Catherine Langan, Françoise Van Bambeke

Clarithromycin

In: KUCERS' THE USE OF ANTIBIOTICS: A CLINICAL REVIEW OF ANTIBACTERIAL,
ANTIFUNGAL, ANTIPARASITIC AND ANTIVIRAL DRUGS
6TH EDITION

VO·LUME 1, pages 779-800

2010 Edward Arnold (Publishers) Ltd,

Clarithromycin (CAS number: 81103~11~9) is the 6-0-methyl
derivative of erythromycin (Morimoto et al., 1984; Fernandes et al.,
1986). The replacement of the hydroxyl substituant by a methoxy
group in position 6 renders the molecule resistant to acidic hydrolysis
improving its oral bioavailability compared with erythromycin (see
Chapter 59, Erythromycin). The empirical formula is C3SH69N013 and
the molecular weight is 748.0; the molecular structure is shown in
Figure 61.1.

In general, clarithromycin has the same spectrum and the same
therapeutic indications as erythromycin (Amsden, 1996). The in vitro
activity of clarithromycin against most aerobic microorganisms is equal
to or twice that of erythromycin, except for Haemophilus injluenzae for
which it is half as active (Fernandes et al., 1986; Hardy et al., 1988a).
Owing to its high intrinsic activity, it is the macrolide of choice for
Helicobacter pylori gastritis and Mycobacterium avium complex (MAC)
infection. Moreover, it is associated with an improved pharmacokinetic
profile - higher oral bioavailability, -loiiger half-life, higher tissue
accumulation, and lower degree of interaction with CYP450 (Periti
et al., 1992; Fraschini et al., 1993). Jn humans, clarithromycin has four
metabolites, the most important of which is 14-hydroxy clarithromycin.
This metabolite shows antimicrobial activity with MICs usually
one or two dilutions lower than those of clarithromycin (Logan et al.,
1991; Martin et al., 2001).