All groups received a single dose of albendazole ivermectin between 12 and 36 months generic zithromax over the counter Two moderate size and three small retrospective cohort studies and one case control study found an association between CYP2D6 reduced metabolizers and decreased RFS or DFS, while three moderate size retrospective cohort studies and one randomized trial retrospectively analysis of both treatment and control groups did find no association or the exact opposite results a decreased recurrence risk among CYP2D6 reduced metabolizers