However, Sancton says Viagra is only indicated for the treatment of erectile dysfunction. Dr. Alvaro Morales, the Queen's University professor of urology who headed the drug's Canadian trials, says patients have to be warned of potential side effects and doctors need to take some precautions before prescribing it. The drug should only be considered only after a physical examination and medical history have confirmed a diagnosis of erectile dysfunction and determined any underlying causes, such as diabetes, that may also require treatment. Patients taking nitrates in any form, including nitroglycerin and long-acting nitrates commonly used for chest pain, should not take Viagara because large and sudden drops in blood pressure can occur when the drugs are combined. They may have heart palpitations during sex and decide to take nitrates.
Patients have to be warned of common side effects.
Morales says all side effects disappear within 3 to 4 hours. Warn patients not to take more than 1 tablet per day, and never more than 100 mg, says Morales. Beyond 100 mg the efficacy doesn't increase but the potential side effects double.