INCREASED INCIDENCE OF LEVODOPA THERAPY FOLLOWING METOCLOPRAMIDE USE

Objective.-To determine whether there is an increase in use of antipar kinsonian therapy in older persons taking metoclopramide hydrochloride . Design.-Case-control study. Setting.-New Jersey Medicaid program. Pa tients.-Medicaid enrollees aged 65 years and older. Cases were patient s newly prescribed a levodopa-containing medication (n=1253); a second ary case group were patients newly prescribed an anticholinergic antip arkinsonian drug (n=2377). The control group consisted of 16 435 Medic aid enrollees older than 65 years who were not users of any antiparkin sonian therapy. Main Outcome Measures.-We used logistic regression to determine the odds ratio (OR) for the initiation of antiparkinsonian t herapy in patients using metoclopramide relative to nonusers, after ad justing for age, sex, race, nursing home residence, exposure to antips ychotic medication, and days hospitalized. Results.-Metoclopramide use rs were three times more likely to begin use of a levodopa-containing medication compared with nonusers (OR=3.09; 95% confidence interval [C I], 2.25 to 4.26). Risk increased with increasing daily metoclopramide dose: the OR was 1.19 (95% CI, 0.50 to 2.81) for more than 0 to 10 mg per day, 3.33 (95% CI, 1.98 to 5.58) for more than 10 to 20 mg per da y, and 5.25 (95% CI, 1.16 to 8.50) for more than 20 mg per day. The ef fect persisted after adjustment for demographic, health service utiliz ation, and medication use variables. The OR for initiation of antichol inergic antiparkinsonian drugs was also elevated in metoclopramide use rs. Conclusion.-Metoclopramide use confers an increased risk for the i nitiation of treatment generally reserved for the management of idiopa thic Parkinson's disease. Such polypharmacy may represent the misdiagn osis of Parkinson's disease in patients with drug-induced parkinsonian symptoms, which should be ruled out before starting dopaminergic ther apy for this condition.