Sexual Side Effects

• In clinical studies with dutasteride, as detailed by eMedTV, the most common side effects were temporary and occurred in about 1 to 4 percent of participants. These included erectile dysfunction, impotence, decreased sex drive and abnormal ejaculation, such as decreased amounts of semen.
  
  

Breast Changes

• Up to 1 percent of men in some of these studies experienced breast changes, such as tenderness, enlargement, lumps or discharge. Patients with these side effects should consult a doctor.
  
  

Other Side Effects

• Other side effects associated with dutasteride include dizziness, headache, musculoskeletal pain, generally not feeling well and ear, nose and throat infections.
  
  

Allergic Reaction

• Rarely, some people have an allergic reaction to dutasteride. Signs are rash, itching, dizziness, swelling and difficulty breathing.
  
  

Drug Interactions

• Dutasteride can interact with many other drugs. These include certain medications that treat human immunodeficiency virus (HIV), antidepressants, antifungal drugs, antibiotics, prescription pain medications and high blood pressure medicines.