Mediscene - Another infection buster

Another infection buster

In our series on commonly used drugs, this month we look at Sulfonamide + trimethoprim combinations (Cotrimoxazole).

By Melanie Amarasooriya

Cotrimoxazole is not widely prescribed these days; however, it is used to treat infections like bronchitis, middle ear infection, urinary tract infection and traveller's diarrhoea. Now trimethoprim alone is available which is mainly used for treatment and prevention of urinary tract infections. The general facts regarding use of antibacterial agents that have been discussed in the previous articles of this series are relevant to this group of drugs as well.

Proper use:

Cotrimoxazole is best taken with a full glass (8 ounces) of water. Several additional glasses of water should be taken every day, unless otherwise directed by your doctor. It should be taken twice a day. Trimethoprim is commonly given to infants and young children with some abnormalities in their renal (kidney) tract to prevent urinary tract infection which occurs more frequently in these children. For this indication, trimethoprim is given once in the night. It has to be continued until the doctors decide to stop, which is generally at the age of 5 years.

Allergy:

Although rare it is well known to cause serious allergic reactions. Therefore tell your doctor if you have ever had any unusual or allergic reaction to any of the sulfonamides or combination medicine containing a sulfonamide.

Pregnancy and breast feeding:

There are no reported harmful effects to the human foetus if the mother takes this drug during pregnancy. Nevertheless, it is contra-indicated in late pregnancy because it may cause unwanted effects in the baby. Cotrimoxazole passes into the breast milk; however it is safe if the baby is full term and healthy. Avoid if the baby is ill, preterm or jaundiced. Trimethoprim alone is safe to use.

Children:

This drug is known to cause unwanted effects so that it is best avoided in preterm infants and in infants less than 3 months of age unless specifically prescribed by a paediatrician. Never give your child this drug without a doctor prescribing it.

Drug interactions:

Like many other medicines, both cotrimoxazole and trimethoprim are also known to interact with other medicines. For example oral anti diabetic drugs, anti - epileptic drugs, anti - malarial drugs, warfarin, etc. If you are on this drug, seek advice from your doctor before taking other drugs (including over the counter preparations, cough medicines, herbal remedies, neutraceuticals). Hormonal contraceptive methods containing estrogen will not work effectively when you are taking this class of drugs. Hence, you need to switch to another method of contraception.

Other medical conditions:

The presence of other medical problems may affect the use of cotrimoxazole. Make sure you tell your doctor if you have any other medical problems, anaemia or other blood problems, Glucose-6-phosphate dehydrogenase (G6PD) deficiency, kidney disease, liver disease, or porphyria

Side effects:
* It may cause blood problems, especially if taken for a long time. Your doctor will ask you to monitor blood counts if necessary.

* Cotrimoxazole is known to cause a rare, but serious adverse reaction called Stevens Johnson Syndrome. It affects skin, mucus membrane and internal organs as well. So if a skin rash develops when someone is on this drug, he or she should stop the drug and report to the doctor.

* Other side effects include, aching of joints and muscles, difficulty in swallowing, pale skin, redness, blistering, peeling, or loosening of skin, sore throat and fever or unusual bleeding. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any continue or are bothersome.

Information provided by Dr. Shalini Sri Ranganathan (Senior Lecturer) and
Prof. Rohini Fernandopulle
Department of Pharmacology
Faculty of Medicine.

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