Interactions that have clinical influences
Omeprazole is one of those drugs that is well known in the field of drug-drug interactions. The fact that Omeprazole reduces the activity of liver enzyme CYP 3C19, can modify the transit of several drugs through the liver when taking Omeprazole.
Each drug interaction requires individual considerations. In some cases, you cannot administer the drugs together so you have to choose which one you should substitute. In other situations you need to take them hours apart. Or while taking them together, you need to adjust the dose of one of the medications.
The important message is: whenever you take 2 or more medications, including non-prescriptions, herbals and vitamins, ask a doctor or a pharmacist to check for possible drug-drug interactions.
Omeprazole interactions with Rilpivirine, Indinavir, Atazanavir Saquinavir and Nelfinavir
Some antiretrovirals get reduced their effectiveness when used with Omeprazole. They are rilpivirine, indinavir, atazanavir and nelfinavir. Omeprazole reduces their antiviral effect and increases the chance of the virus to develop drug resistance to these antivirals. For those reasons, it is contraindicated to give Rilpivirine and Omeprazole together. Specialists
recommend to avoid combination of Indinavir, Atazanavir, or Nelfinavir, with Omeprazole.
- Rilpivirine get a significant reduction in absorption when patient is taking Omeprazole.
- Reduction in solubility and absorption of indinavir, is due to Omeprazoleinduced lower acidity in the stomach. It is not advisable to prescribe indinavir
and Omeprazole together, unless patient is taking Ritonavir as well.
- Atazanavir sees effectiveness reduced by 75% with Omeprazole. A combo atazanavir/ritonavir can reduce the effect of Omeprazole.
- Solubility of Nelfinavir is lesser than in patients without reduced acidity in stomach due to Omeprazole. Omeprazole reduces metabolic activation of Nelfinavir by CYP 2C19 enzyme, as well.
Other antivirals, like saquinavir, could reach toxic levels, when patient is taking Omeprazole at the same time. Anyone taking these combination of antiviral and antacid have to be monitored for potential toxicity.
Omeprazole and Tarceva Drug Interactions
Erlotinib and dasatinib have a substantially reduced absorption in patients taking Omeprazole. While on erlotinib or dasatinib do not start taking any antacid including Omeprazole.