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Case 1: Patient P. 56 years old complains about heartburn, more at might and in the morning: burning sensation behind the sternum, appearing immediately after throat hurn with a sour taste. EGDS revealed inflammatory eating; nausea, sore throat, burp wi a sive form of changes in the distal esophagus characteristic of the non-erosive torm l eastroesophageal reflux disease. astroe Station 1 tation 1. Identify the problem (diagnosis): Identity 2. Choose your P-medication for this condition: 3 Dosage form Dosage form Dosage Station 2 5. Pharmacokinetics of the drug 6. Mechanism of action 7. Write a prescription Station 3 8. Duration of treatment 9. Side effects 10. Contraindications

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Case 1 — GERD Clinical Stations

Station 1

1. Diagnosis

Non-erosive Gastroesophageal Reflux Disease (NERD / non-erosive GERD)
GERD is defined as the reflux of stomach contents into the esophagus causing troublesome symptoms or complications. This patient's presentation is classic:
  • Heartburn worse at night and in the morning
  • Burning sensation behind the sternum
  • Sour taste / acid regurgitation
  • Nausea, sore throat, burping
  • EGDS (endoscopy): inflammatory changes in the distal esophagus without erosions → confirming the non-erosive form
— Goldman-Cecil Medicine, p. 3056

2. P-Drug (Personal Drug of Choice)

Omeprazole (a Proton Pump Inhibitor — PPI)
PPIs are the first-line drugs for GERD. Among PPIs, omeprazole 20 mg is the standard choice for non-erosive GERD due to its well-established efficacy, safety profile, and low cost.

3. Dosage Form

Delayed-release capsules (enteric-coated) — oral
PPIs are formulated as acid-resistant enteric-coated capsules/tablets to protect the acid-labile prodrug from gastric destruction.

4. Dose

Omeprazole 20 mg once daily, taken 30–60 minutes before the first meal of the day (to ensure the drug is absorbed and available when proton pumps are actively secreting).
DrugBioavailabilityt½TmaxUsual dose (GERD)
Omeprazole40–65%0.5–1.0 h1–3 h20–40 mg once daily
— Katzung's Basic & Clinical Pharmacology, 16th ed., Table 62-2

Station 2

5. Pharmacokinetics

  • Formulation: Enteric-coated delayed-release capsules (prodrug — inactive until activated)
  • Absorption: After passing through the stomach into the alkaline intestinal lumen, the enteric coating dissolves and the prodrug is absorbed
  • Bioavailability: 40–65% (increases with repeated dosing as gastric acid suppression reduces first-pass degradation)
  • Tmax: 1–3 hours
  • Half-life (t½): 0.5–1.0 hour (plasma)
  • Metabolism: Hepatic — primarily by CYP2C19 (and CYP3A4); subject to genetic polymorphism (poor vs. extensive metabolizers)
  • Distribution: Highly protein-bound (~95%); concentrated in the acidic canalicular space of parietal cells
  • Excretion: Renal (~77% of metabolites) and biliary/fecal
  • Duration of action: Despite short plasma t½, acid suppression lasts >24 hours because the drug covalently binds the proton pump (irreversible)
— Katzung's Basic & Clinical Pharmacology, 16th ed., pp. 1700–1701

6. Mechanism of Action

Omeprazole is a prodrug activated in the acidic environment of the parietal cell secretory canaliculus.
Steps:
  1. The prodrug (weak base) diffuses into the acidic secretory canaliculus of gastric parietal cells
  2. In the acidic environment (pH < 4), it is protonated and converted to its active sulfenamide form
  3. The active form covalently binds (irreversibly) to cysteine residues on the H⁺/K⁺-ATPase (proton pump) — the final enzyme responsible for gastric acid secretion
  4. This irreversibly inhibits the pump, blocking acid secretion regardless of stimulus (histamine, gastrin, acetylcholine)
  5. Acid secretion recovers only after new pump synthesis (18–24 h), explaining prolonged effect despite short plasma half-life
"PPIs are the most effective inhibitors of acid secretion currently available. They suppress acid secretion by >90% with once-daily dosing." — Katzung's Basic & Clinical Pharmacology, 16th ed.

7. Prescription

Rp:
    Omeprazoli 0.02 (20 mg)
    D.t.d. № 14 in caps. enterosolventibus
    S. 1 capsule by mouth once daily, 30–60 minutes before breakfast

    Repeat: ___  Do not repeat: ___

Physician signature: ___________
Date: ___________

Station 3

8. Duration of Treatment

  • Non-erosive GERD (NERD): 4–8 weeks initial course
  • If symptoms resolve → step-down to on-demand therapy or H2-blockers
  • If symptoms recur → long-term/maintenance therapy may be required
  • Reassess at 4 weeks; most patients with NERD achieve symptom control within 4 weeks

9. Side Effects

Common (short-term):
  • Headache, diarrhea, nausea, abdominal pain, flatulence
  • Constipation
Long-term use:
  • Hypomagnesemia (especially >1 year use)
  • Vitamin B12 deficiency (reduced absorption)
  • Iron deficiency (reduced absorption)
  • Increased risk of enteric infections (C. difficile, Salmonella) — due to reduced gastric acid barrier
  • Osteoporosis / fractures (reduced calcium absorption with prolonged use)
  • Community-acquired pneumonia (slight increased risk)
Drug interactions:
  • Inhibits CYP2C19 → raises levels of warfarin, diazepam, phenytoin, clopidogrel (reduced antiplatelet effect)
  • Reduces absorption of drugs requiring acidic environment (ketoconazole, atazanavir, iron)
— Katzung's Basic & Clinical Pharmacology, 16th ed.; Goodman & Gilman's

10. Contraindications

  • Hypersensitivity to omeprazole or any substituted benzimidazole
  • Concurrent use with rilpivirine, atazanavir, or nelfinavir (PPIs reduce their absorption significantly)
  • Caution in severe hepatic impairment (dose reduction may be needed)
  • Caution with clopidogrel (omeprazole inhibits CYP2C19 and may reduce clopidogrel's antiplatelet effect)
  • Pregnancy: Category C — use only if benefits outweigh risks
  • Not recommended as long-term monotherapy without periodic reassessment (risk of masking gastric malignancy)
Summary Table
ItemAnswer
DiagnosisNon-erosive GERD (NERD)
P-DrugOmeprazole
Dosage formDelayed-release enteric-coated capsules
Dose20 mg once daily, 30 min before breakfast
Duration4–8 weeks
MechanismIrreversible inhibition of H⁺/K⁺-ATPase (proton pump) in parietal cells

Short and point

Case 1 — GERD (Non-erosive form)

1. Diagnosis: Non-erosive GERD (NERD)
2. P-Drug: Omeprazole (PPI — first-line)
3. Dosage form: Delayed-release enteric-coated capsules
4. Dose: 20 mg once daily, 30–60 min before breakfast
5. Pharmacokinetics:
  • Bioavailability: 40–65%
  • t½: 0.5–1 h (but effect lasts >24 h)
  • Tmax: 1–3 h
  • Metabolism: hepatic (CYP2C19)
  • Excretion: renal
6. Mechanism of action: Prodrug activated in acidic parietal cell canaliculus → converted to sulfenamide → irreversibly binds H⁺/K⁺-ATPase (proton pump) → blocks acid secretion from all stimuli
7. Prescription:
Rp: Omeprazoli 0.02
D.t.d. № 28 in caps. enterosolventibus
S. 1 cap. orally once daily, 30 min before breakfast
8. Duration: 4–8 weeks
9. Side effects: Headache, diarrhea, nausea; long-term: hypomagnesemia, B12 deficiency, ↑C. difficile risk, osteoporosis
10. Contraindications: Hypersensitivity to benzimidazoles; concurrent atazanavir/rilpivirine; caution with clopidogrel (CYP2C19 interaction)
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