Dirithromycin

Dirithromycin

Dirithromycin is a macrolide glycopeptide antibiotic known for its distinctive prodrug formation. Commercially known as Dynabac, it stems from the modification of 9S-erythromycyclamine. Due to its specialized formation, dirithromycin demonstrates a unique mechanism of absorption and hydrolysis when administered orally.

Chemical Composition and Formation

Dirithromycin is derived from 9S-erythromycyclamine through a condensation process with 2-(2-methoxyethoxy)acetaldehyde. This results in the formation of a 9N, 11O-oxazine ring, an unstable hemi-aminal, which is susceptible to spontaneous hydrolysis under both acidic and alkaline conditions, leading to the formation of erythromycyclamine. This derivative, erythromycyclamine, is a semisynthetic adaptation of erythromycin wherein the 9-ketogroup of the erythronolide ring is transformed into an amino group. Impressively, erythromycyclamine maintains the antibacterial efficacy of its parent compound, erythromycin, upon oral administration.

Administration and Absorption

Dirithromycin is formulated as enteric-coated tablets to shield it from acid-mediated hydrolysis in the stomach. Upon oral ingestion, the prodrug is swiftly absorbed into the plasma, predominantly from the small intestine. Its spontaneous conversion to erythromycyclamine primarily occurs in the plasma. Despite its oral bioavailability being estimated at around 10%, food consumption does not impact the absorption of dirithromycin.

Discontinuation

As of recent developments, dirithromycin has been phased out and is no longer accessible in the United States. In light of this, the U.S. National Institutes of Health advises individuals currently on dirithromycin to engage their healthcare providers to discuss alternative therapeutic options.

See Also

• Macrolide
• Antibiotics
• Erythromycin