Triméthoprime
antibiotic
Third-party optionBy the Layer Nutrition editorial team · How the atlas classifies the 664 molecules
What this medicine is for
Trimethoprim is a medicine in the “antibiotic” category. Antibiotics treat infections caused by bacteria. They are taken as a course, over a set period, to the end of the prescription.
Specifically, for Trimethoprim: Treats a bacterial infection. It is used rather occasionally or as a short course, to get through an episode.
Under which brands it is found
In France, about 4 reimbursable presentations containing Trimethoprim are recorded. It comes under various trade names and in generic form.
- Bactrim
- Bactrim Forte
- Cotrimoxazole Teva
- Delprim
Generics and the original brand are equivalent for the active substance; only the appearance, the name or the excipients may differ.
On your plate: folates (vitamin B9)
In prolonged treatment, trimethoprim can lower the reserves of folates, the vitamin B9 needed to produce red blood cells. Diet helps maintain these reserves, meal after meal, alongside your treatment.
Folates are concentrated in green leafy vegetables such as spinach and kale, in legumes such as lentils, chickpeas and beans, as well as in broccoli, beetroot and avocado. Citrus fruits, in particular the orange, also provide a worthwhile amount.
Many of these foods combine folates and fibre: lentils, chickpeas, spinach, broccoli. Spreading them across the day, a portion of legumes at lunch and green vegetables at dinner, covers a good part of the B9 requirements without any particular effort.
How trimethoprim works
Trimethoprim is an antibiotic that blocks a specific enzyme, dihydrofolate reductase. This enzyme converts dihydrofolic acid into tetrahydrofolic acid, an essential step in the production of folates within the bacterium. By inhibiting it, trimethoprim halts the bacterial synthesis of folates and then that of nucleic acids. Deprived of these building blocks, the bacterium can no longer multiply.
Its action targets the bacterium far more than our own cells. Trimethoprim has a markedly stronger affinity for bacterial dihydrofolate reductase than for the equivalent human enzyme. This selectivity explains why it attacks the germ while largely sparing the body.
Why it is prescribed
Trimethoprim is used to prevent and treat urinary tract infections, as well as other infections caused by susceptible germs. It is particularly well suited to conditions of the urinary tract, because a substantial share of the drug reaches the urine directly.
After absorption, 40 to 50 percent of the dose is eliminated unchanged in the urine within 24 hours. The active substance therefore concentrates where the urinary infection takes place, which supports its use in this indication. The choice of the molecule always depends on the susceptibility of the germ involved, as assessed by the physician.
How to take it day to day
For an acute urinary tract infection in adults, the usual dosage is 200 mg twice a day, that is one dose every 12 hours. Trimethoprim can be taken with or without food. In case of nausea, taking it during a meal is acceptable and does not affect its effectiveness.
The peak concentration occurs about 3 hours after the dose, and the half-life is between 10 and 16 hours when kidney function is normal; it lengthens in cases of renal impairment. Taking the doses regularly maintains a stable level in the blood. You should not change the dose or stop the treatment on your own initiative, even when the symptoms fade: it is the physician who sets the duration.
The effects to know about and their frequency
The most common effect concerns blood potassium: hyperkalaemia, meaning a rise in potassium, is very common and affects at least 1 person in 10. Next come common effects, between 1 case in 100 and 1 case in 10: nausea, diarrhoea, headache and skin rash.
More serious effects exist, but they remain very rare, at fewer than 1 case in 10,000. These include blood disorders such as leukopenia, neutropenia, thrombocytopenia, agranulocytosis, megaloblastic anaemia and aplastic anaemia, as well as hyponatraemia and severe skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. Any unexplained fever, any persistent sore throat or any widespread rash warrants prompt medical advice.
Folates and megaloblastic anaemia
By blocking dihydrofolate reductase, trimethoprim affects an enzyme that both the bacterium and the human body use, even if the affinity for the human form remains low. In prolonged treatment, it can therefore promote megaloblastic anaemia linked to a folate deficiency. If such a deficiency appears, the physician administers calcium folinate, also known as folinic acid, which restores the folate pathway.
A monthly blood check is advised during long treatments, in people already deficient in folates and in older people. This monitoring detects a decline before it becomes problematic. Diet remains the simplest way to maintain these reserves day to day.
Interactions and monitoring
Several combinations call for particular vigilance. With warfarin, trimethoprim can increase the risk of bleeding. It also increases the toxicity of methotrexate and the risk of megaloblastic anaemia, raises digoxin levels, and its combination with dofetilide is contraindicated because of a risk of torsades de pointes. The risk of hyperkalaemia increases in cases of renal impairment or when combined with drugs that raise potassium, such as angiotensin-converting enzyme inhibitors.
Laboratory monitoring frames the treatment. Kidney function and serum electrolytes are monitored, particularly during prolonged use. This check makes it possible to detect hyperkalaemia or a fall in blood cell lines early, and to adjust the approach if needed. The complete list of medicines being taken should be shared with the physician and the pharmacist.
Sources
Related molecules
To explore in the « Anti-infectives » family and its neighbours.
See the whole « Anti-infectives » family · Back to the atlas
Supplements to consider
Beyond the plate, a single isolated nutrient can be worth discussing, to confirm with your doctor or pharmacist. Here is which one and in which form.
Probiotics
Probiotics are live micro-organisms, mainly lactobacilli and bifidobacteria. The CFU count and the number of strains are among the selection criteria; gastro-resistant capsules protect the bacteria from stomach acidity.
Preferred form gastro-resistant capsules, several strains, CFU count stated
Frequently asked questions
What is trimethoprim used for?
Trimethoprim is an antibiotic used in particular for certain urinary tract infections, either on its own or combined with sulfamethoxazole. For the exact indication that applies to you, refer to the patient leaflet and ask your doctor or pharmacist for advice.
What are the side effects of trimethoprim?
The patient leaflet mainly mentions digestive problems such as nausea or vomiting, as well as skin rashes and itching. A change in blood potassium levels is also possible. The complete list is given in the patient leaflet; if you notice any symptom, talk to your doctor or pharmacist.
Can you take trimethoprim during pregnancy?
Trimethoprim acts on the folate pathway, which explains the specific precautions described in the patient leaflet, especially in early pregnancy. If you are pregnant or planning to be, do not adjust anything on your own and speak to your doctor.
What does trimethoprim interact with?
The patient leaflet notes interactions in particular with methotrexate, with certain medicines that affect potassium, and with certain anticoagulants. As this list is not exhaustive, have all of your treatments checked by your doctor or pharmacist.
Can trimethoprim affect your folate levels?
Trimethoprim inhibits dihydrofolate reductase, the central enzyme of the folate pathway, and studies link this class of antibiotics to folate metabolism. From a nutritional standpoint, the nutrient to consider is folate, in the form of methylfolate (5-MTHF) or folic acid. The decision and its follow-up are for your doctor to make.
Should you look after your gut flora when taking an antibiotic like trimethoprim?
Like antibiotics in general, trimethoprim can disrupt the balance of the gut flora for the duration of the treatment. The active often considered in this context is a probiotic, taken apart from the antibiotic dose. Ask your doctor or pharmacist what is right for your situation.
Ces réponses portent sur le volet nutritionnel. Pour toute question sur votre médicament, la notice et votre médecin ou pharmacien font foi.