Drug Interactions between estradiol topical and ombitasvir / paritaprevir / ritonavir

MONITOR CLOSELY: Theoretical concerns exist that coadministration of estrogen-containing products may increase the risk of liver enzyme elevations associated with the use of ombitasvir/paritaprevir/ritonavir, with or without dasabuvir. The proposed mechanism is the inhibition of UDP-glucuronosyltransferase (UGT) by ombitasvir, paritaprevir, and dasabuvir. During clinical trials, approximately 1% of all subjects experienced post-baseline serum ALT levels greater than 5 times the upper limit of normal (ULN) after starting treatment, with or without ribavirin. The incidence increased to 25% (4/16) among women taking a concomitant medication containing ethinyl estradiol. Although the incidence of clinically relevant ALT elevations among women using estrogens other than ethinyl estradiol, such as estradiol and conjugated estrogens used in hormone replacement therapy, was just 3% (2/59), a similarly increased risk cannot be ruled out due to the limited number of subjects taking these other estrogens. In general, ALT elevations were asymptomatic, occurred during the first 4 weeks of treatment (mean 20 days; range 8 to 57 days), and declined within two to eight weeks of onset despite continued therapy. Elevations in ALT were typically not associated with bilirubin elevations, and cirrhosis was not a risk factor.

MANAGEMENT: Caution is recommended if estrogen-containing products are used in patients receiving ombitasvir/paritaprevir/ritonavir, with or without dasabuvir. Liver function tests should be performed on all patients during the first 4 weeks of treatment and as clinically indicated thereafter. If ALT is elevated above baseline at any time during treatment, the test should be repeated and monitored closely. Therapy should be discontinued if ALT levels remain persistently greater than 10 times the ULN, or if ALT elevations are accompanied by signs or symptoms of liver inflammation or increasing conjugated bilirubin, alkaline phosphatase, or INR. Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice.

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