Dosing and uses of Prilosec (omeprazole)
Adult dosage forms and strengths
packet
- 2.5mg
- 10mg
suspension
- 2mg/mL
tablet, delayed release
- 20mg
capsule, delayed release
- 10mg
- 20mg
- 40mg
Duodenal Ulcer
20 mg PO qDay for 4-8 weeks
Safety and efficacy of omeprazole for maintenance treatment past 1 year not established
Helicobacter Pylori Infection
Various regimens exist of PPIs combined with antibiotics, 1 example is listed below
20 mg PO q12hr for 10 days, WITH
Amoxicillin 1000 mg PO q12hr, ANd
Clarithromycin 500 mg PO q12hr for 10-14 days
Dosing considerations
- This regimen is available as a prepackaged 10-day supply of omeprazole, amoxicillin, and clarithromycin from Dava Pharms Inc, for eradication of H pylori
Gastric Ulcer
40 mg PO qDay for 4-8 weeks
GERD
20 mg PO qDay for 4 weeks
Erosive Esophagitis
20 mg PO qDay for 4-8 weeks
Maintenance: 20 mg PO qDay for up to 1 year
Hypersecretory Condition (eg, Zollinger-Ellison Syndrome)
60 mg PO qDay (initial) up to 360 mg/day divided q8hr PO
If dose >80 mg, divide it
Dosing Modifications
Hepatic impairment: Not studied; expert analysis recommends a reduction in dose, especially for maintenance of healing of erosive esophagitis
Renal impairment: Dose adjustments not necessary
Pediatric dosage forms and strengths
packet
- 2.5mg
- 10mg
suspension
- 2 mg/mL
tablet/capsule
- 10mg
- 20mg
- 40mg
GERD
Indicated for treatment of GERd
<1 year: Safety and efficacy not established
5-10 kg: 5 mg PO qDay
10-20 kg: 10 mg PO qDay
>20 kg: 20 mg PO qDay
Erosive Esophagitis
Indicated for treatment and to maintain healing of erosive esophagitis caused by acid-mediated GERd
Treatment
- <1 month: Safety and efficacy not established
- Aged 1 month to <1 year
- 3 to <5 kg: 2.5 mg qDay
- 5 to <10 kg: 5 mg qDay
- ≥10 kg: 10 mg qDay
- May treat for up to 6 weeks
- Aged 1-16 years
- 5 to <10 kg: 5 mg PO qDay
- 10 to <20 kg: 10 mg PO qDay
- ≥20 kg: 20 mg PO qDay
- May treat for 4-8 weeks
Maintenance of healing
- <1 year: Safety and efficacy not established
- ≥1 year: Controlled trials for maintenance do not extend beyond 12 months
Neonates (Off-label)
Refractory duodenal ulcer or reflux esophagitis: 0.5-1.5 mg/kg PO qDay for up to 8 weeks
Prilosec (omeprazole) adverse (side) effects
1-10%
Headache (7%)
Abdominal pain (5%)
Diarrhea (4%)
Nausea (4%)
Vomiting (3%)
Flatulence (3%)
Dizziness (2%)
Upper respiratory infection (2%)
Acid regurgitation (2%)
Constipation (2%)
Rash (2%)
Cough (1%)
Frequency not defined
Fracture of bone, osteoporosis-related
Hepatotoxicity (rare)
Agranulocytosis
Anorexia
Gastric polyps
Hip fracture
Alopecia
Atrophic gastritis
Interstitial nephritis (rare)
Pancreatitis (rare)
Rhabdomyolysis
Taste perversion
Abnormal dreams
Toxic epidermal necrolysis (rare)
Postmarketing Reports
Bone fracture
Warnings
Contraindications
Hypersensitivity to omeprazole or other proton pump inhibitors (PPIs)
Cautions
PPIs are possibly associated with increased incidence of Clostridium difficile-associated diarrhea (CDAD); consider diagnosis of CDAD for patients taking PPIs who have diarrhea that does not improve
May require dosage reduction with liver disease
Shown to cause gastric carcinoid tumors in rats with increased doses, but risk in humans unconfirmed
Published observational studies suggest that PPI therapy may be associated with an increased risk for osteoporosis-related fractures of the hip, wrist, or spine, particularly with prolonged (>1 yr), high-dose therapy
Hypomagnesemia may occur with prolonged use (>1 year); adverse effects may result and include tetany, arrhythmias, and seizures; in 25% of cases reviewed, magnesium supplementation alone did not improve low serum magnesium levels and the PPI had to be discontinued
Decreased gastric acidity increases serum chromogranin A (CgA) levels and may cause false-positive diagnostic results for neuroendocrine tumors; temporarily discontinue PPIs before assessing CgA levels
Inhibits hepatic isoenzyme CYP2C19 and may alter metabolism of drugs that are CYP2C19 substrates
PPIs may decrease the efficacy of clopidogrel by reducing the formation of the active metabolite
Daily long-term use (e.g., longer than 3 years) may lead to malabsorption or a deficiency of cyanocobalamin
Gastric atrophy reported with long-term use
Acute interstitial nephritis has been observed in patients taking PPIs
Relief of symptoms does not eliminate the possibility of a gastric malignancy
Therapy increases risk of Salmonella, Campylobacter, and other infections
Pregnancy and lactation
Pregnancy category: C
Lactation: Distributes into human breast milk; use caution
Breast milk peak concentration time ~3 hr following 20 mg dose (peak concentration <7% of peak serum concentrations)
Because of the potential for serious adverse reactions in nursing infants from omeprazole, and the potential for tumorigenicity shown in rat carcinogenicity studies, a decision should be made to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Prilosec (omeprazole)
Mechanism of action
PPI; binds to H+/K+-exchanging ATPase (proton pump) in gastric parietal cells, resulting in suppression of basal and stimulated acid secretion
Absorption
Bioavailability: 30-40%
Onset of action: 1 hr (antisecretory effect)
Duration: 73 hr
Peak plasma time: 0.5-3.5 hr
Peak response (PUD): 2 hr (initial); 5 days (peak)
Distribution
Protein bound: 95-96%
Vd: 0.39 L/kg
Metabolism
Metabolized extensively by hepatic CYP2C19; slow metabolizers are deficient in CYP2C19 enzyme system; plasma concentration can increase by 5-fold or higher in comparison with that found in persons with the enzyme
Metabolites: Hydroxyomeprazole, omeprazole sulfone, omeprazole sulfide (inactive)
Enzymes inhibited: CYP2C19
Elimination
Half-life: 0.5-1 hr; increases to 3 hr with hepatic impairment
Dialyzable: No
Total body clearance: 500-600 mL/min
Excretion: Urine (77%); feces (16-19%; mainly in bile)
Pharmacogenomics
CYP2C19 poor metabolizers
- Asians have ~4-fold higher exposure to omeprazole than whites
- CYP2C19, a polymorphic enzyme, is involved in the metabolism of omeprazole
- ~15-20% of Asians are CYP2C19 poor metabolizers
- Tests are available to identify a patient’s CYP2C19 genotype
- Avoid use in Asian patients with unknown CYP2C19 genotype or those who are known to be poor metabolizers
