Cimetidine is an H2 antagonist used to reduce gastric acid secretion and treat conditions like ulcers and GERD. It undergoes hepatic metabolism and renal excretion. Standard doses are 300-800mg but may be increased to 1600mg for heavy smokers with large duodenal ulcers. Dosing needs to be adjusted for renal impairment and geriatric patients. Cimetidine can cause confusion in the elderly or impaired and B12 deficiency with prolonged use. Patients should be monitored for signs of liver problems, pancreatitis, cardiac issues, or confusion and report them immediately.

1. Protocol of Use for
Cimetidine
DR. AHLAM SUNDUS

2. CIMETIDINE
• H2 Antagonist
• Reduced gastric acid secretion, gastric volume, hydrogen ion
concentration
• Hepatic metabolism
• Urinary excretion
• 80% gastric acid ↓ for 4-5 hrs. after 300mg dose
• Elimination half life ~ 2hrs (adults), 1.4 (children), 3.6hrs (neonates)
• Caution in patient with severe renal failure (drug accumulation)
• Administer with meals

3. Indications
• Short term treatment for active benign gastric and duodenal ulcers
• Gastroesophageal reflux disease
• Hypersecretory conditions (Zollinger-Ellison syndrome, systemic
mastocytosis, multiple endocrine adenomas)
• Heartburn (OTC only)

4. Dosing
• Duodenal ulcer, active: Oral: 300 mg 4 times daily or 800 mg at bedtime or 400
mg twice daily for up to 8 weeks
• Note: Higher doses of 1600 mg at bedtime for 4 weeks may be beneficial for a
subpopulation of patients with larger duodenal ulcers (>1 cm defined
endoscopically) who are also heavy smokers (≥1 pack/day).
• Duodenal ulcer, prophylaxis: Oral: 400 mg at bedtime
• Gastric ulcer, active: Oral: 300 mg 4 times daily or 800 mg at bedtime for up to 8
weeks
• Gastroesophageal reflux disease: Oral: 400 mg 4 times daily or 800 mg twice
daily for 12 weeks
• Pathological hypersecretory conditions: Oral: 300 mg 4 times daily; adjust dose
to patient response; maximum 2.4 g/day
• Heartburn (OTC) 200mg daily 30 min prior to irritating food. Max. 400 dose/day

5. Dose adjustment
• Severe renal impairment: 300 mg every 12 hours; may increase frequency
with caution. When hepatic impairment is also present, further reductions
in dosage may be necessary
• Alternate recommendation
• GFR >50 mL/minute: No dosage adjustment necessary.
• GFR 10 to 50 mL/minute: Administer 50% of normal dose
• GFR <10 mL/minute: 300 mg every 8 to 12 hours
• Hemodialysis: Dose after dialysis
• CCRT: Administer 50% of normal dose
• Peritoneal dialysis: 300 mg every 8 to 12 hours
• Geriatric patients ≥65 years: CrCl <50 mL/minute: Reduce the dose because
of risk of mental status changes

6. Warnings/ Precautions
• Confusion in elderly, severely ill, renal and hepatic impairment
• Vit. B12 deficiency (prolonged treatment > 2years)
• Gastric malignancies
• Hepatic impairment
• Renal impairments require dose adjustment
• Drug-drug interactions (794 drugs)

7. Monitoring parameters
• CBC
• Gastric pH
• Monitor renal function to correct dose
• Occult blood with GI bleeding
• Signs of confusion.

8. Patient education
Educate patient to report immediately to prescriber
• Signs of liver problems (dark urine, fatigue, lack of appetite, nausea, abdominal pain, light-
colored stools, vomiting, or jaundice)
• Signs of Pancreatitis (severe abdominal pain, severe back pain, severe nausea, or vomiting)
• Urinary Retention, Change in Amount of Urine Passed
• Tachycardia, Bradycardia, Abnormal Heartbeat
• Chest pain, Wheezing
• Confusion, Mood Changes, Hallucinations
• Enlarged Breasts (Males), or Sexual Dysfunction

9. THANK YOU