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Omeprazole

Omeprazole Omeprazole
Omeprazole Omeprazole

Originally approved by the Food and Drug Administration (FDA) in 1989, omeprazole is a proton pump inhibitor that decreases the amount of acid produced in the stomach. It is usually used to treat gastric acid-related disorders.

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Introduction

Originally approved by the Food and Drug Administration (FDA) in 1989, omeprazole is a proton pump inhibitor that decreases the amount of acid produced in the stomach. It is usually used to treat gastric acid-related disorders. [1,2]

Pharmacological Class: Proton pump inhibitor (PPIs)

Indications

  • Helps in the management of gastric and duodenal ulcers
  • Can treat symptoms of gastroesophageal reflux disease (GERD), and other conditions caused by oversecretion of stomach acid
  • Promotes healing of erosive esophagitis (damage to your esophagus caused by stomach acid) 
  • Treat stomach infections by eradicating the bacteria Helicobacter pylori (H. pylori)
  • Conditions prone to hypersecretion such as Zollinger-Ellison syndrome, multiple endocrine adenomas, and systemic mastocytosis  also respond to management with omeprazole
  • Relieves symptoms of heartburn

Pharmachologic action

Omeprazole works by selectively inhibiting the parietal H+/K+ ATPase pump (the final step of acid production). This reduces the secretion of stomach acid. [3] Omeprazole binds covalently to cysteine residues via disulfide bridges on the alpha subunit of the H+/K+ ATPase pump, suppressing the acid secretion. This anti-secretory effect is dose-related and leads to the suppression of both basal and stimulated acid secretion. [2]

Dosage

(a) Active duodenal ulcer

Adults: 20 mg P.O. (medication is taken by mouth twice a day) daily for 4 to 8 weeks.


(b) Gastric ulcer

Adults: 40 mg P.O. daily for 4 to 8 weeks.


(c) Severe erosive esophagitis; symptomatic, poorly responsive GERD

Adults: 20 mg P.O. daily for 4 to 12 weeks. Patients with GERD should have failed initial therapy with an H2 antagonist. May continue with a maintenance dosage of 20 mg daily for up to 1 year.


(d) Pathologic hypersecretory conditions (such as Zollinger-Ellison syndrome)

Adults: Initial dosage is 60 mg P.O. daily; adjust dosage based on patient response. Administer daily doses exceeding 80 mg in divided doses. Doses up to 120 mg t.i.d. (three times daily) have been administered. Continue therapy as long as clinically indicated.


(e) H.pylori eradication to lower duodenal ulcer recurrence risk

Dual therapy: Adults: 40 mg P.O. q morning plus 500 mg clarithromycin P.O. t.i.d. for 14 days followed by 14 days of omeprazole 20 mg daily.

Triple therapy: Adults: 20 mg P.O. b.i.d. (twice daily) plus 500 mg clarithromycin P.O. b.i.d. plus 1,000 mg amoxicillin P.O. b.i.d. for 10 days. For patients with an ulcer present at the time that therapy starts, an additional 18 days of omeprazole 20 mg once daily is suggested alone for symptom relief and ulcer healing.


(f) Dosage adjustment: Patients with liver disease may require dosage adjustments. Due to the increased bioavailability of omeprazole in Asian patients, they may need dosage adjustments.

Pharmacokinetics

Absorption:

Absorption of omeprazole occurs rapidly, with peak plasma concentrations of omeprazole achieved within 0.5-3.5 hours. [2] Bioavailability is about 40% because of instability in gastric acid as well as a significant first-pass effect. Bioavailability increases slightly with repeated dosing, possibly due to the drug’s effect on gastric acidity. [4]

Volume of distribution

Approximately 0.3 L/kg, corresponding to the volume of extracellular water

Protein binding

About 95% of omeprazole is bound to human plasma proteins


Metabolism:

Omeprazole is primarily metabolized in the liver by the cytochrome P450 (CYP) enzyme. CYP2C19 is responsible for the formation of hydroxyomeprazole (the major metabolite found in plasma). The remaining metabolism depends on CYP3A4 that is responsible for the formation of omeprazole sulphone.  


Excretion:

Omeprazole is majorly excreted via the kidneys. The plasma half-life is 1/2 to 1 hour in healthy subjects and approximately 3 hours in patients with liver impairment. The clearance of omeprazole is as follows:

(a) Healthy subject (delayed-release capsule), total body clearance 500 - 600 mL/min

(b) Hepatic impairment plasma clearance: 70 mL/min

(c) Geriatric plasma clearance: 250 mL/min [2]

Contraindications

Contraindicated in patients having following the following conditions:

  • an autoimmune disease
  • CYP2C19 poor metabolizer
  • inadequate vitamin B12
  • Hepatic impairment
  • Hypersensitivity reactions
  • diarrhea from infection with Clostridium difficile bacteria
  • osteoporosis
  • low amount of magnesium in the blood
  • subacute cutaneous lupus erythematosus
  • interstitial nephritis (a type of kidney inflammation)
  • systemic lupus erythematosus
  • weak or broken bones

Drug interaction

Tacrolimus, Digoxin, Phenytoin, Warfarin, Diazepam, Citalopram, Methotrexate, Cilostazol, Saquinavir: Concomitant administration of omeprazole may increase the serum levels of these drugs in your body.

Ampicillin esters, Ketoconazole, Mycophenolate mofetil (MMF), Iron salts, Erlotinib: Concomitant administration of omeprazole may interfere with the absorption of these drugs and decrease their serum levels in your body.

Voriconazole: This drug may increase the levels of omeprazole in your body. This, in turn, raises the risk of side effects from omeprazole.

Rifampin: This drug may decrease the levels of omeprazole in your body and makes the drug less effective.

Clopidogrel: Omeprazole may reduce the effects of clopidogrel, causing your blood to clot.

Atazanavir, rilpivirine, and nelfinavir: Concomitant administration of omeprazole may reduce plasma levels and effects of these drugs, and could make them less effective over time.

Side effects

More common side effects

  • Side effects in adults can include: Stomach pain, Headache, Diarrhea, Nausea, Vomiting, Gas
  • Side effects in adults can include: Fever plus the side effects witnessed in adults

Serious side effects

  • Low magnesium levels:  Using omeprazole for 3 months or longer can cause low magnesium levels. Symptoms can include: Abnormal or fast heart rate, muscle aches, Seizures, tremors, muscle weakness, spasms of your hands and feet, spasm of your voice box, dizziness, cramps
  • Severe diarrhea: This may be caused by a Clostridium difficile infection in your intestines. Symptoms can include: Stomach pain, watery stool, fever
  • Vitamin B-12 deficiency. Using omeprazole for longer than 3 years can make it harder for your body to absorb vitamin B-12. Symptoms can include: Neuritis, poor muscular coordination, nervousness, numbness or tingling in your hands and feet, changes in menstruation
  • Inflammation of your stomach lining: Symptoms can include: Nausea, stomach pain, vomiting, weight loss
  • Systemic lupus erythematosus (SLE): Symptoms can include: Heartburn, fever, weight loss,  tiredness, blood clots
  • Fundic gland polyps (abnormal tissue growth in the upper part of your stomach that doesn’t usually cause symptoms)
  • Cutaneous lupus erythematosus (CLE). Symptoms can include: Raised, scaly, red or purple rash on the body,  Rash on the skin and nose
  • Kidney damage: Symptoms can include: Changes in urination, flank pain (pain in your side and back),
  • Bone fractures

Precautions

  • Should be used with caution in children since this drug has not been studied in children with gastric ulcers, duodenal ulcers, or hypersecretory conditions. This drug has not been shown to be safe or effective in children younger than 1 year of age with GERD
  • Should be used with caution in older patients since they have diminished kidney function. This may result in slow processing of drug and raises the risk of side effects.
  • In women who are breastfeeding, omeprazole can pass into breast milk and may produce side effects in the child
  • Should be avoided in pregnant women
  • Should not be used in patients with liver problems
  • Should not be used in patients with  vitamin B-12 deficiency
  • Should be avoided in osteoporosis patients as it increases the risk of hip, wrist, and spine fractures
  • Should be used with caution in patients having low magnesium levels in the blood
  • Should not be used in patients allergic to other PPIs as it may cause death

Clinical evidence

Aprotinin or remdesivir with omeprazole may help to treat COVID-19

In Germany, recent drug research demonstrated that omeprazole hampered the viral formation of SARS-CoV-2 beyond therapeutic plasma concentrations at 8 µM. However, at therapeutic concentrations, it elevated the anti-SARS-CoV-2 effects of aprotinin (an approved protease inhibitor) and remdesivir by 2.7-fold and tenfold, respectively. Therefore, aprotinin or remdesivir with omeprazole may represent as potent candidates for management of COVID-19 [9]

References

    1. https://www.medicines.org.uk/emc/product/10340/smpc [Last accessed on: 29 August, 2020]
    2. https://www.drugbank.ca/drugs/DB00338 [Last accessed on: 27 July, 2020]
    3. https://www.ncbi.nlm.nih.gov/books/NBK539786/ [Last accessed on: 27 July, 2020]
    4. https://www.glowm.com/resources/glowm/cd/pages/drugs/o004.html  [Last accessed on: 27 July, 2020]
    5. https://www.webmd.com/drugs/2/drug-3766-2250/omeprazole-oral/omeprazole-delayed-release-tablet-oral/details/list-contraindications [Last accessed on: 27 July, 2020]
    6. https://www.healthline.com/health/omeprazole-oral-capsule-sprinkles#interactions [Last accessed on: 27 July, 2020]
    7. https://www.healthline.com/health/omeprazole-oral-capsule-sprinkles#side-effects [Last accessed on: 27 July, 2020]
    8. https://www.healthline.com/health/omeprazole-oral-capsule-sprinkles#other-warnings [Last accessed on: 27 July, 2020]
    9. Aguila EJ, Cua IH. Repurposed GI Drugs in the Treatment of COVID-19. Digestive Diseases and Sciences. 2020 Jun 29:1-2.

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