Q: Which of the following requires gastric acidity for absorption? (select one)
A) Dabigatran (Pradaxa)
B) Apixaban (Eliquis)
C) Edoxaban (Savaysa, Lixiana)
D) Rivaroxaban (Xarelto)
Answer: A
Direct oral anticoagulants (DOACs) are now increasingly used instead of Warfarin in most cardiac diseases particularly Atrial Fibrillation (A.fib.). It is imperative to understand the bioavailability, interactions with other drugs, and pharmacokinetics to find a balance between therapeutic dose and risk of bleeding.
Not all DOACs are created equal when it comes to bioavailability. Their response varies depending on the food, kidney function, age, and other variables. Out of all DOACs, Dabigatran and Rivaroxaban need special mention.
Dabigatran is unique out of all DOACs in that though its absorption remains unaffected by food, but capsule needs to be taken intact and requires gastric acidity for absorption. It is mostly cleared by kidney.
Rivaroxaban is interesting in the sense that it behaves differently at lower and higher doses. At 10 mg dose, it has 80-100% bioavailability and stays unaffected by food. But, at 20 mg dose, bioavailability is 66% if taken when fasting, and increased if taken with food!
#pharmacology
#cardiology
References:
1. Gronich N, Stein N, Muszkat M. Association between use of pharmacokinetic-interacting drugs and effectiveness and safety of direct acting oral anticoagulants: Nested case-control study. Clin Pharmacol Ther 2021; 110:1526.
2. Lexicomp Online. Copyright © 1978-2023 Lexicomp, Inc. All Rights Reserved.
3. Drugs@FDA: FDA-Approved Drugs. U.S. Food and Drug Administration. Available https://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm (Accessed on September 9, 2023).
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