LODOSYN is indicated for use with SINEMET (Carbidopa-Levodopa) or with levodopa 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.

LODOSYN is for use with SINEMET (Carbidopa-Levodopa) in patients for whom the dosage of SINEMET (Carbidopa-Levodopa) provides less than adequate daily dosage (usually 70 mg daily) of carbidopa.

LODOSYN (carbidopa) is for use with levodopa in the occasional patient whose dosage requirement of carbidopa and levodopa necessitates separate titration of each entity.

LODOSYN is used with SINEMET (Carbidopa-Levodopa) or with levodopa to permit the administration of lower doses of levodopa with reduced nausea and vomiting, more rapid dosage titration, and with a somewhat smoother response. However, patients with markedly irregular ("on-off") responses to levodopa have not been shown to benefit from the addition of carbidopa.

Since carbidopa prevents the reversal of levodopa effects caused by pyridoxine, supplemental pyridoxine (vitamin B6), can be given to patients when they are receiving carbidopa and levodopa concomitantly or as SINEMET (Carbidopa-Levodopa).

Although the administration of LODOSYN (carbidopa) permits control of parkinsonism and Parkinson's disease with much lower doses of levodopa, there is no conclusive evidence at present that this is beneficial other than in reducing nausea and vomiting, permitting more rapid titration, and providing a somewhat smoother response to levodopa.

Certain patients who responded poorly to levodopa alone have improved when carbidopa and levodopa were given concurrently. This was most likely due to decreased peripheral decarboxylation of levodopa rather than to a primary effect of carbidopa on the peripheral nervous system. Carbidopa has not been shown to enhance the intrinsic efficacy of levodopa.

In considering whether to give LODOSYN with SINEMET (Carbidopa-Levodopa) or with levodopa to patients who have nausea and/or vomiting, the physician should be aware that, while many patients may be expected to improve, some may not. Since one cannot predict which patients are likely to improve, this can only be determined by a trial of therapy. It should be further noted that in controlled trials comparing carbidopa and levodopa with levodopa alone, about half the patients with nausea and/or vomiting on levodopa alone improved spontaneously despite being retained on the same dose of levodopa during the controlled portion of the trial.

Whether given with SINEMET (Carbidopa-Levodopa) or with levodopa, the optimal daily dosage of LODOSYN (carbidopa) must be determined by careful titration. Most patients respond to a 1:10 proportion of carbidopa and levodopa, provided the daily dosage of carbidopa is 70 mg or more a day. The maximum daily dosage of carbidopa should not exceed 200 mg, since clinical experience with larger dosages is limited. If the patient is taking SINEMET (Carbidopa-Levodopa), the amount of carbidopa in SINEMET (Carbidopa-Levodopa) should be considered when calculating the total amount of LODOSYN (carbidopa) to be administered each day.

Patients Receiving SINEMET (Carbidopa-Levodopa) Who Require Additional Carbidopa

Some patients taking SINEMET (Carbidopa-Levodopa) may not have adequate reduction in nausea and vomiting when the dosage of carbidopa is less than 70 mg a day, and the dosage of levodopa is less than 700 mg a day. When these patients are taking SINEMET 10-100** (Carbidopa-Levodopa), 25 mg of LODOSYN may be given with the first dose of SINEMET (Carbidopa-Levodopa) each day. Additional doses of 12.5 mg or 25 mg may be given during the day with each dose of SINEMET (Carbidopa-Levodopa). When patients are taking SINEMET 25-250*** (Carbidopa-Levodopa) or SINEMET 25-100^† (Carbidopa-Levodopa), 25 mg of LODOSYN may be given with any dose of SINEMET (Carbidopa-Levodopa) as required for optimum therapeutic response. The maximum daily dosage of carbidopa, given as LODOSYN and as SINEMET (Carbidopa-Levodopa), should not exceed 200 mg.

Patients Requiring Individual Titration of Carbidopa and Levodopa Dosage

Although SINEMET (Carbidopa-Levodopa) is the preferred method of carbidopa and levodopa administration, there may be an occasional patient who requires individually titrated doses of these two drugs. In these patients, LODOSYN (Carbidopa) should be initiated at a dosage of 25 mg three or four times a day. The two drugs should be given at the same time, starting with no more than one-fifth (20%) to one-fourth (25%) of the previous or recommended daily dosage of levodopa when given without LODOSYN (Carbidopa). In patients already receiving levodopa therapy, at least twelve hours should elapse between the last dose of levodopa and initiation of therapy with LODOSYN (Carbidopa) and levodopa. A convenient way to initiate therapy in these patients is in the morning following a night when the patient has not taken levodopa for at least twelve hours. Physicians who prescribe separate doses of LODOSYN (carbidopa) and levodopa should be thoroughly familiar with the directions for use of each drug.

Dosage Adjustment

Dosage of LODOSYN (carbidopa) may be adjusted by adding or omitting one-half or one tablet a day. Because both therapeutic and adverse responses occur more rapidly with combined therapy than when only levodopa is given, patients should be monitored closely during the dose adjustment period. Specifically, involuntary movements will occur more rapidly when LODOSYN (carbidopa) and levodopa are given concomitantly than when levodopa is given without LODOSYN (carbidopa) . The occurrence of involuntary movements may require dosage reduction. Blepharospasm may be a useful early sign of excess dosage in some patients.

Current evidence indicates other standard antiparkinsonian drugs may be continued while carbidopa and levodopa are being administered. However, the dosage of such other standard antiparkinsonian drugs may require adjustment.

Interruption of Therapy

Sporadic cases of a symptom complex resembling the Neuroleptic Malignant Syndrome (NMS) have been associated with dose reductions and withdrawal of SINEMET (Carbidopa-Levodopa) or SINEMET CR (Carbidopa-Levodopa) Sustained-Release. Patients should be observed carefully if abrupt reduction or discontinuation of SINEMET (Carbidopa-Levodopa) or SINEMET CR (Carbidopa-Levodopa) Sustained-Release is required, especially if the patient is receiving neuroleptics. (See WARNINGS.)

If general anesthesia is required, therapy may be continued as long as the patient is permitted to take fluids and medication by mouth. When therapy is interrupted temporarily, the patient should be observed for symptoms resembling NMS, and the usual daily dosage may be resumed as soon as the patient is able to take medication orally.

Tablets LODOSYN (carbidopa) , 25 mg, are orange, round, compressed tablets, that are scored and coded 511 on one side and LODOSYN (carbidopa) on the other.

They are supplied as follows:

NDC 0056-0511-68 bottles of 100.

Storage

Store at 25° C (77° F), excursions permitted to 15–30° C (59–86° F).

**SINEMET 10-100 (Carbidopa-Levodopa) contains 10 mg of carbidopa and 100 mg of levodopa.
***SINEMET 25-250 (Carbidopa-Levodopa) contains 25 mg of carbidopa and 250 mg of levodopa.
^†SINEMET 25-100 (Carbidopa-Levodopa) contains 25 mg of carbidopa and 100 mg of levodopa.

Manufactured by: MERCK & CO., INC. Whitehouse Station, NJ 08889, USA. Marketed by: Bristol Myers Squibb Co., Princeton, NJ 08543, USA. Revised September 2006. FDA Rev date: 12/18/2002

Last reviewed on RxList: 10/3/2008
This monograph has been modified to include the generic and brand name in many instances.