Dirithromycin

Oral
Pulmonary infections, Skin and soft tissue infections

Hypersensitivity. Patients who previously developed liver disorders while receiving the drug.

Hepatic or renal impairment; prolongation of QT interval; porphyria; pregnancy; lactation.

GI disturbances; hypersensitivity reactions; reversible hearing loss; cholestatic jaundice; CV effects; myasthenia-like syndrome; Stevens-Johnson syndrome; toxic epidermal necrolysis.

Drugs known to prolong QT interval; digoxin; oral contraceptives; cimetidine.
Potentially Fatal: Ventricular arrhythmias with astemizole, terfenadine and cisapride.

May interfere with measurements of urinary catecholamines A-hydroxycorticosteroids. False elevation of serum AST values when measured colorimetrically.

Description: Dirithromycin is a prodrug of erythromyclamine, which binds reversibly to 50s ribosomal subunit causing blockade of transpeptidation/translocation reactions, inhibition of protein synthesis and thus inhibition of cell growth. Spectrum of activity includes many gram-positive and some gram-negative bacteria, as well as mycoplasmas, spirochetes, chlamydias and rickettsias.
Pharmacokinetics:
Absorption: Readily absorbed after oral admin; undergoes rapid non-enzymatic hydrolysis to its active metabolite erythromycylamine. Bioavailability: About 10%.
Distribution: Widely distributed and tissue concentrations exceed those in plasma. Protein binding:15-30%.
Excretion: Largely excreted unchanged in the bile with only about 2% in the urine. Mean plasma half-life: About 8 hr.

Macrolides