Cimetidine pediatric dose calculator
Use this Cimetidine pediatric dose calculator to match the prescribed dose to the exact liquid, tablet, or delayed-release form and the timing instructions that matter for children.
dose calculator basics
Cimetidine pediatric dose calculator details
Use this Cimetidine calculator as the fast parent page for weight-based dose checks, mL conversion, common strengths, and the practical safety steps that generic calculator sites often skip.
Formula
mL per dose = (child weight in kg x prescribed mg/kg/day / doses per day) / medication concentration in mg per mL.
Worked example
For a 20 kg child using 20 mg/kg/day divided 4 times daily with 300 mg/5 mL, calculate the daily mg target, divide by the schedule, then convert that mg amount into mL for the selected product.
Safety checks before using the result
- Use the exact product strength in hand before measuring the dose.
- Confirm maximum dose, age limits, and indication-specific cautions when they apply.
- Escalate urgent symptoms or medication reactions instead of repeating doses from calculator output alone.
Practical dosing guide
Before you measure the dose
Use this page to match the prescribed Cimetidine plan to the form the child can take and the timing instructions that matter most.
- What it helps with
- Cimetidine is an H2 receptor antagonist used in children for reflux symptoms; typically dosed 2–4 times daily.
- Common forms
- Common forms include 300 mg/5 mL oral liquid, 200 mg tablet, and 400 mg tablet.
- How it is usually taken
- Label pediatric experience is very limited: 20–40 mg/kg/day divided 3–4 times a day, not above 1,600 mg/day for reflux.
Cimetidine pediatric medication summary
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.
Cimetidine indications and common pediatric uses
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.
Short-term symptomatic gastroesophageal reflux disease (GERD)
Short-term symptomatic gastroesophageal reflux disease (GERD): Consider only when famotidine is unavailable and PPI therapy is not indicated; reassess within 2-4 weeks.
Nocturnal acid breakthrough in refractory GERD on optimized PPI therapy
Nocturnal acid breakthrough in refractory GERD on optimized PPI therapy: Short-term bedtime adjunct only; avoid in patients on QT-prolonging or narrow-therapeutic-index CYP substrates.
Histamine-mediated flushing in mast cell disorders
Histamine-mediated flushing in mast cell disorders: Occasionally combined with H1 blockade; requires hematology/allergy oversight.
How to give Cimetidine
- Administration and safety guidance for pediatric cimetidine use.
- Shake oral solution well, measure with a calibrated oral syringe, and give according to the prescribed schedule (often before meals and/or at bedtime). If tablets are used, take with water and avoid unsupervised splitting/crushing unless the clinician has provided specific instructions.
- Pair doses with meal alarms (breakfast/lunch/dinner/bedtime) so the q6h cadence sticks. Keep a medication reconciliation sheet in the kitchen and remind caregivers to check with pharmacy before adding OTC products due to interaction risk.
- Do not use sustained-release products without clinician guidance.
Cimetidine side effects, contraindications, and interactions
Short cimetidine courses are often tolerated, but GI upset and headache are common early effects. With higher doses, prolonged use, or renal impairment, neurologic and endocrine adverse effects become more likely and need active monitoring.
Common side effects
- Call promptly for persistent vomiting, confusion, or signs of allergic reaction (hives, swelling, breathing difficulty).
- Report menstrual changes, breast tenderness, or galactorrhea if therapy extends beyond short-term use.
- Review OTC products and supplements before use because cimetidine can alter CYP-mediated drug clearance.
Safety checks
- Renal impairment (eGFR <50 mL/min/1.73 m2): Reduced clearance increases CNS toxicity risk.
- QT prolongation or electrolyte disturbances: Drug interactions and metabolic effects can increase arrhythmia risk.
- Palpitations, syncope, or seizures: Serious arrhythmias or CNS toxicity can occur with interactions.
- Severe confusion or hallucinations: CNS toxicity is more likely with renal impairment.
- Unusual bruising or bleeding: Cimetidine can increase warfarin or phenytoin levels.
Drug interactions
- Review the full medication list with a clinician or pharmacist before combining therapies.
Cimetidine mechanism and clinical pearls
Cimetidine reduces gastric acid secretion by blocking H2 signaling on parietal cells and lowering intracellular cyclic AMP. This improves basal and nocturnal acid control, but cimetidine also inhibits several CYP enzymes, which can raise exposure to interacting medicines. Because interaction burden is often the limiting factor in pediatrics, cimetidine is usually used for targeted short courses with explicit medication-list review.
Review every prescription, OTC, and supplement for CYP1A2, 2C19, 2D6, and 3A4 substrates (theophylline, phenytoin, warfarin, tacrolimus, SSRIs). If polypharmacy exists, switch to famotidine unless absolutely contraindicated.
Use a short planned course (often 1-2 weeks) when bridging therapy or addressing temporary nocturnal symptoms. Document a stop date to avoid automatic long-term refills.
Adjust dose or interval when kidney function is reduced, and use current pediatric weight-based references for age-specific dosing rather than fixed historical defaults.
Counsel families to report agitation, confusion, or seizures, particularly with renal impairment or ICU-level stressors. Stop cimetidine and re-evaluate if symptoms surface.
Frequently asked questions about Cimetidine
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.
It can be taken with or without food, but giving it 30 minutes before meals or at bedtime helps when symptoms are meal-triggered. Consistency in timing keeps acid levels steady.
Give it as soon as remembered unless it is close to the next scheduled dose—then skip and resume the regular schedule. Do not double up. Call if your child misses doses frequently; a once-daily alternative may be easier.
Seek care for persistent vomiting, black or bloody stools, yellowing skin/eyes, confusion, or signs of allergic reaction (rash, swelling, breathing trouble). These symptoms may signal complications or a different diagnosis.
Sources reviewed for Cimetidine
naspghan-gerd-2023
bloodadvances-mast-cell-2022
Cimetidine Hydrochloride Oral Solution prescribing information
DailyMed (NLM)
SourceMast Cell Disorders: Diagnosis and Management
Blood Advances
SourceCimetidine Oral Solution and Tablets – FDA DailyMed
U.S. National Library of Medicine
SourceCimetidine Prescribing Information
DailyMed
Source