Effect of concomitant food intake on absorption kinetics of erythromycin in healthy volunteers

Food-drug interactions

Interactions between food and drugs may inadvertently reduce or increase the drug effect. The majority of clinically relevant food-drug interactions are caused by food-induced changes in the bioavailability of the drug. Since the bioavailability and clinical effect of most drugs are correlated, the bioavailability is an important pharmacokinetic effect parameter. However, in order to evaluate the clinical relevance of a food-drug interaction, the impact of food intake on the clinical effect of the drug has to be quantified as well. As a result of quality review in healthcare systems, healthcare providers are increasingly required to develop methods for identifying and preventing adverse food-drug interactions. In this review of original literature, we have tried to provide both pharmacokinetic and clinical effect parameters of clinically relevant food-drug interactions. The most important interactions are those associated with a high risk of treatment failure arising from a significantly reduced bioavailability in the fed state. Such interactions are frequently caused by chelation with components in food (as occurs with alendronic acid, clodronic acid, didanosine, etidronic acid, penicillamine and tetracycline) or dairy products (ciprofloxacin and norfloxacin), or by other direct interactions between the drug and certain food components (avitriptan, indinavir, itraconazole solution, levodopa, melphalan, mercaptopurine and perindopril). In addition, the physiological response to food intake, in particular gastric acid secretion, may reduce the bioavailability of certain drugs (ampicillin, azithromycin capsules, didanosine, erythromycin stearate or enteric coated, and isoniazid). For other drugs, concomitant food intake may result in an increase in drug bioavailability either because of a food-induced increase in drug solubility (albendazole, atovaquone, griseofulvin, isotretinoin, lovastatin, mefloquine, saquinavir and tacrolimus) or because of the secretion of gastric acid (itraconazole capsules) or bile (griseofulvin and halofantrine) in response to food intake. For most drugs, such an increase results in a desired increase in drug effect, but in others it may result in serious toxicity (halofantrine).

Effect of a high-fat meal on the bioavailability of a polymer-coated erythromycin particle tablet formulation

The effect of food on the relative bioavailability of an erythromycin particles-in-tablet formulation was studied in 27 healthy volunteers, using a four-way, crossover study design with the following treatments: one or two erythromycin capsules USP (Eryc, Parke-Davis), or one polymer-coated erythromycin particles-in-tablet (PCE, Abbott) administered fasting or with a high-fat meal. Under fasting conditions the erythromycin particles-in-tablet and erythromycin capsule formulations are bioequivalent based on similar tmax and dose-normalized Cmax and AUC values. The rate and extent of absorption from the particles-in-tablet formulation, however, are dramatically reduced following administration with a meal. Mean Cmax and AUC values decreased by 73% and 72%, respectively, and seven subjects had no detectable erythromycin plasma concentrations for 16 hours following administration of the particles-in-tablet formulation with the high-fat meal. Greater than 40% of the subjects had nonfasting Cmax and AUC values that were less than 10% of those values following administration of the dose fasting. Cmax and AUC values in nonfasting subjects were within 75% to 125% of fasting values in only two and one of 27 subjects, respectively. The erythromycin particles-in-tablet formulation therefore should not be administered with meals.

Pharmacokinetic advantages of erythromycin estolate over ethylsuccinate as determined by high-pressure liquid chromatography

The pharmacokinetics of erythromycin estolate (500 mg) and erythromycin ethylsuccinate (600 mg) were compared in 12 healthy volunteers after single doses and after repeated oral doses (every 8 h). High-pressure liquid chromatography with electrochemical detection was used to determine concentrations in plasma and urine of estolate, ethylsuccinate, and erythromycin base. The maximum concentration of drug in the serum, the half-life, and the area under the curve for erythromycin estolate were significantly greater than those of erythromycin ethylsuccinate after both regimens. After single and multiple doses, the respective areas under the curve of erythromycin base generated by estolate formulation were 3 and 1.6 times greater (P less than 0.05) than those of ethylsuccinate. The lower percentage of hydrolysis of erythromycin estolate (41 versus 69%) combined with its longer half-life (5.47 versus 2.72 h) and its larger area under the curve (30.61 versus 4.68 micrograms/h/ml, after multiple doses) could explain these differences. This study underscores the need for a specific high-pressure liquid chromatography assay and the importance of wide variability, rate-limited processes, changes with multiple doses, and the appearance of a second peak when one studies the pharmacokinetics of erythromycin esters. The pharmacokinetic data presented in this study reinforce the clinical advantages of erythromycin estolate over erythromycin ethylsuccinate.