Someone asked about Zithromax, a macrolide erythromycin-like antibiotic.
Below is a recent reference.


Tom Hale

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Azithromycin            Fax # 1032

Trade:  Zithromax
Uses:   Erythromycin-like antibiotic
AAP:    Not reviewed

Azithromycin belongs to the erythromycin family.  Extremely long half-life
particularly in tissues.  Azithromycin is concentrated for long periods in
phagocytes which are known to be present in human milk.  In one study of a
patient who received 1 gm initially, followed by two  500mg doses at 24 hr
intervals,  the concentration of azithromycin in breastmilk varied from
0.64 mg/L (initially) to 2.8 mg/L on day 3. The predicted dose of
azithromycin received by the infant would be approximately 0.482 mg/day
(assuming milk volume of 150 mL/day and 37% bioavailability).   This would
suggest that the level of azithromycin ingested by a breastfeeding infant
is not clinically significant.  New pediatric formulations of azithromycin
have been recently introduced.   Pediatric dosing is 10 mg/kg STAT,
followed by 5 mg/kg per day for up to 5 days.

Adverse Effects: Diarrhea, loose stools, abdominal pain, vomiting, nausea

AHL= 48-68 hours         M/P=
PHL=                     PB  = 7-51%
PK  = 3-4 hours          Oral= 37%

References:
1.      Pharmaceutical Manufacturers Package Insert, 1996.
2.      Kelsey JJ, Moser LR, Jennings JC, et.al. Presence of azithromycin
breast milk concentrations: A case report. Am. J. Obstet. Gynecol.
170:1375-6,

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