LODOSYN (carbidopa) has no antiparkinsonian effect when given alone. It is indicated for use with carbidopa-levodopa or levodopa. LODOSYN (carbidopa) does not decrease adverse reactions due to central effects of levodopa.

When LODOSYN (carbidopa) is to be given to carbidopa-naive patients who are being treated with levodopa alone, the two drugs should be given at the same time. At least twelve hours should elapse between the last dose of levodopa and initiation of therapy with LODOSYN (carbidopa) and levodopa in combination. Start with no more than one-fifth (20%) to one-fourth (25%) of the previous daily dosage of levodopa when given without LODOSYN (carbidopa). See theDOSAGE AND ADMINISTRATIONsection before initiating therapy.

The addition of LODOSYN with levodopa or carbidopa-levodopa reduces the peripheral effects (nausea, vomiting) due to decarboxylation of levodopa; however, LODOSYN does not decrease the adverse reactions due to the central effects of levodopa. Because LODOSYN permits more levodopa to reach the brain and more dopamine to be formed, certain adverse central nervous system (CNS) effects, e.g., dyskinesias (involuntary movements), may occur at lower dosages and sooner with levodopa in combination with LODOSYN than with levodopa alone.

Falling Asleep During Activities of Daily Living and Somnolence    
Patients taking carbidopa-levodopa products alone or with other dopaminergic drugs have reported suddenly falling asleep without prior warning of sleepiness while engaged in activities of daily living (includes operation of motor vehicles). Some of these episodes resulted in automobile accidents. Although many of these patients reported somnolence while on dopaminergic medications, some did perceive that they had no warning signs, such as excessive drowsiness, and believed that they were alert immediately prior to the event. Some patients reported these events one year after the initiation of treatment.

Falling asleep while engaged in activities of daily living usually occurs in patients experiencing pre-existing somnolence, although some patients may not give such a history. For this reason, prescribers should continually reassess patients for drowsiness or sleepiness especially since some of the events occur after the start of treatment. Prescribers should be aware that patients may not acknowledge drowsiness or sleepiness until directly questioned about drowsiness or sleepiness during specific activities. Patients who have already experienced somnolence or an episode of sudden sleep onset should not participate in these activities during treatment with LODOSYN when taking it with other carbidopa-levodopa products.

Before initiating treatment with LODOSYN, advise patients about the potential to develop drowsiness and ask specifically about factors that may increase the risk for somnolence with LODOSYN such as the use of concomitant sedating medications and the presence of sleep disorders. Consider discontinuing LODOSYN in patients who report significant daytime sleepiness or episodes of falling asleep during activities that require active participation (e.g., conversations, eating, etc.). If treatment with LODOSYN continues, patients should be advised not to drive and to avoid other potentially dangerous activities that might result in harm if the patients become somnolent. There is insufficient information to establish that dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living.