A Senior Clinical Pharmacist and member of the National Association of Hospital and Administrative Pharmacists of Nigeria, Ejionye Oluchi, discusses co-trimoxazole better known as septrin
What is co-trimoxazole?
Co-trimoxazole or septrin as you may call it is an antibiotic or specifically antibacterial formulation composed of two active constituents or drugs. The first is a sulfonamide antibiotic, sulfamethoxazole (SMZ), and the other is trimethoprim (TMP); sometimes abbreviated as SMZ-TMP. Both drugs belong to the class of antibiotics called antifolates. They are so called because they prevent the synthesis or utilisation of folic acid by the bacterial cell. They do this by inhibiting the enzymes in the bacteria that carry out such actions.
Folic acid is a vitamin used by both human and bacteria cells to produce some chemicals needed for DNA synthesis, which is the building block of our genetic makeup. Every living, developing or growing cell or organism needs an effective genetic functioning. That is why folic acid is a most for pregnant women. If the genetic functioning is prevented by blocking folic acid utilisation, the organism simply stops growing and ultimately dies.
Bacteria cells do not use exogenous folic acid, they synthesis their own. Hence, co-trimoxazole has much more effect on bacteria than on human cells. Simultaneous utilisation of the two drugs, SMZ-TMP, gives a good synergistic effect than when either drug is used independently.
Apart from all you stated above, what are the other uses of co-trimoxazole?
Co-trimoxazole is an antibacterial formulation and so is used to treat bacterial infections caused by susceptible organisms. Such infections include urinary tract infections, respiratory tract infections like infected bronchitis, pneumonia, infections in cystic fibrosis, otitis media and intra-abdominal infections such as typhoid fever.
However, it is not all bacteria that are susceptible to the drug. The right thing to do when you have any of such infections is to consult a clinician who will prescribe a microbial culture and sensitivity (MCS) test to ascertain what organism is responsible for the infection and to which antibiotic it is sensitive before prescribing such drug; though empirical treatment may commence while awaiting the test result.
Recently, co-trimoxazole (septrin) has been found to boost the immunity of HIV/AIDS patients, thereby improving their resistance to infections. The exact mechanism of this effect is not well known but the drug has become part of the routine therapy for such patients. Nevertheless, such use must be under the supervision of the attending clinician since the drug may interact with some antiretroviral agents.
On what health situations is co-trimoxazole not to be used?
This is a very important question because the drug is often misused. People use septrin as a routine cough regimen. Whenever parents or their wards manifest any symptom of cough, they quickly run to a “chemist” shop to pick either the tablet or suspension of septrin. This is a bad practice and has serious public health consequences.
Indiscriminate use of septrin and as a matter of fact any other antibiotic, may create enormous economic and health burden. Development of resistant strains of bacteria to these readily available and very affordable drugs is not an issue to be taken lightly. As we many know, resistant strains of bacteria has already started developing. Many infection cases are no longer responding to conventional treatment. The implication is that it is going to take huge investment of scarce resources in research, uncertain length of time with persistent hard-to-treat infections and much more, to develop alternatives to these cheap and available products. Such drugs will never be as affordable and available as septrin and other ones.
I must emphasise that cough has a variety of etiology. Cough may be due to allergic response, viral infection, mucus/fluid accumulation in the lungs/air ways, reaction to drugs and bacterial infections. When one has persistent cough after taking routine OTC demulcent, expectorant mucolytic cough preparation, visit your doctor or health professional for further diagnosis and proper treatment. Do not be in a haste to buy co-trimoxazole.
What are the side effects of co-trimoxazole?
Co-trimoxazole is a relatively safe drug and most of the side effects may not come through anyway. However, I will mention some of the important side effects.
Prolonged use of co-trimoxazole can cause liver problems and kidney problems especially if not taken with enough water or in a dehydrated or renal impaired patient as the drug can crystallise and accumulate in the kidneys. Other important adverse effects of septrin are hypersensitivity or allergic reactions which include rash, toxic epidermal necrosis, systematic lupus erythematosis and Stevens-Johnson syndrome. Although these reactions are rare, they usually have devastating effects when they occur. If you notice any form of rash or blister formation while or after taking this drug, please stop the drug immediately and report to the nearest health centre or facility near you. Co-trimoxazole can also cause some form of blood disorders especially in patients with already existing blood cell problems, ( for example sickle cell patients and those with G6PD deficiency).
Please state the drug interactions.
Co-trimoxazole interact with some drugs that may result in accumulation of the drug in the body (pharmacokinetic reactions), and thereby cause more adverse effects that may inhibit or potentiate the effect of the drug, (pharmacodynamic reactions). It is the responsibility of your pharmacist and doctor to inform you and possibly make some adjustments in your regimen. Tell your doctor or pharmacist if you are taking any of the following class of drugs as they may interact with septrin: drugs for rheumatism, anticancer drugs, drugs for hypertension, drugs for diabetes, drugs for epilepsy, drugs for HIV, drugs that affect blood clothing, and fansidar (sulfadoxin +/pyrimethamine) which is an antimalarial drug.
Is there any substitute for co-trimoxazole?
When it comes to management of bacterial infections, the term “substitute” is used carefully. Antibacterial therapy is all about susceptibility and safety. Substitution, if co-trimoxazole is contraindicated, will depend on a lot of factors, including the state of the patient, (for example pregnant, breast feeding, liver failure and kidney failure), bacteria species causing the infection and its sensitivity to test result, site of infection, (for example respiratory tract, urinary tract and intra-abdominal, central nervous system)
The expertise of a clinician is required in selecting a potential “substitute” for any medication. There are no hard and fast rules.
When should one not take co-trimoxazole?
A pregnant woman should not take septrin except under strict supervision of a doctor. As stated earlier, folic acid is a highly essential vitamin needed by a pregnant woman for neuronal development of the feotus and overall cell division and growth. Deficiency or malfunction of folic acid metabolism can lead to some teratogenic or other congenital abnormalities especially within the first trimester, (first 3 months of pregnancy). Co-trimoxazole is an antifolate and interferes with the body’s use of folic acid. It can also cause some blood related problems to the unborn baby when used within the last three months of pregnancy. This drug is better avoided during pregnancy or used under strict surveillance.
Patients with blood disorders like sickle cell anaemia should also not take septrin. Other conditions where the drug should be avoided or used with extra caution are: patients with renal impairment; patients with liver disorders; patients already sensitive to the drug (i.e. those that has reacted to it before), or to any other sulfurnamide such as some diuretics (drugs that make you urinate more), fansidar, some anti-diabetic drugs such as glibenclamide (also known as Daonil); and infants under six weeks.
What are the precautions to be taken?
Co-trimoxazole should be taken on empty stomach that is one hour before food or at least two hours after food. This is because food reduces the absorption of the drug from the stomach. Secondly, take septrin with at least a glass of water and plenty of water thereafter, and as long as the treatment goes. This is because the drug and its waste products are cleared or removed from the body through the kidney. These can easily crystalise within the kidney when there is reduced body fluid, especially if the urine is acidic. This can lead to serious kidney problems and later kidney failure. Finally, observe for signs of hypersensitivity reaction such as rash, blister formations, sore throat, difficulty breathing or swallowing fever, feeling like fainting. If you notice any of these, please stop the drug and call for medical attention.
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