Co-trimoxazole is used to treat certain bacterial infections, such as pneumonia (a lung infection), bronchitis (infection of the tubes leading to the lungs), and infections of the urinary tract, ears, and intestines. It also is used to treat ‘travelers’ diarrhea. Co-trimoxazole is a combination of trimethoprim and sulfamethoxazole and is in a class of medications called sulfonamides. It works by stopping the growth of bacteria. Antibiotics will not kill viruses that can cause colds, flu, or other viral infections.

Co-trimoxazole comes as a tablet and a suspension (liquid) to take by mouth. It usually is taken two times a day but may be taken up to four times a day when used to treat certain severe lung infections. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take co-trimoxazole exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

You should begin to feel better during the first few days of treatment with co-trimoxazole. If your symptoms do not improve or if they get worse, call your doctor.

Shake the liquid well before each use to mix the medication evenly.

Take co-trimoxazole until you finish the prescription, even if you feel better. Do not stop taking co-trimoxazole without talking to your doctor. If you stop taking co-trimoxazole too soon or skip doses, your infection may not be completely treated and the bacteria may become resistant to antibiotics.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking co-trimoxazole,

• Tell your doctor and pharmacist if you are allergic to co-trimoxazole, any other medications, or any ingredients in co-trimoxazole tablets and suspension. Ask your pharmacist for a list of ingredients.
• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention the following: amantadine; angiotensin converting enzyme inhibitors such as benazepril (Lotensin), captopril (Capoten), enalapril (Vasotec), fosinopril (Monopril), lisinopril (Prinivil, Zestril), moexipril (Univasc), perindopril (Aceon), quinapril (Accupril), ramipril (Altace), and trandolapril (Mavik); anticoagulants (‘blood thinners’) such as warfarin (Coumadin, Jantoven); cyclosporine (Gengraf, Neoral, Sandimmune); oral diabetes medications such as glipizide (Glucotrol), glyburide (Diabeta, Glynase), metformin (Fortamet, Glucophage), pioglitazone (Actos), repaglinide (Prandin), rosiglitazone (Avandia); digoxin (Lanoxin); diuretics (‘water pills’); indomethacin (Indocin); leucovorin (Fusilev); medications for seizures such as phenytoin (Dilantin, Phenytek); memantine (Namenda); methotrexate (Trexall); pyrimethamine (Daraprim). and tricyclic antidepressants such as amitriptyline (Elavil), amoxapine (Asendin), desipramine (Norpramin), doxepin (Adapin, Sinequan), imipramine (Tofranil), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), and trimipramine (Surmontil). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• Tell your doctor if you have or have ever had thrombocytopenia (less than normal number of platelets) caused by taking sulfonamides or trimethoprim; megaloblastic anemia (abnormal red blood cells) caused by folate deficiency (low blood levels of folic acid), phenylketonuria (PKU, an inherited condition in which a special diet must be followed to prevent damage to your brain that can cause severe intellectual disability), or liver or kidney disease. Your doctor may tell you not to take co-trimoxazole. Co-trimoxazole should not be used in children less than 2 months of age.
• Tell your doctor if you have or have ever had severe allergies; asthma; low levels of folic acid in the body which may be caused by malnutrition (you do not eat or cannot digest the nutrients needed for good health); human immunodeficiency virus (HIV) infection; porphyria (an inherited blood disease that may cause skin or nervous system problems); thyroid disease; or glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (an inherited blood disease).
• Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking co-trimoxazole, call your doctor immediately. Co-trimoxazole can harm the fetus.
• Plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Co-trimoxazole may make your skin sensitive to sunlightP

Unless your doctor tells you otherwise, continue your normal diet.

Drink plenty of fluids during your treatment with co-trimoxazole.

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Co-trimoxazole may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Nausea
• Vomiting
• Loss of appetite

If you experience any of the following symptoms, call your doctor immediately:

• Rash
• Itching
• Sore throat
• Fever or chills
• Severe diarrhea (watery or bloody stools) that may occur with or without fever and stomach cramps (may occur up to 2 months or more after your treatment)
• Shortness of breath
• Cough
• Unusual bruising or bleeding
• Yellowing of the skin or eyes
• Paleness
• Red or purple skin discolorations
• Joint or muscle pain

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to co-trimoxazole.

Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking co-trimoxazole.

Do not let anyone else take your medication. Your prescription is probably not refillable. If you still have symptoms of infection after you finish the co-trimoxazole, call your doctor.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.