 2. To determine the safety of rivastigmine and HupA in cocaine-dependent participants who receive cocaine in a laboratory setting. Hypothesis 2A. Relative to placebo-treated participants, treatment with rivastigmine or HupA will not increase the adverse events produced by cocaine. Hypothesis 2B. Relative to placebo-treated participants, treatment with rivastigmine or HupA will reduce cocaine-induced increases in heart rate and blood pressure. 