Roxithromycin

Roxithromycin is a semisynthetic macrolide antibiotic. It is used to treat infections of the respiratory tract, urinary tract, and soft tissues. Roxithromycin is derived from erythromycin and has an almost identical structure. Roxithromycin is most effective against certain Gram-negative bacteria, particularly Legionella pneumophila. It is also currently being tested in clinical trials for the treatment of male pattern hair loss. It is taken by mouth.

Pharmacodynamics

Roxithromycin prevents the growth of bacteria by interfering with their protein synthesis. Roxithromycin binds to the 50S subunit of the bacterial ribosome, inhibiting the synthesis of peptides. This prevents the bacteria from multiplying and dividing.

Pharmacokinetics

Roxithromycin is absorbed very rapidly in the intestine and is 96% bound to plasma proteins in the blood. Roxithromycin is only partially metabolized in the liver, and more than half of the parent compound is excreted unchanged. The elimination half-life is approximately 12 hours.

Drug Interactions

• When combined with statins, there is a risk of serious side effects such as myopathy and rabdomyolysis.
• When Roxithromycin is combined with other antibiotics, cross-resistance may develop. These include primarily lincosamides, clindamycin, and chloramphenicol.
• Plasma levels of carbamazepine, theophylline, digoxin, and valproic acid may be increased when combined, resulting in a higher risk of adverse reactions.
• Terfenadine, astemizole, and cisapride may cause life-threatening cardiac arrhythmias when taken concomitantly.
• Methylprednisolone, triazolam, midazolam, alfentanil, felodipine, and coumarin-type anticoagulants may be metabolized more slowly, increasing duration and potency of action.

Side effects

The most common side effects are gastrointestinal;

• diarrhea
• Nausea
• Abdominal pain
• Vomiting

Less common side effects include central or peripheral nervous system events such as headache, dizziness, vertigo and also the rarely seen skin rashes, abnormal liver function values and alteration of the sense of smell and taste.

Toxicological Data

LD50 (rat, oral): 830 mg-kg-1