Metformin is one of the most commonly prescribed drugs worldwide for the treatment of Type 2 Diabetes. It has been currently used for the treatment of: polycystic ovary syndrome, gestational diabetes, metabolic syndrome and obesity. In patients with polycystic ovary syndrome (PCOS) the adverse side effects are a frequent cause for treatment discontinuation. In every day medical practice lower doses of Metformin are administered searching for the continuation of the treatment.

However, there is no clinical study to support this assertion. The objective of this study is to monitor and correlate the therapeutic effect of Metformin on patients with PCOS taking daily doses of 1500mg and 1000mg.

Patients with PCOS diagnosis and that are able to attempt the inclusion criteria are divided in two groups: administration of metformin 500 mg tablet three times/day as well 1500 mg/day (group A)and administration of metformin 500 mg tablet twice/day or 1000 mg/day (group B). Blood samples were collected to the pharmacokinetic evaluation from first day of administration until 3 months after beginning of treatment. The patients are monitored during 3 months and all side effects are register. The efficacy of both treatment are analyzed by biochemical and physical evaluation.

Inclusion Criteria:

• Patients aged between 18 and 40 years old, with no use of contraceptive drugs or insulin sensitizing agents for more than 3 months.
• PCOS diagnosis.
• Insulin resistance Index by the Homeostatic model Assessment Formula higher than 2.5.

Exclusion Criteria:

• Another diseases with androgen excess;
• Patients with history of serious adverse reaction or hypersensibility to any medicine;
• History or presence of renal, hepatic or gastrointestinal disorders.
• Continuous use of any pharmaco, inclusively metformin