Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. This includes prescription or nonprescription over-the-counter [OTC] medicines and herbal or vitamin supplements. Storage Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Read more on male sexual health on the Sexual Health Australia site. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse.Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. Sildenafil . Sildenafil may be used to treat erectile dysfunction (ED or impotence) in men (Viagra brand) or pulmonary arterial hypertension in both men and women (Revatio brand), depending on the brand. and your doctor can advise you on an alternative. Call your doctor immediately if you experience dizziness or feel nauseous during sexual activity, . A person needs a prescription for medications such as Viagra or Cialis. A primary care physician or a doctor at a telehealth company can provide it.