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6-(4-dimethylamino-3-hydroxy- 6-methyl-oxan-2-yl)oxy- 14-ethyl-7,12,13-trihydroxy-
4-(5-hydroxy-4-methoxy-4,6-dimethyl- oxan-2-yl)oxy-3,5,7,9,11,13-hexamethyl- 1-oxacyclotetradecane-2,10-dione
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Absorption
Orally administered erythromycin base and its salts are readily absorbed. Because of interindividual variation in absorption, some patients do not achieve optimal serum concentrations.
Distribution
Erythromycin diffuses into most body fluids. In the absence of meningeal inflammation, low concentrations are achieved in the spinal fluid; however, passage across the blood-brain barrier increases in meningitis. Although erythromycin crosses the placenta, fetal plasma levels are low. Erythromycin is extensively bound to plasma protein.
Elimination
Erythromycin is not removed by peritoneal dialysis. Erythromycin is concentrated in the liver and excreted in the bile. Less than 5% is recovered in the active form in the urine.
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Anticoagulants
May increase anticoagulant effects.
Bromocriptine
May increase serum bromocriptine levels.
Cisapride, pimozide
Plasma levels may be elevated, increasing the risk of life-threatening cardiac arrhythmia and torsades de pointes; coadministration with erythromycin is contraindicated.
Drugs inhibited by CYP3A metabolism (eg, alfentanil, buspirone, carbamazepine, cilostazol, cyclosporine, disopyramide, felodipine, HMG-CoA reductase inhibitors [eg, lovastatin, simvastatin]), phenytoin valproate, phosphodiesterase type 5 inhibitors [eg, sildenafil, tadalafil, vardenafil], quinidine, repaglinide, tacrolimus, theophyllines, triazolobenzodiazepines [eg, alprazolam, midazolam, triazolam], vinblastine)
Plasma levels may be elevated by erythromycin, increasing the pharmacologic effects and risk of toxicity (eg, rhabdomyolysis with lovastatin or simvastatin).
Clindamycin, topical
Antagonism may occur with topical erythromycin; coadministration is not recommended.
Digoxin
May cause increased digoxin levels.
Ergot derivative
Ergot toxicity may occur.
Grapefruit juice
May inhibit erythromycin metabolism, increasing plasma levels and adverse effects.
Methylprednisolone
May decrease Cl of methylprednisolone.
Quinolone antibiotics (eg, gatifloxacin, levofloxacin, moxifloxacin, sparfloxacin)
Risk of life-threatening cardiac arrhythmias, including torsades de pointes, may be increased.
Rifamycins (eg, rifabutin)
Rifabutin plasma levels may be increased while erythromycin levels and antibiotic activity may be decreased.
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