administered orally to rats at doses of 30, 60, or 120 mg/kg/day. The highest dose caused a moderate decrease in body weight gain in males. The administration of carbidopa-levodopa at dose levels of 10-20, 10-50, or 10-100 mg/kg/day did not adversely affect the fertility of male or female rats, their reproductive performance, or the growth and survival of the young. Pregnancy Teratogenic Effects: Pregnancy Category C There are no adequate and well-controlled studies with Carbidopa Tablets 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. Carbidopa Tablets should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Carbidopa, at doses as high as 120 mg/kg/day, was without teratogenic effects in the mouse or rabbit. In the rabbit, but not in the mouse, carbidopa-levodopa produced visceral anomalies, similar to those seen with levodopa alone, at approximately 7 times the maximum recommended human dose. The teratogenic effect of levodopa in rabbits was unchanged by the concomitant administration of carbidopa. Nursing Mothers It is not known whether carbidopa is excreted in human milk. Because many drugs are excreted in human milk, and because of their potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the nursing woman. Pediatric Use Safety and effectiveness in pediatric patients have not been established, and use of the drug in patients below the age of 18 is not recommended. Geriatric Use Clinical studies of Carbidopa Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant disease and other drug therapy.