Efficacy of Caffeine, With and Without Biperiden, as a Maintenance Treatment for Cocaine Dependence

Inclusion Criteria: * diagnosis of cocaine dependence, according to DSM-IV-TR criteria * age between 18 and 60 years * current cocaine use, confirmed by a positive urine drug screen for cocaine the week prior to admission. * demonstrated capacity to grant informed consent and sign the pertinent informed consent form. * place of residence compatible with attendance at the center. * for women, willingness to use effective contraceptive measures during the study. Exclusion Criteria: * diagnosis of a severe medical disorder that could interfere with the study * presence of an organic pathology for which methylxanthines or biperidene administration is contraindicated * serum liver transaminase levels 3 times higher than normal values * pregnancy and breast-feeding * neuroleptic medication treatment in the past 6 weeks * current treatment, or anticipation that the patient may need to initiate treatment during the study, with drugs that may interact with study medication. * current diagnosis of a major mental disorder. * awareness of a situation that could prevent the patient's participation in the study (e.g. serving a sentence) * current participation in another research project.