Saturday, December 03, 2005



Lincomycin, And Clindamycin

Azithromycin Clarithromycin Clindamycin Erythromycin Lincomycin

The macrolides are similar in structure and activity. All the macrolides, lincomycin, and clindamycin are absorbed when taken orally, and erythromycin, lincomycin, azithromycin, and clindamycin can also be given parenterally. All are primarily bacteriostatic and bind to the 50S subunit of the ribosome, thus inhibiting bacterial protein synthesis. These drugs are active against aerobic and anaerobic gram-positive cocci, with the exception of enterococci, and against gram-negative anaerobes.


After oral or parenteral administration, these drugs diffuse well into body fluids, except CSF. Excretion is mainly in the bile, and dose adjustments are not required when renal failure is present.


Erythromycin is active against gram-positive cocci (including anaerobes), with the exception of enterococci; but many Staphylococcus aureus strains are now resistant and it should not be used in serious S. aureus infection. Erythromycin is also active against Mycoplasma pneumoniae, Chlamydia trachomatis, Chlamydia pneumoniae, Legionella pneumophila and other Legionella sp, Corynebacterium diphtheriae, Campylobacter, Treponema pallidum, and Borrelia burgdorferi. Erythromycin has been considered the substitute of choice in group A streptococcal and pneumococcal infections when penicillin cannot be used. However, pneumococci that are resistant to penicillin are often resistant to erythromycin. It should not be used to treat meningitis. It is the drug of choice in M. pneumoniae and Legionella infection, in C. diphtheriae carriers, and in Bordetella pertussis. Although it has activity against anaerobic gram-negative bacilli, its activity is much less than that of clindamycin. Erythromycin has been used orally in combination with an oral aminoglycoside for bowel preparation before GI tract surgery. Because of GI intolerance to erythromycin, clarithromycin and azithromycin are often used as substitutes, although they are much more expensive.

Clarithromycin and azithromycin have an antibacterial spectrum similar to that of erythromycin. In addition, they have enhanced activity against Haemophilus influenzae and activity against Mycobacterium avium-intracellulare. Azithromycin is used in a single dose for C. trachomatis urethritis and cervicitis. Clarithromycin has a half-life in serum of 4.7 h (3 times that of erythromycin), and azithromycin has a much longer half-life.

Clindamycin has a spectrum similar to that of erythromycin, except that it has poor activity against Mycoplasma. The major advantage of clindamycin over erythromycin is its much greater activity against anaerobic bacteria, especially Bacteroides sp (including B. fragilis). It also has activity against toxoplasma and pneumocystis when used in combination with other drugs. Clindamycin cannot be used in CNS infection because penetration into the brain and CSF is poor.

Lincomycin has a spectrum similar to that of clindamycin, but it is less active and is not as well absorbed after oral intake. Therefore, clindamycin is preferable.

Adverse Reactions

Erythromycin commonly causes dose-related GI tract disturbances, including nausea, vomiting, and diarrhea. These adverse effects are less common with clarithromycin and azithromycin. Cholestatic jaundice occurs with erythromycin estolate and less often with erythromycin ethylsuccinate. The jaundice usually appears after 10 days of administration, primarily in adults, but can occur earlier if the drug has been given previously. Erythromycin is not given IM because of severe pain; it may cause phlebitis when used IV. Hypersensitivity reactions are rare. Transient auditory impairment has rarely been noted with IV use of erythromycin or large oral doses of the estolate. Erythromycin raises blood levels of theophylline and potentiates terfenadine in producing ventricular arrhythmias. Clarithromycin may have similar effects. Clindamycin and lincomycin can cause diarrhea, which is sometimes severe.

Pseudomembranous colitis (caused by Clostridium difficile) and hypersensitivity reactions may occur.

Administration and Dosage

Erythromycin base, estolate, ethylsuccinate, and stearate can all be given orally in adult dosages of 250 mg to 1 g q 6 h. The dosage in children is 30 to 50 mg/kg/day in divided doses q 6 to 8 h. IV therapy is rarely required, but when necessary (as in severe Legionnaire's disease), continuous infusion is preferred; however, intermittent infusion (over 20 to 60 min) at intervals not more than q 6 h is also effective. Erythromycin lactobionate and gluceptate are used IV in dosages of 15 to 20 mg/kg/day in 4 divided doses (20 to 40 mg/kg/day in children). Up to 4 g/day have been used in very severe infections in adults.

Clarithromycin is used orally in a dose of 250 to 500 mg every 12 h in adults and 7.5 mg/kg every 12 h in children.

Azithromycin is used orally in adults in an initial single dose of 500 mg followed by 250-mg single daily doses on days 2 to 5 (or for children, 10 mg/kg followed by 5 mg/kg on days 2 to 5). A single 1-g dose is used in adults for chlamydial urethritis or cervicitis. An IV preparation is used in a dose of 500 mg/day as a replacement for oral therapy.

Clindamycin is used orally in dosages of 150 to 450 mg q 6 h in adults and 10 to 30 mg/kg/day in 3 to 4 divided doses in children. The IM or IV dosage is 600 to 2700 mg/day in 3 to 4 equal doses in adults and 20 to 40 mg/kg/day in 3 or 4 equal doses in children.

Lincomycin is used orally in dosages of 500 mg q 6 to 8 h in adults and 30 to 60 mg/kg/day in divided doses q 8 h in children. The IM or IV dosage is 600 mg q 8 h in adults and 10 to 20 mg/kg/day in divided doses q 8 h in children.




How It Works

Macrolides prevent bacteria from reproducing. (back to top)

Why It Is Used

Macrolides often are used to treat pneumonia in otherwise healthy people under age 60. For these people, macrolides are effective against the most common causes of bacterial infections in the lower respiratory tract.

Macrolides may be given to people who are allergic to penicillin.

Macrolides are used in people over age 60 and those with other long-term (chronic) health problems if an uncommon cause of pneumonia is suspected. 1 (back to top)

How Well It Works

Macrolides are effective against a wide range of bacteria. Erythromycin is effective against Legionella pneumophila.

Some improvement in symptoms is usually seen within 2 to 3 days after treatment is begun with a macrolide antibiotic. Unless the person gets worse during that time, treatment is not changed for at least 3 days. Antibiotics usually are continued for 7 to 14 days. Treatment may be longer for people with impaired immune systems or who have Legionnaires' disease.

Side Effects

The most common side effects of macrolides include:

Upset stomach.
Sore mouth.

A recent large study indicates that people who take erythromycin along with certain common medications may increase their risk of sudden cardiac death. 2 The study showed that the risk of sudden cardiac death is greater when erythromycin is taken with some medications that inhibit certain liver enzymes—such as certain calcium-channel blockers, certain antifungal medications, and some antidepressants—than when these medications are not taken together.

What To Think About

Clarithromycin and azithromycin are more expensive than erythromycin, but both are effective against a wide range of bacteria and have fewer side effects. They may replace erythromycin when treating people who have pneumonia who also have other health problems or are over age 60. Clarithromycin and azithromycin may be the best choice for people who:

Cannot take erythromycin.
Are more likely to have pneumonia caused by Haemophilus influenzae.
All the macrolide antibiotics are effective against lower respiratory tract infections caused by Legionella pneumophila, which also causes Legionnaires' disease.
Because azithromycin is long-acting, it is usually given for only 5 days when treating bronchitis or pneumonia.


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