Macrolide Antibiotics

Macrolide antibiotics are used to combat gram-positive and gram-negative bacteria. As you'll recall from microbiology, the gram stain is used as a method to identify a bacteria. If after staining, the bacteria it appears purple, then the bacteria are said to be gram positive. If it is pink, then the bacteria are gramnegative. There is one exception: If the bacteria are either purple or pink, then a macrobide antibiotic is effective against the bacteria.

The exception is with troleandomycin, which is a macrolide antibiotic. Troleandomycin is used to fight Streptococcus pneumoniae and Streptococcuus pyogenes.

Macrolide antibiotics are bacteriostatic. That is, they inhibit reproduction of bacteria, but do not kill the bacteria. By inhibiting reproduction, macrolide antibiotics control the bacterial growth giving the body's own immune system— or other medication—time to kill the bacteria.

Prescribers give patients macrolide antibiotics to fight soft tissue infections, skin infections, and infections of the respiratory and gastrointestinal tract.

Macrolides antibiotics have some side effects that adversely affect the patient. The most common side effects are nausea, vomiting, stomach pain, and cramps. These occur with azithromycin, clarithromycin, erythromycin, and dirithromycin. Troleandomycin causes stomach cramps and discomfort.

Before administering macrolides, the patient is assessed using the same techniques as described for other antibiotics. However, caution must be used when prescribing macrolides to patients who have liver disease. Those with a history of cardiac arrhythmias should not take erythromycin.

The patient should be advised to take macrolides with a full glass of water either an hour before meals or two hours after meals to avoid gastric distress. Some patients are intolerant to some marcrolides when taken orally. In these cases, enteric-coated or delayed-release capsules are appropriate to prescribe.

If marcolides are administered IV, they must be diluted in 100 to 200 mL of 0.9% NS solution or 5% dextrose solution (D5W) and infused over a period of 20 to 60 minutes.

The patient should be provided with the same instructions as those given to a patient who is receiving penicillin (see Penicillin and Patient Education).

Macrolide Antibiotics

Pregnancy Category: B




Erythromycin (E-Mycin, Erythrocin, Erythrocin


Protein-Binding: 65%

Half-Life: PO 1-2 hours; IV 3-5 hours


250-500 mg

Every 6 hours


1-4 g/d

Divided doses

Azithromyzin (Zithromax)

Protein-Binding: 50%

Half-Life: 11-55 hours


500 mg

First Day

250 mg

Daily thereafter

Clarithromycin (Biaxin)

Protein-Binding: 65%-75%

Half-Life: 3-6 hours

Pregnancy Category: C


250-500 mg

Every 12 hours

Erythromycin, dirithromycin (Dynabac)

Protein-Binding: Unknown

Half-Life: 20-50 hours

Pregnancy Category: C


250 mg (Erythromycin)

Every 6 hours

500 mg (dirithromycin)

Once a day


250-500 mg

Every 6 hours

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