TRIMETHOPRIM TABLETS B.P. 100MG
NAME OF THE MEDICINAL PRODUCT
Trimethoprim 100 mg Tablets B.P.
QUALITATIVE AND QUANTITATIVE COMPOSITION
Trimethoprim is indicated in the treatment of urinary tract infections and acute
and chronic bronchitis.
It may also be used in the long term prophylaxis of urinary tract infections.
Posology and method of administration
Treatment should continue for a period of between three days (e.g.
uncomplicated bacterial cystitis in women) and two weeks according to the
nature and severity of infection. The first dose can be doubled.
Adults and children over 12 years: 200 mg twice daily.
Children 6 to 12 years: 100 mg twice daily.
Children under 6 years of age: Not recommended; a more suitable dosage
form should be used in this age group.
Elderly: Dosage is dependent upon kidney function; see special dosage
Long-term treatment and prophylactic therapy:
Adults and children over 12 years: 100 mg at night.
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: Dosage is dependent on kidney function; see special dosage schedule
Advised dosage schedule where there is reduced kidney function:
Men < 250
Women < 175
0.25 – 0.45
Men 250 – 600
Women 175 – 400
Men > 600
Normal for 3 days then
Half the normal dose
Women > 400
Trimethoprim is removed by dialysis. However, it should not be administered to
dialysis patients unless plasma concentrations can be estimated regularly.
Route of administration
For oral administration.
Hypersensitivity to trimethoprim or any of the excipients, pregnancy,
neonates, blood dyscrasias, severe renal insufficiency where blood levels
cannot be regularly monitored.
Special warnings and precautions for use
Administer with care to patients with impaired renal function. Regular
haematological examination should be performed during long-term therapy.
Caution should be exercised in the administration of trimethoprim to patients
with acute or potential folate deficiency (e.g. the elderly) and administration of
folate supplement should be considered.
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.
In patients with renal impairment, care should be taken to avoid accumulation.
Interaction with other medicinal products and other forms of interaction
Concomitant administration with methotrexate may give rise to an increased
Special care is necessary in patients receiving pyrimethamine therapy in
addition to trimethoprim.
Bone marrow depressants - trimethoprim may increase the potential for bone
Rifampicin may increase the elimination and shorten the elimination half-life
Phenytoin and digoxin – the patient should be carefully controlled as
trimethoprim may increase the elimination half-life of phenytoin and digoxin.
Trimethoprim may potentiate the anticoagulant effect of warfarin.
Ciclosporin may increase the nephrotoxicity of trimethoprim.
Fertility, pregnancy and lactation
Trimethoprim should not be given to 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
Effects on ability to drive and use machines
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.
Blood and lymphatic system disorders
Leucopenia, megaloblastic anaemia, thrombocytopenia, agranulocyctosis,
hyperkalaemia (particularly in the elderly and in HIV patients),
methaemoglobinaemia. Trimethoprim therapy may affect haematopoiesis due
to interference in folic acid metabolism when given over a prolonged period.
This effect may be countered by intramuscular injections of calcium folinate.
Nervous system disorders
Nausea, vomiting, glossitis, gastrointestinal disturbances, sore mouth.
Disturbances in liver enzyme values, cholestatic jaundice.
Renal and urinary disorders
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.
Skin and subcutaneous tissue disorders
Pruritus, skin rashes, exfoliative dermatitis, urticaria. More severe skin
sensitivity or allergic reactions such as photosensitivity, angioedema,
erythema multiforme, Stevens Johnson syndrome and epidermal necrolysis
have been reported rarely.
Musculoskeletal system disorders
General disorders and administration site conditions
Anaphylactic and anaphylactoid reactions have been reported rarely, drug
Symptomatic treatment, gastric lavage and forced alkaline diuresis may be
used. Depression of haematopoiesis by trimethoprim may be countered with
intramuscular calcium folinate.
Pharmacotherapeutic group: Systemic antibacterial.
ATC Code: J01EA01
Mechanism of action: Trimethoprim is a dihydrofolate reductase inhibitor
which affects the nucleoprotein metabolism of micro-organisms by
interference in the folic-folinic acid systems. The antimicrobial spectrum of
Trimethoprim is similar to that of the sulphonamides, while sulphonamides
inhibit bacterial synthesis of dihydrofolic acid from p-aminobenzoic acid,
Trimethoprim inhibits dihydrofolate reductase and this prevents the synthesis
of tetrahydrofolic acid from dihydrofolic acid.
Trimethoprim is effective in vitro against a wide range of Gram-positive and
aerobic Gram-negative organisms, including enterobacteria Escherica coli,
Proteus, Klebsiella pneumoniae, Streptococcus pneumoniae, Streptococcus
faecalis, Haemophilus influenzae and Staphylococcus aureus.
It is not effective against Anaerobes, Pseudomonas aeruginosa, Treponema
pallidum, Mycobacteria, Nocardia species, Neisseria species and Brucella
Trimethoprim is rapidly and almost completely absorbed from the gastrointestinal tract and peak concentrations in the circulation occur about 1- 4
hours after an oral dose. Peak plasma concentrations of about 1 µg/ml have
been reported after a single dose of 100 mg. Approximately 40 - 70% is bound
to plasma proteins. Tissue concentrations are reported to be higher than serum
concentrations, with particularly high concentrations in the kidneys and lungs
but concentrations in the cerebrospinal fluid are about one-half of those in the
blood. The half-life is approximately 8 - 10 hours. About 40 to 60% of a dose
is excreted unchanged in the urine within 24 hours, together with metabolites;
hence, patients with impairment of renal function such as the elderly may
require a reduction in dosage due to accumulation. It appears in breast milk.
Pre-clinical Safety Data
List of excipients
Each tablet contains:
Sodium starch glycollate
Special precautions for storage
Store at room temperature, keep well closed, protect from light.
Nature and content of container
White polypropylene “tampertainer” tub with “Jaycap” security seal. Pack
sizes 14, 28, 30, 50, 100, 250, 500 and 1000 tablets.
Instructions for use and handling
MARKETING AUTHORISATION HOLDER
M & A Pharmachem Limited,
Bolton, BL5 2AL.
MARKETING AUTHORISATION NUMBER
DATE OF FIRST AUTHORISATION/RENEWAL OF THE
29/06/88, last renewed 11/09/97.
DATE OF REVISION OF THE TEXT
Source: Medicines and Healthcare Products Regulatory Agency
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