Drug Interactions between amoxicillin / clarithromycin / lansoprazole and remdesivir

MONITOR: Coadministration with clarithromycin may increase the plasma concentrations of lansoprazole. The proposed mechanism is clarithromycin inhibition of intestinal (first-pass) and hepatic metabolism of lansoprazole via CYP450 3A4. Although lansoprazole is primarily metabolized by CYP450 2C19 in the liver, 3A4-mediated metabolism is the predominant pathway in individuals who are 2C19-deficient (approximately 3% to 5% of the Caucasian and 17% to 20% of the Asian population). Additionally, inhibition of P-glycoprotein intestinal efflux transporter by clarithromycin may also contribute to the interaction, resulting in increased bioavailability of lansoprazole. In 18 healthy volunteers--six each of homozygous extensive metabolizers (EMs), heterozygous EMs, and poor metabolizers (PMs) of CYP450 2C19--clarithromycin (400 mg orally twice a day for 6 days) increased the peak plasma concentration (Cmax) of a single 60 mg oral dose of lansoprazole by 1.47, 1.71- and 1.52-fold, respectively, and area under the concentration-time curve (AUC) by 1.55-, 1.74- and 1.80-fold, respectively, in each of these groups compared to placebo. The AUC ratio of lansoprazole to lansoprazole sulphone, which is considered an index of CYP450 3A4 activity, was significantly increased by clarithromycin in all three groups. However, elimination half-life of lansoprazole was prolonged by 1.54-fold only in PMs. Mild diarrhea was reported in two subjects and mild abdominal disturbance in six subjects during clarithromycin coadministration. These side effects continued until day 6 and ameliorated the day after discontinuation of clarithromycin, whereas no adverse events were reported during placebo administration or after lansoprazole plus placebo. In another study, clarithromycin induced dose-dependent increases in the plasma concentration of lansoprazole in a group of 20 patients receiving treatment for H. pylori eradication. Mean 3-hour plasma lansoprazole concentration was 385 ng/mL for the control subjects who received lansoprazole 30 mg and amoxicillin 750 mg twice a day for 7 days; 696 ng/mL for patients coadministered clarithromycin 200 mg twice a day; and 947 ng/mL for patients coadministered clarithromycin 400 mg twice a day.

MANAGEMENT: Although lansoprazole is generally well tolerated, caution may be advised during coadministration with clarithromycin, particularly if higher dosages of one or both drugs are used. Dosage adjustment may be necessary in patients who experience excessive adverse effects of lansoprazole.

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GENERALLY AVOID: Concomitant use of remdesivir with other agents that are known to induce hepatotoxicity may theoretically increase the risk of liver injury. Data from investigational use and clinical studies suggest that remdesivir may be associated with hepatotoxic effects. Transient treatment-emergent Grade 1 or Grade 2 elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were observed during multiple-dose Phase 1 studies in healthy volunteers. Some ALT and AST elevations were associated with graded PT elevations, but there were no graded changes in international normalized ratio (INR). Laboratory results for these subjects indicated no systemic sign of drug reaction. Liver transaminase elevations, including grade 3 or higher, were also observed in some participants during compassionate or investigational use of remdesivir and clinical studies for the treatment of COVID-19. The mechanism of potential hepatotoxicity is unknown and the contribution of remdesivir is difficult to determine, as transaminase elevations have also been reported as a component of COVID-19, including in patients receiving placebo in clinical trials of remdesivir.

MANAGEMENT: Until more information is available, concomitant use of remdesivir with known hepatotoxic drugs should be avoided when possible. Liver function should be evaluated prior to starting remdesivir and monitored during treatment as clinically appropriate. Remdesivir should not be initiated in patients with ALT greater than or equal to 5 times the upper limit of normal (ULN) at baseline. Likewise, remdesivir should be discontinued immediately if ALT increases to 5 times ULN or greater during treatment (may be restarted when ALT falls below 5 times ULN), or if ALT elevation is accompanied by signs or symptoms of liver inflammation or increasing conjugated bilirubin, alkaline phosphatase, or INR.

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Although some in vitro data indicate synergism between macrolide antibiotics and penicillins, other in vitro data indicate antagonism. When these drugs are given together, neither has predictable therapeutic efficacy. Data are available for erythromycin, although theoretically this interaction could occur with any macrolide. Except for monitoring of the effectiveness of antibiotic therapy, no special precautions appear to be necessary.

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