PRILOSEC OTC
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRILOSEC OTC (PRILOSEC OTC).
Proton pump inhibitor that irreversibly inhibits the H+/K+ ATPase enzyme (proton pump) in gastric parietal cells, suppressing gastric acid secretion.
| Metabolism | Primarily metabolized by CYP2C19 and CYP3A4 in the liver; also undergoes non-enzymatic reduction. |
| Excretion | Primarily hepatic metabolism; about 80% of metabolites are excreted in urine, and the remainder in feces via bile. Less than 1% of unchanged drug is excreted in urine. |
| Half-life | Approximately 0.5–1 hour in healthy subjects; longer (up to 3 hours) in slow metabolizers or hepatic impairment. Clinically, the duration of acid suppression exceeds the half-life due to accumulation in parietal cell canaliculi. |
| Protein binding | About 95% bound to albumin and alpha1-acid glycoprotein. |
| Volume of Distribution | Approximately 0.3–0.5 L/kg, indicating distribution primarily into extracellular fluid; higher in gastric mucosa due to active uptake. |
| Bioavailability | Oral: 30–40% after first-pass metabolism; reduced by food (take before meals for optimal effect). |
| Onset of Action | Oral: Peak acid suppression occurs within 2–4 hours after first dose; maximal inhibition after 4 days of once-daily dosing. |
| Duration of Action | Acid suppression persists for 24–72 hours after discontinuation due to irreversible binding to H+/K+ ATPase; clinical effect lasts 24 hours with once-daily dosing. |
| Molecular Weight | 345.42 |
20 mg orally once daily for 14 days for frequent heartburn; may repeat 14-day course every 4 months.
| Dosage form | TABLET, DELAYED RELEASE |
| Renal impairment | No dose adjustment required for renal impairment. (Omeprazole is not significantly renally eliminated.) |
| Liver impairment | In severe hepatic impairment (Child-Pugh C), maximum dose is 20 mg daily. |
| Pediatric use | For gastroesophageal reflux disease (GERD): 1-16 years: weight 5-10 kg: 5 mg once daily; 10-20 kg: 10 mg once daily; ≥20 kg: 20 mg once daily. For erosive esophagitis: weight 5-10 kg: 5 mg once daily; 10-20 kg: 10 mg once daily; ≥20 kg: 20 mg once daily; may increase to 40 mg once daily if inadequate response. |
| Geriatric use | No specific dose adjustment is required, but decreased hepatic clearance may occur; use lowest effective dose and monitor for adverse effects. |
| 1st trimester | Limited human data; animal studies show no evidence of harm. Generally considered safe if clearly needed. |
| 2nd trimester | No known risks; use if clinically indicated. |
| 3rd trimester | No known risks; use if clinically indicated. |
Clinical note
Comprehensive clinical and safety monograph for PRILOSEC OTC (PRILOSEC OTC).
| Placental transfer | Omeprazole crosses the placenta; minimal data in humans but animal studies show low transfer. |
| Breastfeeding | Omeprazole is excreted in breast milk in low concentrations; not expected to cause adverse effects in infants. Considered compatible with breastfeeding. |
| Lactation Rating |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to omeprazole or any component of the formulationUse with rilpivirine-containing products
| Precautions | Long-term use (especially >1 year) increases risk of osteoporosis-related fractures (hip, wrist, spine)., Clostridioides difficile infection risk increased., Hypomagnesemia risk with prolonged use; monitor magnesium levels., Possible vitamin B12 deficiency with long-term use., Acute interstitial nephritis reported., Potential for atrophic gastritis with long-term use., May mask symptoms of gastric malignancy. |
| Food/Dietary | No specific food restrictions; but to reduce heartburn, avoid trigger foods like spicy, acidic, or fatty meals. Take on an empty stomach at least 30 minutes before eating. No significant cytochrome P450-mediated interactions with food. |
Loading safety data…
| L2 (Probably Compatible) |
| Teratogenic Risk | Pregnancy Category C for first trimester (no adequate studies; animal studies show embryocidal effects at high doses). Category B for second and third trimesters (no evidence of teratogenicity in human studies). Avoid unless clearly needed. |
| Fetal Monitoring | Monitor for maternal gastrointestinal symptoms; no specific fetal monitoring required. |
| Fertility Effects | Animal studies show no impairment of fertility at clinically relevant doses. No human data on reproductive effects. |
| Clinical Pearls | PRILOSEC OTC (omeprazole 20 mg) is a proton pump inhibitor (PPI) for frequent heartburn (≥2 days per week). Not for immediate relief; takes 1-4 days for full effect. Max duration 14 days, up to 3 times per year. May increase risk of Clostridioides difficile infection, osteoporosis-related fractures, and hypomagnesemia with prolonged use. Inhibits CYP2C19, potentially altering metabolism of clopidogrel, citalopram, and phenytoin. |
| Patient Advice | Take one capsule daily with a glass of water before first meal of the day. · Do not crush or chew; swallow whole. · Do not take for more than 14 days without consulting a doctor. · Do not take if you have trouble swallowing, or if heartburn persists or worsens. · Avoid alcohol, spicy foods, and fatty foods which may exacerbate symptoms. · Report severe diarrhea, bone pain, or muscle cramps to your healthcare provider. |