Cotrimoxazole is a combination of two antibiotics. Its formulation is made up of five parts sulfamethoxazole and one part trimethoprim. This combination has a synergistic antibacterial effect. It is used to treat the simplest to the most advanced bacterial infections.
Cotrimoxazole IUPAC name is 5-[(3,4,5-trimethoxyphenyl)methyl]pyrimidine-2,4-diamine and has a molecular formula of C14H18N4O3. It is almost completely absorbed by mouth and will take effect within 1 to 4 hours.
Bacteria that are often killed by cotrimoxazole depend on dihydropteroic acid and tetrahydrofolic acid to produce folic acid for survival. Folic acid is used by bacteria to create genetic material. Sulfamethoxazole is similar to para-aminobenzoic acid, which prevents production of dihyropteroic acid. Trimethoprim diminishes the production of bacterial enzyme dihydrofolate reductase, which inhibits tetrahydrofolic acid.
Uses and common dosages
Cotrimoxazole is prescribed for pneumocystic pneumonia, chronic bronchitis, urinary tract infection, acute ear infections in children, skin or wound infections, infections in the gastrointestinal tract, shigellosis, traveler’s diarrhea. Whipple's disease, cerebral toxoplasmosis in HIV patients, and melioidosis.
|Contraindications||For adults||For children|
| For susceptible infections,
urinary tract infections,
gastrointestinal tract infections,
and respiratory tract infections.
| 960 milligrams twice daily
in 2 divided doses, in severe cases.
This must not exceed 2.88 grams a day.
| 6 weeks to 5 months - 120 milligrams twice daily |
6 months to 5 years - 240 milligrams twice a day
6 years to 12 years - 480 milligrams twice a day
| Prophylaxis of receptive infections
in AIDS patients
| May have a maximum dose
of 960 milligrams a day.
| 450 milligrams per square meter twice a day|
for three days in each week. This may be given
consecutively or in alternate days.
Total dose per day must not exceed 960 milligrams.
Dose adjustment applies to those with renal and hepatic impairment. When under this medication, drinking plenty of water will prevent kidney stone formation.
When using cotrimoxazole, expect the following:
- Loss of appetite
- Stomach upset (nausea, vomiting)
Meanwhile, seek medical supervision immediately when these side effects develop with continuous use:
- Blood disorders (i.e. anemia)
- Allergic reactions
- Circulatory problems (i.e. bluish lips or fingernails)
- Breathing difficulties
- Heart dysfunction (i.e. palpitations, arrhythmia)
- Flu-like symptoms (fever, fatigue, chills, joint and muscle pain)
- Skin discomfort (i.e. sensitivity to light, redness or blistering)
- Jaundice or paleness
- Mouth sores
- Sore throat
Precautions and contraindications
Patients with with certain blood conditions such as neutropenia, agranulocystosis, aplastic or megalobastic anemia, and thrombocytopenia MUST NOT take cotrimoxazole.
Doctors will prescribe the drug with extreme caution in people with the following conditions:
- History of liver or kidney disease
- High levels of potassium in the blood
- G6PD (Glucose-6-phosphate) deficiency
This antibiotic might also affect other medications such as the following:
- Cyclosporin – May increase kidney damage.
- Phenytoin and pyrimethamine - May decrease levels of folic acid in the blood.
- Warfarin and nicoumalone – May increased blood thinning effects.
- Sulfonylureas – May decreased blood sugar levels.
- Oral contraceptives – May decrease effectiveness of the pill.
- Amiodarone - May cause eventual development of disturbed heart rhythms.
- Lamivudine and zalcitabine – May increase blood levels and toxic effects of these anti-viral drugs.
In some countries, cotrimoxazole is sold as over-the-counter medication. In the Philippines however, this drug requires a prescription. It is given for specialized infections to prevent bacterial tolerance to the drug.
Cotrimixazole is available as a suspension, syrup, capsules, or tablet in local pharmacies although internationally, parenteral preparations are available especially for patients with HIV. Popular brands are Bactrim ® and Septrim ® although generic versions are available.
Standard tablets or capsule products contain 400 milligram sulfamethoxazole and 80 milligrams trimethoprim. Fortified tablet or capsule formulations contain 800 milligrams sulfamethoxazole plus 160 milligrams trimethoprim. Suspensions 5 milliliters contain 400 milligrams sulfamethoxazole with 80 milligrams. Lastly, syrups contain 200 milligrams sulfamethoxazole to 40 milligrams of trimethoprim.
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