Dosing and uses of Tagamet HB (cimetidine)
Adult dosage forms and strengths
injectable solution
- 150mg/mL
oral solution
- 300mg/5mL
tablet
- 200mg
- 300mg
- 400mg (Rx)
- 600mg (Rx)
- 800mg (Rx)
Benign Gastric Ulcer
800 mg PO qHS Or
400 mg PO q12hr Or
300 mg PO q6hr
Duodenal Ulcer
800 mg PO qHS Or
400 mg PO q12hr Or
300 mg PO q6hr
Erosive Gastroesophageal Reflux Disease
800 mg PO q12hr Or
400 mg PO q6hr
Heartburn
Over the counter only
To relieve symptoms: 200 mg PO up to q12hr
To prevent symptoms: 200 mg PO with glass of water right before or any time up to 30 minutes before eating food or drinking beverages that cause heartburn
Pathological Hypersecretory Conditions
300 mg PO q6hr with meals and Hs
Renal Impairment
CrCl<30 mL/min
300 mg IV/IO q12hr
Prevention of upper GI bleeding: 25 mg/hour continuous IV infusion
Other Indications & Uses
PUD (treatment, maintenance), gastric ulcer treatment, GI bleeding prevention in critically ill patients, hypersecretory conditions (e.g., Zollinger-Ellison)
Pediatric dosage forms and strengths
injectable solution
- 150mg/mL
oral solution
- 300mg/5mL
tablet
- 200mg
- 300mg
- 400mg (Rx)
- 600mg (Rx)
- 800mg (Rx)
Duodenal Ulcer (Off-label)
<16 years: Use only if benefit outweighs risks
20-40 mg/kg/day IV/PO divided q6hr
Neonates (<28 days old): 5-20 mg/kg/day IV/PO divided q8-12hr
Infants: 10-20 mg/kg/day IV/PO divided q6-12hr
Geriatric dosage forms and strengths
Not drug of choice in elderly because of increased potential for confusion and drug interactions
Benign Gastric Ulcer
800 mg PO qHS Or
400 mg PO q12hr Or
300 mg PO q6hr
Duodenal Ulcer
800 mg PO qHS Or
400 mg PO q12hr Or
300 mg PO q6hr
Erosive Gastroesophageal Reflux Disease
800 mg PO q12hr Or
400 mg PO q6hr
Tagamet HB (cimetidine) adverse (side) effects
1-10%
Headache (2.1%)
Dizziness (1%)
Somnolence (1%)
Gynecomastia (0.3-4%)
Frequency not defined
Confusion (elderly)
Impotence
Diarrhea
Nausea
Vomiting
Warnings
Contraindications
Hypersensitivity to cimetidine or other H2 receptor antagonists
Cautions
Antiandrogen: may cause feminization & sexual dysfunction in males
Pregnancy and lactation
Pregnancy category: B
Lactation: enters breast milk/not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Tagamet HB (cimetidine)
Mechanism of action
H2-receptor antagonist; blocks H2-receptors of gastric parietal cells, leading to inhibition of gastric secretions
Pharmacokinetics
Bioavailability: PO: 60-70% (undergoes minimal 1st pass metabolism)
Protein Bound: 15-20%
Metabolism: Liver, inhibit microsomal enzymes
Metabolites: Cimetidine sulfoxide, 5-hydroxymethyl derivative (inactive met)
Dialyzable: Yes, removed by HD and Pd
Enzymes inhibited: hepatic CYP1A2, CYP2D6, CYP3A4
Half-Life
- Adults: 2 hr; increases to 4-5 hr with renal impairment
- Infant: 2.1-3.6 hr
Onset
- IV: 30 min
- PO: <1 hr
Duration
- IV/IM: 4-5 hr
- PO: 4-8 hr
Peak Plasma Time
- IM: 15 min
- PO: 45-90 min
Vd
- Adults: 1 L/kg
- Children 1-12 years: 2.13 L/kg
Clearance
- Total Body: 30-48 L/hr
- Renal: 13.8-30 L/hr (removed by HD & PD)
Excretion
- Urine: 48-75%
- Feces: 2-3% (<2% in bile)
Administration
IV/IM Administration
Administered IM with no dilution, Or
Slow direct IV injection over 5 min or more after dilution to a total of 20 mL with compatible diluent (NS), Or
Intermittent IV infusion over 15 to 20 min in at least 50 mL of compatible diluent, Or
Continuous IV infusion in 100 to 1000 mL of compatible diluent over 24 hr
IV Compatibilities
Additive: cefazolin, clindamycin, epinephrine, erythromycin, furosemide, gentamicin, lidocaine, norepinephrine, KCl, vancomycin, verapamil, vit B/C
Syringe: atropine, heparin
Y-site: esmolol, heparin
Not spec: carbenicillin, tetracycline
IV Incompatibilities
Additive: amphotericin B
Syringe: cefazolin, pentobarbital, atropine/pentobarbital, chlorpromazine, heparin (?), secobarbitaL
Y-site: allopurinol, amphotericin B, amsacrine, cefepime, indomethacin, warfarin
IV Preparation
Solution
- Injections: in 5% sodium bicarbonate injection, NS, D5W, D10W or LR to a volume of 20 mL
- Infusions: 300 mg in 100 mL D5W
