Trimethoprim for infections
Revisado por Sid DajaniÚltima actualización por Michael Stewart, MRPharmSÚltima actualización: 5 de mayo de 2025
Satisface las necesidades del paciente directrices editoriales
- DescargarDescargar
- Compartir
Trimethoprim is an antibacterial medicine prescribed for treating infections, mainly chest or urine infections. It is sometimes prescribed to prevent an infection.
Space out your doses evenly throughout the day, and remember to finish the full course of treatment.
The most common side-effects are feeling sick (nausea), and a mild itchy rash.
En este artículo:
Seguir leyendo
About trimethoprim
Tipo de medicamento | An antibacterial medicine |
Utilizado para | Bacterial infections (in adults and children) |
Disponible como | Comprimidos y medicamentos orales líquidos |
Trimethoprim is given to treat a bacterial infection. It is mainly prescribed for urine infections, but it is also prescribed for chest infections and some other types of infection. It works by killing the germs (bacteria) responsible for the infection.
A urine infection is often called a urinary tract infection (UTI) by doctors. Most urine infections are caused by bacteria that come from your own bowel. They are usually easily treated with a short course of trimethoprim. Occasionally, longer-term treatment may be needed to prevent the infection from recurring.
Before taking trimethoprim
Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking trimethoprim it is important that your doctor knows:
Si está embarazada, esperando un bebé o en período de lactancia.
If you know you have low amounts of the vitamin folic acid.
Si tiene problemas con el funcionamiento de los riñones.
Si tiene problemas con el funcionamiento del hígado.
If you have a blood disorder, or if you have a rare inherited blood disorder called porphyria.
Si está tomando otros medicamentos. Esto incluye todos los medicamentos que se pueden comprar sin receta, así como las hierbas medicinales y los medicamentos complementarios.
Si alguna vez ha tenido una reacción alérgica a un medicamento.
Seguir leyendo
How to take trimethoprim
Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about trimethoprim and will provide you with a full list of the side-effects which you could experience from taking it.
Take trimethoprim tablets exactly as your doctor tells you to. Your dose will depend upon whether you are being treated because you have an infection, or to prevent an infection. As a guide, the dose for adults with an infection is 200 mg twice daily, taken morning and evening. The adult dose to prevent an infection is 100 mg at night. If trimethoprim has been prescribed for a child, it is likely that you will be supplied a liquid medicine - the dose will depend upon the age of the child, so read the directions on the label carefully to make sure you give the correct dose.
Space your doses out evenly throughout the day - this means that tablets/medicine prescribed twice daily should be taken every 12 hours. Swallow the tablet with a drink of water. You can take trimethoprim either with or without food.
Even if you feel your infection has cleared up, keep taking trimethoprim until the full course is finished (unless a doctor tells you to stop). This is to prevent the infection from coming back. A normal course of treatment is likely to last 3-14 days. The course will be for longer than this if you are taking trimethoprim to prevent recurrent infections.
If you forget to take a dose at the correct time, take one as soon as you remember. Try to take the correct number of doses each day. Do not take two doses at the same time to make up for a forgotten dose.
Aproveche al máximo su tratamiento
Most people improve within a few days of starting treatment. If your symptoms do not improve despite taking trimethoprim, go back to see your doctor, as you may need an alternative medicine. This is because some bacteria are resistant to some types of antibiotics.
If you are taking the contraceptive 'pill' at the same time as this antibacterial medicine, the effectiveness of the 'pill' can be reduced if you have a bout of being sick (vomiting) or diarrhoea which lasts for more than 24 hours. If this should happen, ask your doctor or pharmacist for advice about what additional contraceptive precautions to use over the following few days. There is no need to use additional precautions for any bouts of sickness or diarrhoea which last for less than 24 hours.
Trimethoprim can stop the oral typhoid vaccine from working. If you are due to have any vaccinations, make sure the person treating you knows that you are taking it.
Seguir leyendo
Can trimethoprim cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with trimethoprim. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.
Very common trimethoprim side-effects (these affect more than 1 in 10 people) | ¿Qué puedo hacer si me ocurre esto? |
Sentirse mal (náuseas) o estar enfermo (vómitos) | Stick to simple foods - avoid fatty or spicy meals. If you are not already doing so, try taking trimethoprim after food |
Common trimethoprim side-effects (these affect fewer than 1 in 10 people) | ¿Qué puedo hacer si me ocurre esto? |
Diarrea | Drink plenty of water to replace lost fluids. Stick to simple foods |
Dolor de cabeza | Bebe mucha agua y pide a tu farmacéutico que te recomiende un analgésico adecuado. Si los dolores de cabeza persisten, informe a su médico. |
Erupción cutánea con picor | Try applying a gentle, fragrance-free skin moisturiser. If the rash becomes troublesome or severe, speak with your doctor |
Important: if trimethoprim is taken over a long period of time (such as when it is taken long-term to prevent an infection), it can occasionally cause problems. If you develop a high temperature (fever), sore throat, skin rash, mouth ulcers or any bruising or bleeding which you can't explain, you should let your doctor know about this straightaway. These may be signs of a blood disorder.
Si experimenta cualquier otro síntoma que considere que puede deberse a este medicamento, consulte a su médico o farmacéutico.
How to store trimethoprim
Mantenga todos los medicamentos fuera del alcance y de la vista de los niños.
Almacenar en un lugar fresco y seco, lejos del calor y la luz directos.
Información importante sobre todos los medicamentos
Información importante sobre todos los medicamentos
No tome nunca más de la dosis prescrita. Si sospecha que usted u otra persona ha tomado una sobredosis de este medicamento, acuda inmediatamente al servicio de urgencias de su hospital. Llévese el envase, aunque esté vacío.
Este medicamento es para usted. Nunca se lo dé a otras personas aunque su enfermedad parezca ser la misma que la suya.
Si compra algún medicamento, compruebe con un farmacéutico que es seguro tomarlo con sus otros medicamentos.
Si va a someterse a una operación o a un tratamiento dental, comunique a la persona que lleve a cabo el tratamiento qué medicamentos está tomando.
No guarde medicamentos caducados o que no desee. Llévelos a su farmacia local, que se encargará de eliminarlos por usted.
Si tiene cualquier duda sobre este medicamento pregunte a su farmacéutico.
Informar de los efectos secundarios de un medicamento o vacuna
Si experimenta efectos secundarios, puede notificarlos en línea a través del sitio web de la Tarjeta Amarilla.
Lecturas complementarias y referencias
- Manufacturer's PIL, Trimethoprim 50 mg/5 ml Suspension; Pinewood Healthcare, The electronic Medicines Compendium. Dated June 2019.
- Medicamentos BNF completa 89ª edición; Asociación Médica Británica y Real Sociedad Farmacéutica de Gran Bretaña, Londres.
Historia del artículo
La información de esta página ha sido redactada y revisada por médicos cualificados.
Fecha prevista para la próxima revisión: 5 de mayo de 2028
5 de mayo de 2025 | Última versión

Pregunte, comparta, conecte.
Explore debates, formule preguntas y comparta experiencias sobre cientos de temas de salud.

¿Se encuentra mal?
Evalúe sus síntomas en línea de forma gratuita