POM: Prescription only medicine
This information is intended for use by health professionals
Trimethoprim 200mg Tablets
Each tablet contains Trimethoprim 200 mg
Flat white tablet, with bevelled edges and embossed with 'TR200' on one side.
Treatment of susceptible infections caused by trimethoprim sensitive organisms including urinary and respiratory tract infections.
Prophylaxis of recurrent urinary tract infections.
Treatment should continue for a period of between 3 days (eg, uncomplicated bacterial cystitis in women) to 2 weeks depending on the nature and severity of the infection. The first dose may be doubled.
Adults: 200mg twice daily
Children over 12 years: same as adult dose
Children 6 - 12 years: 100mg twice daily
Children under 6 years: This dosage form is not suitable for use in children younger than 6 years.
Elderly: Dosage is dependent on renal function. See special dosage schedule below.
Advised dosage schedule where there is reduced kidney function:
Creatinine Clearance (ml/sec)
Plasma creatinine (micromol/l)
0.25 - 0.45
Normal for 3 days then half dose
Half the normal dose
Trimethoprim is removed by dialysis. However, it should not be administered to dialysis patients unless plasma concentrations can be estimated regularly.
Long-term treatment and prevention therapy:
Adults: 100mg at night
Children over 12 years: Same as adult dose
Children 6-12 years: 50mg at night. Where a single daily dose is required, dosage at bedtime may maximise urinary concentrations. The approximate dosage in children is 2mg trimethoprim per kg body weight per day.
Elderly: Dose depends on renal function. Refer to special dosage schedule above.
Method of administration
For oral administration.
Severe hepatic insufficiency. Severe renal insufficiency. Megaloblastic anaemia and other blooddyscrasias. Trimethoprim should not be administered to premature infants or children under 4 months of age. Trimethoprim should not be administered to pregnant women.
Hypersensitivity to trimethoprim or any other constituents of the medication. (listed in section 6.1)
Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Trimethoprim should not be administered to pregnant women, premature infants or infants during the first few weeks of life.
Patients with marked impairment of renal function: Care should be taken to avoid accumulation and resulting adverse hepatological effect.
Trimethoprim may cause depression of haemopoiesis. Regular haematological tests should be undertaken in patients receiving long term treatment and those predisposed to folate deficiency, (e.g. the elderly), to check for possible pancytopaenia. Although an effect on folate metabolism is possible, interference with haematopoiesis rarely occurs at the recommended dose. If any such change is seen, folinic acid should reverse the effect. Elderly people may be more susceptible and a lower dose may be advisable. If there is evidence of folic acid deficiency, calcium folinate should be administered and response checked by haematologic monitoring. It may be necessary to discontinue trimethoprim. Particular care should be exercised in the haematological monitoring of children on long term therapy.
Close monitoring of serum electrolytes is advised in patients at risk for hyperkalaemia (see section 4.8).
Concomitant use of medicinal products known to cause hyperkalaemia with Trimethoprim may result in severe hyperkalaemia.
Monitoring of blood glucose is advised if co-administered with repaglinide (see section 4.5). Acute porphyria
Folate antagonists and anticonvulsants: Trimethoprim may induce folate deficiency in patients predisposed to folate deficiency such as those receiving concomitant folate antagonists or anticonvulsants.
Bone marrow depressants: Trimethoprim may increase the risk for bone marrow aplasia. Cytotoxic agents such as azathioprine, mercaptopurine and methotrexate increase the risk of hematologic toxicity when given with trimethoprim.
Special care is necessary in patients receiving pyrimethamine in addition to trimethoprim.
Phenytoin and Digoxin: Careful monitoring of patients treated with digoxin or phenytoin is advised as trimethoprim may increase plasma concentration of these agents by increasing their elimination half- life.
Rifampicin may decrease trimethoprim concentrations.
Diuretics: In elderly patients taking diuretics, particularly thiazides, there is an increased incidence of thrombocytopenia with purpura.
Hyperkalaemia may be exacerbated by concomitant administration of diuretics, particularly potassium sparing diuretics and/or thiazide diuretics and eplerenone.
In addition to other medicinal products known to cause hyperkalaemia concomitant use of trimethoprim with spironolactone may result in clinically relevant hyperkalaemia
Cyclosporin: Increased risk of nephrotoxicity.
Procainamide: Trimethoprim increases plasma concentrations of procainamide.
Dapsone: Plasma concentrations of trimethoprim and dapsone may increase when taken together.
Repaglinide: Trimethoprim may enhance the hypoglycaemic effects of repaglinide.
Anticoagulants: Trimethoprim may potentate the anticoagulant effect of warfarin and other coumarins.
Antibacterials: Plasma concentration of trimethoprim is possibly reduced by rifampicin. Plasma concentration of both drugs may increase when trimethoprim is given with dapsone.
Antimalarials: Increased antifolate effect when trimethoprim is given with pyrimethamine.
Trimethoprim is contraindicated in pregnant women, premature infants or infants during the first few weeks of life.
Although Trimethoprim is excreted in breast milk, it is not necessarily contraindicated for short- term therapy during lactation. This should be kept in mind when considering administration to breast- feeding women.
None that are known.
The following list of undesirable effects have been reported by health care professionals. Sometimes it may be difficult to distinguish reactions caused by the condition being treated from adverse drug reactions, which means that not all the listed reactions were caused by drug administration.
The most frequent adverse effects at usual doses are pruritus and skin rash (in about 3 to 7% of patients) and mild gastrointestinal disturbances including nausea, vomiting and glossitis. These effects are generally mild and quickly reversible on withdrawal of the drug.
Infections and Infestations
Common: Monilial overgrowth
Blood and lymphatic system disorders
Very rare: Leucopenia, neutropenia, thrombocytopenia, pancytopaenia, bone marrow depression, agranulocytosis, aplastic anaemia, haemolytic anaemia, eosinophilia, purpura, haemolysis,
Unknown: Megaloblastic anaemia, methaemoglobinaemia, hyperkalaemia (particularly in the elderly and in HIV patients), methaemoglobinaemia. Trimethoprim therapy may effect haematopoiesis.
Fatalities have been reported (especially in the elderly, or those with impairment of renal or hepatic function in whom careful monitoring is advised- refer to Section 4.3 Contraindications), however the majority of haematological changes are mild and reversible when treatment is stopped.
Immune system disorders
Very rare: Hypersensitivity, anaphylaxis, anaphylactoid reaction drug fever, allergic vasculitis resembling Henoch-Schoenlein purpura, periarteritis nodosa, systemic lupus erythematosus.
Metabolism and nutrition disorders
Very common: Hyperkalaemia
Very rare: Hypoglycaemia, hyponatraemia, anorexia
Close supervision is recommended when Trimethoprim is used in elderly patients or in patients taking high doses as these patients may be more susceptible to hyperkalaemia and hyponatraemia
Very rare: Depression, hallucinations, confusional states, agitation, anxiety, abnormal behavior, insomnia and nightmares.
Nervous system disorders
Very rare: Dyskinesias, aseptic meningitis, tremor, ataxia, dizziness, lethargy, syncope, paraesthesiae, convulsions, peripheral neuritis, vertigo, tinnitus.
Aseptic meningitis was rapidly reversible on withdrawal of the drug, but recurred in a number of cases on re-exposure to either co-trimoxazole or to Trimoptin alone.
Very rare: uveitis
Respiratory, thoracic and mediastinal disorders
Very rare: Cough, shortness of breath, wheeze, epistaxis
Common: Nausea, diarrhoea, vomiting.
Very rare: Constipation, glossitis, stomatitis, pseudomembranous colitis, pancreatitis.
Unknown: Sore mouth
Very rare: Disturbance in liver enzymes, elevation of serum transaminases, elevation of bilirubin levels, cholestatic jaundice, hepatic necrosis. Cholestatic jaundice and hepatic necrosis may be fatal.
Skin and subcutaneous tissue disorders
Common: Skin rashes, urticaria
Very rare: Photosensitivity, exfoliative dermatitis, fixed drug eruption, erythema multiforme, erythema nodusum, Stevens-Johnson Syndrome, toxic epidermal necrolysis, bullous dermatitis, purpura, angioedema
Lyell's syndrome (toxic epidermal necrolysis) carries a high mortality.
Musculoskeletal and connective tissue disorders
Very rare: Arthralgia, myalgia and uveitis
Renal and urinary disorders
Very rare: Impaired renal function (sometimes reported as renal failure), haematuria
Unknown: Raised serum creatinine and blood urea nitrogen levels. It is not known however, whether this represents inhibition of creatinine tubular secretion or genuine renal dysfunction.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the yellow card scheme at www.mhra.gov.uk/yellowcard.
Treat symptomatically, gastric lavage and forced diuresis can be used.
Depression of haematopoiesis by trimethoprim can be counteracted by intramuscular injections of calcium folinate.
Pharmacotherapeutic group: Systemic antibacterial.
ATC Code: J01EA01
Mechanisms of action
Trimethoprim is a dihydrofolate reductase inhibitor which affects the nucleoprotein metabolism of micro-organisms by interference in the folic-folinic acid systems, inhibiting the conversion of bacterial dihydrofolic acid to tetrahydrofolic acid, required for the synthesis of some amino acids.
Its effects are considerably greater on the cells of micro-organisms than on the mammalian cells. Trimethoprim may be bactericidal or bacteriostatic depending on growth conditions.
In vitro trimethoprim has effects on most Gram-positive and Gram-negative aerobic organisms, including enterobacteria such as E Coli, Proteus, Klebsiella pneumoniae, Streptococcus faecalis, Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus.
It has no effect on Mycobacterium tuberculosis, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Treponema pallidum, Brucella abortis or anaerobic bacteria.
Mechanism(s) of resistance
Resistance to trimethoprim may be due to several mechanisms. Clinical resistance is often due to plasmid mediated dihydrofolate reductases that are resistant to trimethoprim: such genes may become incorporated into the chromosome via transposons. Resistance may also be due to overproduction of dihydrofolate reductase, changes in cell permeability, or bacterial mutants which are intrinsically resistant to trimethoprim because they depend on exogenous thymidine and thymine for growth. Emergence of resistance to trimethoprim does not appear to be any higher in areas where it is used alone than in areas where trimethoprim is used in combination with sulphonamides. Nonetheless, trimethoprim resistance has been reported in many species, and very high frequencies of resistance have been seen in some developing countries, particularly among Enterobacteriaceae.
EUCAST clinical MIC breakpoints to separate susceptible (S) pathogens from resistant (R) pathogens are:
EUCAST Species-related breakpoints (Susceptible≤/Resistant>) Units: mg/L
*The activity of trimethoprim is uncertain against enterococci. Hence thewild type population is categorized as intermediate.
Trimethoprim is rapidly and almost completely absorbed from the gastrointestinal track and peak concentration in the circulation occur about 1-4 hours after an oral dose. Peak plasma concentrations of about 1µg/ml have been reported after a single dose of 100mg. Approximately 40-70% is bound to plasma proteins. Tissue concentrations are reported to be higher than serum concentrations with particularly high concentrations occurring in the kidneys and lungs but concentrations in the cerebrospinal fluid are about one half of those in the blood. About 40 to 60% of a dose is excreted in the urine within 24 hours (mainly as unchanged drug) together with metabolites; hence, patients with impairment of renal function such as the elderly may require a reduction in dosage due to accumulation. Urinary concentrations are generally well above the MIC of common pathogens for more than 24 hours after the last dose. The half-life is approximately 8- 10 hours. It appears in breast milk.
Sodium starch glycolate (Type A)
Store below 25°C in a dry place. Protect from light.
Polypropylene securitainer of 14/15/18/20/21/28/30/100/500 100 or 500 tablets with appropriate bellows or polyurethane foam wads.
Also available in a PVC blister with aluminium lidding foil containing 6, 14 and 28 tablets.
No special instructions
Athlone Laboratories Limited
Joshna House, Crowbridge Road, Orbital Park, Ashford, Kent, TN24 0GR
0845 437 5567
0845 437 5565
+44 (0)1233 506 574
0800 220 280