Cici asked
Prilosec seemed to work after the first dose but 12 hours later the heartburn came back with a vengence. Why?
At a glance
- Prilosec should have beneficial effects after one dose, but it generally takes three to four days of dosing to realize the full effects of the drug.
Answer
While you will likely notice some relief after taking only one dose of Prilosec (omeprazole), it generally takes at least a few days of continuous dosing to experience the full effects of the drug. There are several reasons for this.
Prilosec Only Inhibits Active Acid Pumps
The main reason why it takes a few days of dosing for Prilosec to be most effective is that it only inhibits actively secreting acid pumps.
Prilosec is known as a 'proton pump inhibitor', or PPI for short. These drugs work by inhibiting the 'proton pumps' (i.e. H+/K+ ATPase enzyme system) of parietal cells, which produce stomach acid.
However, PPI drugs only bind to proton pumps that are actively secreting acid, and not all proton pumps are active at once. Therefore, it takes a few days of continuous dosing to bind to, and inhibit, a large number of these pumps.
The prescribing information for Prilosec estimates that it takes around 4 days for maximum acid suppression to occur:
"The inhibitory effect of omeprazole [Prilosec] on acid secretion increases with repeated once-daily dosing, reaching a plateau after four days."
The Use Of Prilosec Increases Gastrin Production
After taking any drug that suppresses acid secretion, including PPIs and H2 blockers (like Zantac), our bodies produce more gastrin to try and compensate for the decrease in acid.
Gastrin is a hormone which stimulates secretion of gastric acid. An increase in gastrin production resulting from the use of antacid drugs can cause what is known as 'acid rebound'.
Studies show that gastrin levels can increases significantly, even after only one dose of an acid-suppressing medication.
Therefore, while you likely get relief from acid symptoms (e.g. heartburn, stomach pain) after taking a single dose of Prilosec, it's not uncommon for it to feel like it is 'wearing off' quickly due to the increase in gastrin production.
So overall, not only is Prilosec not at maximum effectiveness after one dose, there is a subsequent rise in gastrin, so you may be producing more acid than normal.
There is some controversy regarding the long-term effects of taking PPI drugs like Prilosec as it relates to an increase in gastrin production.
Some studies suggest that gastrin increases aren't associated with prolonged negative symptoms after discontinuing therapy while others theorize that PPI drugs should be slowly discontinued after long-term therapy to reduce the likelihood of rebound acid symptoms.
You May Not Be Taking Prilosec Correctly
For maximum effectiveness, it is essential to take PPI drugs like Prilosec correctly.
They should be taken at least 30 to 60 minutes before food.
This allows time for the medication to absorbed and ready to work when you eat food, which will activate the acid pumps in the stomach.
References
- Elsevier ClinicalKey: Omeprazole Monograph
- Serum gastrin levels during long-term omeprazole treatment. PubMed
- Effect of omeprazole on gastric acid secretion and plasma gastrin in man. PubMed
- Rebound acid hypersecretion after long-term inhibition of gastric acid secretion. PubMed
- Withdrawing PPI Therapy After Healing Esophagitis Does Not Worsen Symptoms or Cause Persistent Hypergastrinemia: Analysis of Dexlansoprazole MR Clinical Trial Data. PubMed
- Proton pump inhibitors: how to withdraw treatment. Wiley Online Library
- Prilosec Prescribing Information
