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Cimetidine is an H2 receptor antagonist used in children for reflux symptoms; typically dosed 2–4 times daily. It has more drug interaction potential than other H2 blockers.
Cimetidine provides short-term symptom relief for GERD, dyspepsia, and acid hypersecretion when PPIs are not indicated or available.
Multiple daily doses (every 6 hours) are usually required to maintain effect; adherence support is essential.
Strong inhibition of CYP1A2, CYP2D6, and CYP3A4 increases serum levels of many medicines (for example, theophylline, warfarin, phenytoin).
Renal dose adjustments are necessary when creatinine clearance is less than 50 mL/min to avoid accumulation and neurologic adverse effects.
Acid suppression should be reassessed after 4–8 weeks; persistent symptoms warrant evaluation for alternate diagnoses or PPI therapy.
Cimetidine is an older H2 receptor antagonist with significant drug–drug interaction potential; reserve it for short-term acid suppression when safer agents are unavailable or contraindicated.
Use cimetidine sparingly—prefer famotidine or nizatidine for routine pediatric H2 blockade. When cimetidine is employed, keep courses short, reassess frequently, and review the full medication list for CYP-mediated interactions.
| Condition | Age Range | First Line? | Notes |
|---|---|---|---|
| Gastroesophageal reflux symptoms | Infants, children, adolescents | No | Consider when lifestyle measures and antacids fail and before escalating to PPIs; reassess efficacy after 4–8 weeks. |
| Peptic and duodenal ulcer healing | Children and adolescents | No | Use when PPIs are contraindicated or unavailable; combine with H. pylori eradication therapy when indicated. |
| Stress ulcer prophylaxis in hospitalized patients | Critically ill children | No | Alternate option when IV PPIs or famotidine cannot be used; monitor for CNS effects and interactions. |
| Hypersecretory states (e.g., Zollinger–Ellison syndrome) | Children and adolescents | No | Requires high-dose, frequent administration under specialist guidance. |
FDA-approved primary uses with Level A evidence
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Cimetidine is generally well tolerated for short courses, but gastrointestinal upset and headache are common. Longer courses or higher doses can unmask endocrine and neurologic adverse effects, especially when renal function is impaired.
Monitor for GI changes during the first week, review medication lists for CYP interactions, and reassess chronic therapy to avoid endocrine or neuropsychiatric adverse effects.
Diarrhea / loose stools
Common • mild
Nausea or abdominal discomfort
Common • mild
Headache or dizziness
Common • mild
Confusion or agitation (renal impairment or high doses)
Rare • moderate
Gynecomastia or breast tenderness
Uncommon • mild
Vitamin B12 depletion (long-term use)
Rare • moderate
Neutropenia or thrombocytopenia
Very rare • severe
Hypersensitivity reactions (rash, urticaria)
Rare • moderate
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Detailed administration guide for cimetidine in children.
Shake the liquid well and measure each dose with an oral syringe or dosing spoon, not a household spoon. Tablets can be swallowed whole with water. Give doses without regard to meals unless your clinician has a specific plan; bedtime dosing is helpful for nocturnal symptoms.
Set alarms or use a dosing chart because the QID schedule is easy to miss. Avoid aluminum- or magnesium-containing antacids within 1 hour of cimetidine to prevent reduced absorption. Encourage families to limit therapy to the duration recommended by the clinician (often 4–8 weeks) and to schedule reassessment if symptoms persist.
Emergency contact: Seek urgent care for breathing trouble, swelling of the face or throat, severe rash, confusion, or unexplained jaundice.
Consistent timing, accurate measurement, and early reporting of side effects help cimetidine remain a safe bridge therapy for reflux symptoms.
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Cimetidine is a competitive antagonist at histamine H2 receptors on gastric parietal cells and a potent inhibitor of multiple cytochrome P450 isoenzymes.
By blocking H2 receptors, cimetidine suppresses basal and meal-stimulated acid secretion. Its imidazole ring also binds hepatic CYP1A2, 2C9, 2D6, and 3A4, slowing metabolism of co-administered drugs—an important differentiator from other H2 blockers.
Simple explanations and helpful analogies
Receptors, enzymes, and cellular targets
Absorption, metabolism, and elimination
Age-related differences and special populations
Clinical pearls for safer cimetidine use in kids.
Verify interactions, prefer famotidine if polypharmacy, and use shortest effective duration.
Famotidine (Pepcid) has far fewer interactions and is often preferred.
A nighttime dose may better match symptom timing.
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Understanding your child's medication is important. We've created comprehensive guides to help you safely administer Cimetidine and monitor your child's response to treatment.
Many children notice improvement within 1 hour, but consistent relief relies on taking each scheduled dose. If symptoms persist beyond 1–2 weeks, contact your clinician for reassessment.
It interacts with several common drugs (for example, theophylline, phenytoin, warfarin, certain antidepressants). Share a full medication list with your clinician and pharmacist so they can monitor levels or recommend alternatives.
Routine labs are not required for short courses, but clinicians may check kidney or liver function if therapy is prolonged or if the child has underlying conditions.