See also the following individual entries:

Erythromycin base Erythromycin estolate Erythromycin ethylsuccinate Erythromycin lactobionate Erythromycin stearate Action/Kinetics: Erythromycins are considered to be macrolide antibiotics. They inhibit protein synthesis of microorganisms by binding reversibly to a ribosomal subunit (50S), thus interfering with the transmission of genetic information and inhibiting protein synthesis. The drugs are effective only against rapidly multiplying organisms. Absorbed from the upper part of the small intestine. Those for PO use are manufactured in enteric-coated or film-coated forms to prevent destruction by gastric acid. Erythromycin is approximately 70% bound to plasma proteins and achieves concentrations in body tissues about 40% of those in the plasma. Diffuses into body tissues; peritoneal, pleural, ascitic, and amniotic fluids; saliva; through the placental circulation; and across the mucous membrane of the tracheobronchial tree. Diffuses poorly into spinal fluid, although penetration is increased in meningitis. Alkalinization of the urine (to pH 8.5) increases the gram-

negative antibacterial action. Peak serum levels: PO, 1-4 hr. tv2: 1.5—2

hr, but prolonged in clients with renal impairment. Partially metabolized by the liver and primarily excreted in bile. Also excreted in breast milk. Uses

1. Upper respiratory tract infections due to Streptococcus pyogenes (group a beta-hemolytic streptococci), Streptococcus pneumoniae, and Haemophilus influenzae (combined with sulfonamides).

2. Mild to moderate lower respiratory tract infections due to S. pyogenes and S. pneumoniae. Respiratory tract infections due to Mycoplasma pneu-moniae.

3. Pertussis (whooping cough) caused by Bordetella pertussis; may also be used as prophylaxis of pertussis in exposed individuals.

4. Mild to moderate skin and skin structure infections due to S. pyo-genes and Staphylococcus aureus.

5. As an adjunct to antitoxin in diphtheria (caused by Corynebacteri-um diphtheriae), to prevent carriers, and to eradicate the organism in carriers.

6. Intestinal amebiasis due to Entamoeba histolytica (PO erythromycin only).

7. Acute pelvic inflammatory disease due to Neisseria gonorrhoeae.

8. Erythrasma due to Corynebacteri-um minutissimum.

9. Chlamydia trachomatis infections causing urogenital infections during pregnancy, conjunctivitis in the newborn, or pneumonia during infancy. Also, uncomplicated chla-mydial infections of the urethra, en-docervix, or rectum in adults (when tetracyclines are contraindicated or not tolerated).

10. Nongonococcal urethritis caused by Ureaplasma urealyticum when tetracyclines are contraindicated or not tolerated.

11. Legionnaires' disease due to Legionella pneumophilia.

12. As an alternative to penicillin (in penicillin-sensitive clients) to treat primary syphilis caused by Treponema pallidum.

13. Prophylaxis of initial or recurrent attacks of rheumatic fever in clients allergic to penicillin or sulfona-mides.

14. Infections due to Listeria monocy-togenes.

15. Bacterial endocarditis due to al-pha-hemolytic streptococci, Viridans group, in clients allergic to penicillins.

Non-FDA Approved: Infections due to N. gonorrhoeae, including uncomplicated urethral, rectal, or en-docervical infections and disseminated gonococcal infections (including use in pregnancy). Severe or prolonged diarrhea due to Campylo-bacter jejuni. Genital, inguinal, or anorectal infections due to Lymphog-ranuloma venereum. Chancroid due to Haemophilus ducreyi. Primary, secondary, or early latent syphilis due to T. pallidum. Erythromycin base used with PO neomycin prior to elective colorectal surgery to reduce wound complications. As an alternative to penicillin to treat anthrax, Vincent's gingivitis, erysipeloid, ac-tinomycosis, tetanus, with a sulfona-mide to treat Nocardia infections, infections due to Eikenella corro-dens, and Borrelia infections (including early Lyme disease). Contraindications: Hypersensitiv-ity to erythromycin; in utero syphilis. Special Concerns: Use with caution in liver disease and during lactation. Use may result in bacterial and fungal overgrowth (i.e., superinfection).

Side Effects: Erythromycins have a low incidence of side effects (except for the estolate salt). GI (most common): N&V, diarrhea, cramping, abdominal pain, stomatitis, anorexia, melena, heartburn, pruritus ani, pseudomembranous colitis. Allergic: Skin rashes with or without pruritus, bullous fixed eruptions, urticaria, eczema, anaphylaxis (rare). CNS: Fear, confusion, altered thinking, uncontrollable crying or hysterical laughter, feeling of impending loss of consciousness. CV: Rarely, ventricular arrhythmias, including ventricular tachycardia and torsades de pointes in clients with prolonged QT intervals.

Miscellaneous: Superinfection, he-patotoxicity, ototoxicity. Following topical use: Itching, burning, irritation, or stinging of skin. Dry, scaly skin.

IV use may result in venous irritation and thrombophlebitis; IM use produces pain at the injection site, with development of necrosis or sterile abscesses. Drug Interactions Alfentanil / l Excretion of alfentanil ^ T effect

Astemizole / Serious CV side effects, including torsades de pointes and other ventricular arrhythmias (including QT interval prolongation), cardiac arrest, and death Carbamazepine / T Effect (and tox-icity requiring hospitalization and resuscitation) of carbamazepine due to l breakdown by liver Lincosamides / Drugs antagonize each other

Methylprednisolone / T Effect of methylprednisolone due to l breakdown by liver

Penicillin / Erythromycins either l or T effect of penicillins Sodium bicarbonate / T Effect of erythromycin in urine due to alka-linization

Terfenadine / Serious CV side effects, including torsades de pointes and other ventricular arrhythmias (including QT interval prolongation), cardiac arrest, and death Triazolam / T Bioavailability of triazolam ^ T CNS depression

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