Co-Trimoxazole
Brand names Bactrim, Chemotrim, Comixco, Fectrim, Laratrim, Septrin
Used in the following combined preparations (Co-trimoxazole is a combination of
trimethoprim and sulphamethoxazole)
GENERAL INFORMATION
Co-trimoxazole is a mixture of two antibacterial drugs in the ratio of one part trimethoprim and five parts sulphamethoxazole. It is prescribed for some serious respiratory and urinary tract infections that cannot be treated with other drugs. Co-trimoxazole is also used to treat Pneumocystis pneumonia, and may be
used for otitis media in children if no safer drug is suitable. Although co-trimoxazole was widely prescribed in the past, its use has now greatly declined with the introduction of new, more effective, and safer drugs.
The side effects of co-trimoxazole are a combination of those caused by the antibacterial drugs it contains and include nausea, vomiting, rash, sore tongue, and rarely jaundice, serious skin or blood disorders, and serious liver or
kidney damage.
INFORMATION FOR USERS
Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.
How taken
Tablets, liquid, injection.
Frequency and timing of doses
Normally 2 x daily, preferably with food.
Adult dosage range
Usually 4-6 tablets daily (each standard tablet is 480mg). Higher doses are required for the treatment of Pneumocystis pneumonia.
Onset of effect
1-4 hours.
Duration of action
12 hours.
Diet advice
Drink plenty of fluids, particularly in warm weather.
Storage
Keep in a closed container in a cool, dry place out of the reach of children.
Protect from light.
Missed dose
Take as soon as you remember. If your next dose is due at this time, double the usual dose to make up the missed dose.
Stopping the drug
Take the full course. Even if you feel better, the original infection may still be present and symptoms may recur if treatment is stopped too soon.
Exceeding the dose
An occasional unintentional extra dose is unlikely to be a cause for concern.
Large overdoses may cause nausea, vomiting, dizziness, and confusion. Notify your doctor.
POSSIBLE ADVERSE EFFECTS
Side effects can be caused by either the trimethoprim or the sulphamethoxazole ingredient of this preparation. The most common problems are nausea and rash.
INTERACTIONS
Warfarin Co-trimoxazole may increase its anticoagulant effect; the dose of warfarin may have to be reduced.
Phenytoin Co-trimoxazole may cause a build-up of Phenytoin in the body; the dose of Phenytoin may have to be reduced.
Oral antidiabetic drugs Co-trimoxazole may increase the blood sugar lowering effect of these drugs.
Cyclosporin Taking cyclosporin with co-trimoxazole can impair kidney function.
QUICK REFERENCE
Drug group Antibacterial drug
Overdose danger rating Medium
Dependence rating Low
Prescription needed Yes
Available as generic Yes
SPECIAL PRECAUTIONS
Be sure to tell your doctor if:
You have long-term liver or kidney problems.
You have a blood disorder.
You have glucose-6-phosphate
dehydrogenase (G6PD) deficiency. You are allergic to sulphonamide drugs.
You suffer from porphyria.
You are taking other medications.
Pregnancy
Not usually prescribed. May cause defects in the baby. Discuss with your doctor.
Breast-feeding
The drug passes into the breast milk, but at normal levels adverse effects on the baby are unlikely. Discuss with your doctor.
Infants and children
Not recommended in infants under 6 weeks old. Reduced dose necessary in older
children.
Over 60
Side effects are more likely. Used only when necessary, and often in reduced dosage.
Driving and hazardous work
No known problems.
Alcohol
No known problems.
PROLONGED USE
Long-term use of this drug may lead to folic acid deficiency which, in turn, can cause a blood abnormality. Folic acid supplements may be prescribed.
Monitoring Periodic blood tests to monitor blood composition are usually carried
out.
