Friday, May 25, 2007

Classes of Antibiotics

Penicillin’s: The first antibiotic drugs to be developed, penicillin’s are still widely used to treat many common infections. Some are not effective when they are taken by mouth and therefore have to be given by injection in the

hospital. Unfortunately, certain strains of bacteria are resistant to penicillin treatment, and other drugs may have to be substituted. Penicillin’s often cause allergic reactions.

Cephalosporins: These broad spectrum antibiotics, similar to the Penicillin’s, are often used when Penicillin treatment has proved ineffective. Some can be given by mouth, but others are only given by injection. About 10 per cent of people who are allergic to Penicillin’s are also allergic to Cephalosporin’s. Some Cephalosporin’s can occasionally damage the kidneys, particularly if used with amino glycosides. Another serious, although rare, adverse effect of a few Cephalosporins’ is that they occasionally interfere with normal blood clotting, leading to abnormally heavy bleeding, especially in the elderly.

Macrolides: Erythromycin is the most common drug in this group. It is a broad spectrum antibiotic that is often prescribed as an alternative to Penicillin’s or Cephalosporin’s. Erythromycin is also effective against certain diseases, such as Legionnaries' disease (a rare type of pneumonia), that cannot be treated with other antibiotics. The main risk with Erythromycin is that it can occasionally impair liver function.

Tetracyclines: These have a broader spectrum of activity than other classes of antibiotics. However, increasing bacterial resistance has limited their use, but they are still widely prescribed. As well as being used for the treatment of infections, Tetracyclines are also used in the long term treatment of acne, although this application is probably not related to their anti-bacterial action. A major drawback to the use of Tetracycline antibiotics in pregnant women and young children is that they are deposited in developing bones and teeth.

With the exception of Doxycycline, drugs from this group are poorly absorbed through the intestines and when given by mouth they have to be administered in high doses in order to reach effective levels in the blood. Such high doses increase the likelihood of diarrhea as a side effect. The

absorption of Tetracyclines can be further reduced by interaction with Calcium and other minerals. Drugs from this group should not therefore be taken with iron tablets or milk products. Tetracyclines deteriorate and may become poisonous with time, so leftover tablets or capsules should always be discarded.

Aminoglycosides: These potent drugs are effective against a wide range of bacteria. They are not as widely used as some other antibiotics since they have to be given by injection and have potentially serious side effects. Their use is therefore limited to hospital treatment of serious infections. They are often given with other antibiotics. Possible adverse effects include a severe skin rash and damage to the kidneys and nerves in the ear.

Lincosamides: The Lincosamide — Clindamycin — is not commonly used as it is more likely to cause serious disruption of bacterial activity in the bowel than other antibiotics. It is mainly reserved for the treatment of bone, joint, abdominal and pelvic infections that do not respond well to the safer antibiotics. Clindamycin is also used topically for acne and vaginal infections.

Quinolones: These drugs, often called anti-bacterials, are derived from chemicals rather than living organisms. Quinolones have a wide spectrum of activity. They are used in the treatment of urinary infections and are widely effective in acute diarrhoeal diseases, including that caused by salmonella, as well as in the treatment of enteric fever.

The absorption of Quinolones is reduced by antacids containing Magnesium and Aluminium. They are well tolerated but should be avoided by epileptics, as they may in rare cases cause convulsions, and by children, as studies have shown that they may cause arthritis.

How They Affect You

Antibiotics stop most common types of infection within days. Because they do not relieve symptoms directly, your doctor may advise additional medication, such as Analgesics, to relieve pain and fever until the antibiotics take effect.

It is important to complete the course of medication as prescribed by your doctor, even if all your symptoms have disappeared. Failure to do this can lead to a resurgence of the infection in an antibiotic-resistant form.

Most antibiotics used in the home do not cause adverse effects if taken in the recommended dosage. In people who do experience them, nausea and diarrhea are common. Some people may be sensitive to certain types of antibiotics, which can result in a variety of serious adverse effects.



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