 sulfamethoxazole and trimethoprim is taken by mouth (oral) or given as an infusion into a vein (injection).
Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.
Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).
A healthcare provider will give the first injection and may teach you how to properly use the medication by yourself. When using injections by yourself, be sure you understand how to properly mix and store the medicine. Ask your doctor or pharmacist if you don't understand all instructions.
Drink plenty of fluids to prevent kidney stones while you are using this medicine.
Sulfamethoxazole and trimethoprim doses are based on weight in children. Use only the recommended dose when giving this medicine to a child.
Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses can increase your risk of infection that is resistant to medication. This medicine will not treat a viral infection such as the flu or a common cold.
You may need frequent medical tests.
This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using sulfamethoxazole and trimethoprim.
Store at room temperature away from moisture, heat, and light.
 Detailed Sulfamethoxazole/trimethoprim dosage information
What happens if I miss a dose?
Use the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not use two doses at one time.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include loss of appetite, vomiting, fever, blood in your urine, yellowing of your skin or eyes, confusion, or loss of consciousness.
