It is acid labile therefore given as enteric coated tablets. Food delays its absorption. It does not cross blood brain barrier. It is excreted primarily in the bile in active from.
INDICATIONS : First choice drug for mycoplasma pneumonia, hegionnaine's pneumonia and whooping cough. It is used a second choice drug for Campylobacter enteritis, chancroid, chlamydia trachomatis and penicillin resistant staphylococcal infections. It is used as an alternative to penicillin in penicillin allergic patient for streptococcal pharyngitis, tonsillitis, mastoiditis and diphtherial, tetnus, syphilis and gonorrhoea infection.
SAFETY PROFILE :Generally safe but should be carefully given in patients who are taking non sedative antihistaminics.
ADVERSE EFFECTS :Mild to severe epigastric pain, anorexia, nausea, vomiting, diarrhoea, reversible hearing impairment (very high dose), rash and fever hepatitis with cholestatic jaundice.
DRUG INTERACTIONS : By inhibiting cytochrome P450, it increases the serum concentration of theophylline, oral anticoagulants, cyclosporine and methylprednisolone. It increases serum concentration of oral digoxin by increasing its bioavailabilty. Erythromycin if administered with terfenadine/ astemizole/ cisapride causes ventricular arrhythmias.
DOSAGE :Adult: 250-500mg 3-4 times daily.Gonorrhoea : 500mg 6 hrly for 6-7 days. Syphillis: 1gm 6 hrly for 10-15 days. Prophylaxis against streptococci: 250mg 12 hrly. Children : 30-50mg/kg/24 day in divided doses.