Trimethoprim comes as a tablet and a liquid to take by mouth. It usually is taken two times a day but may be taken up to four times a day for severe lung infections. Drink a full glass of water with each dose.
Shake the liquid well before each use to mix the medication evenly. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take trimethoprim exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Take this medication by mouth, usually 3 times a day or as directed by your doctor. In general, your doctor may slowly increase your dose to lower your chance of side effects until the right dose for you is determined.
Drowsiness, dizziness, weakness, tiredness, headache, trouble sleeping, nausea, or constipation may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of these unlikely but serious side effects occur: mental/mood changes (e.g., confusion, depression, hallucinations), hearing/vision changes, seizures, fast/pounding heartbeat, fainting, black/bloody stools.
Seek immediate medical attention if any of these rare but very serious side effects occur: chest pain, shortness of breath.
A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching, swelling, severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.
Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away. Do not breastfeed while using the medicine.
Very rarely, this medicine has caused severe side effects. If you start to have a skin rash, or if you think you are having a severe skin reaction, stop taking this medicine and call your doctor right away. Symptoms of a severe reaction may include a skin rash, skin color that is very pale or yellow, or skin with purple spots, along with a sore throat, fever, muscle pain, cough, and trouble with breathing.
Check with your doctor right away if you have abdominal or stomach cramps; bloating; watery and severe diarrhea, which may also be bloody; nausea or vomiting; or unusual tiredness or weakness. These may be symptoms of a serious intestinal infection.
This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Check with your doctor right away if you have a rash; itching; swelling of the face, tongue, and throat; trouble with breathing; shortness of breath; or chest pain after you use the medicine.
Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop or change the dosage of any medicine before checking with them first.
Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use.
Tell your doctor or pharmacist if you also take drugs that cause drowsiness such as certain antihistamines (e.g., diphenhydramine), anti-seizure drugs (e.g., carbamazepine), medicine for sleep or anxiety (e.g., alprazolam, diazepam, zolpidem), other muscle relaxants, narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., chlorpromazine, risperidone, trazodone).
Check the labels on all your medicines (e.g., cough-and-cold products) because they may contain drowsiness-causing ingredients. Ask your pharmacist about the safe use of those products.
Also report the use of drugs which might increase seizure risk (decrease seizure threshold) when combined with baclofen such as isoniazid (INH), phenothiazines (e.g., thioridazine), theophylline, or tricyclic antidepressants (e.g., amitriptyline), among others. Consult your doctor or pharmacist for details.
This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.
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.
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). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.