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Cimetidine


Pronunciation

 (sye MET i deen)


U.S. Brand Names

 Tagamet®; Tagamet® HB 200 [OTC]


Generic Available

 Yes


Canadian Brand Names

 Apo-Cimetidine®; Gen-Cimetidine; Novo-Cimetidine; Nu-Cimet; PMS-Cimetidine; Tagamet® HB


Use

 Short-term treatment of active duodenal ulcers and benign gastric ulcers; long-term prophylaxis of duodenal ulcer; gastric hypersecretory states; gastroesophageal reflux; prevention of upper GI bleeding in critically-ill patients; labeled for OTC use for prevention or relief of heartburn, acid indigestion, or sour stomach


Use - Unlabeled/Investigational

 Part of a multidrug regimen for H. pylori eradication to reduce the risk of duodenal ulcer recurrence


Pregnancy Risk Factor

 B


Lactation

 Enters breast milk/compatible


Contraindications

 Hypersensitivity to cimetidine, any component of the formulation, or other H2 antagonists


Warnings/Precautions

 Adjust dosages in renal/hepatic impairment or patients receiving drugs metabolized through the P450 system


Adverse Reactions

1% to 10%:

Central nervous system: Dizziness, agitation, headache, drowsiness

Gastrointestinal: Diarrhea, nausea, vomiting

<1%: Bradycardia, hypotension, tachycardia, confusion, fever, rash, gynecomastia, edema of the breasts, decreased sexual ability, neutropenia, agranulocytosis, thrombocytopenia, increased AST/ALT, myalgia, elevated creatinine


Overdosage/Toxicology

 Treatment is symptomatic and supportive. There is no reported experience with intentional overdose. Reported ingestion of 20 g have had transient side effects seen with recommended doses. Animal data has shown respiratory failure, tachycardia, muscle tremor, vomiting, restlessness, hypotension, salivation, emesis, and diarrhea.


Drug Interactions

 Inhibits CYP1A2 (moderate), 2C8/9 (weak), 2C19 (moderate), 2D6 (moderate), 2E1 (weak), 3A4 (moderate)

Note: There are many potential interactions. Listed are the most significant ones.

Alfentanil; Increased serum concentration; monitor for toxicity.

Amiodarone's serum concentration is increased; avoid concurrent use.

Benzodiazepine's (except lorazepam, oxazepam, temazepam) serum concentration is increased; consider alternative H2 antagonist or monitor for benzodiazepine toxicity.

Beta-blockers (except atenolol, betaxolol, bisoprolol, nadolol, penbutolol) effects may be increased; use a renally-eliminated beta-blocker or alternative H2 antagonist.

Calcium channel blockers serum concentration is increased; monitor for toxicity.

Carbamazepine's plasma concentrations may increase transiently (1 week). Monitor for carbamazepine toxicity or use an alternative H2 antagonist.

Carmustine's myelotoxicity is increased; avoid concurrent use.

Cefpodoxime's and cefuroxime's oral absorption may be reduced by increased pH; consider alternative antibiotic.

Cisapride's bioavailability is increased; avoid concurrent use.

Citalopram's serum concentration is increased; use an alternative H2 antagonist or adjust citalopram's dose.

Cyclosporine's serum concentration may increase; monitor cyclosporine levels.

CYP1A2 substrates: Cimetidine may increase the levels/effects of CYP1A2 substrates. Example substrates include aminophylline, fluvoxamine, mexiletine, mirtazapine, ropinirole, theophylline, and trifluoperazine.

CYP2C19 substrates: Cimetidine may increase the levels/effects of CYP2C19 substrates. Example substrates include citalopram, diazepam, methsuximide, phenytoin, propranolol, and sertraline.

CYP2D6 substrates: Cimetidine may increase the levels/effects of CYP2D6 substrates. Example substrates include amphetamines, selected beta-blockers, dextromethorphan, fluoxetine, lidocaine, mirtazapine, nefazodone, paroxetine, risperidone, ritonavir, thioridazine, tricyclic antidepressants, and venlafaxine.

CYP2D6 prodrug substrates: Cimetidine may decrease the levels/effects of CYP2D6 prodrug substrates. Example prodrug substrates include codeine, hydrocodone, oxycodone, and tramadol.

CYP3A4 substrates: Cimetidine may increase the levels/effects of CYP3A4 substrates. Example substrates include benzodiazepines, calcium channel blockers, cyclosporine, mirtazapine, nateglinide, nefazodone, sildenafil (and other PDE-5 inhibitors), tacrolimus, and venlafaxine. Selected benzodiazepines (midazolam and triazolam), cisapride, ergot alkaloids, selected HMG-CoA reductase inhibitors (lovastatin and simvastatin), and pimozide are generally contraindicated with strong CYP3A4 inhibitors.

Delavirdine's absorption is decreased; avoid concurrent use with H2 antagonists.

Flecainide's serum concentration is increased, especially in patients with renal failure.

Ketoconazole, fluconazole, itraconazole (especially capsule): Decreased serum concentration; avoid concurrent use with H2 antagonists.

Lidocaine's serum concentration is increased; use alternative H2 antagonist.

Melphalan's serum concentration may be decreased; monitor for reduced efficacy.

Meperidine: Increased serum concentration; monitor for toxicity.

Moricizine's serum concentration is increased; monitor for toxicity.

Paroxetine's serum concentration is increased.

Phenytoin toxicity; avoid concurrent use.

Propafenone's serum concentration is increased; monitor for toxicity.

Quinolones: Renal elimination of quinolone antibiotics may be decreased.

Tacrine's plasma concentration is increased; consider alternative H2 antagonist.

TCAs serum concentration is increased; consider alternative H2 antagonist or monitor for TCAs toxicity.

Theophylline's serum concentration is increased; consider alternative H2 antagonist.

Warfarin's INR is increased; cimetidine's effect is dose-related. Use an alternative H2 antagonist if possible or monitor INR closely and adjust warfarin dose as needed.


Ethanol/Nutrition/Herb Interactions

Ethanol: Avoid ethanol (may enhance gastric mucosal irritation).

Food: Cimetidine may increase serum caffeine levels if taken with caffeine. Cimetidine peak serum levels may be decreased if taken with food.

Herb/Nutraceutical: St John's wort may decrease cimetidine levels.


Stability

Intact vials of cimetidine should be stored at room temperature and protected from light; cimetidine may precipitate from solution upon exposure to cold but can be redissolved by warming without degradation

Stability at room temperature:

Prepared bags: 7 days

Premixed bags: Manufacturer expiration dating and out of overwrap stability: 15 days

Stable in parenteral nutrition solutions for up to 7 days when protected from light

Physically incompatible with barbiturates, amphotericin B, and cephalosporins


Compatibility

 Stable in D5LR, D5 1 /4NS, D5 1 /2NS, D5NS, D5W, D10W, D10NS, LR, sodium bicarbonate 5%, NS; variable stability (consult detailed reference) in TPN

Y-site administration: Compatible: Acyclovir, amifostine, aminophylline, atracurium, aztreonam, cisatracurium, cisplatin, cladribine, clarithromycin, cyclophosphamide, cytarabine, diltiazem, docetaxel, doxorubicin, doxorubicin liposome, enalaprilat, esmolol, etoposide, filgrastim, fluconazole, fludarabine, foscarnet, gatifloxacin, gemcitabine, granisetron, haloperidol, heparin, hetastarch, idarubicin, inamrinone, labetalol, levofloxacin, linezolid, melphalan, meropenem, methotrexate, midazolam, milrinone, ondansetron, paclitaxel, pancuronium, piperacillin/tazobactam, propofol, remifentanil, sargramostim, tacrolimus, teniposide, theophylline, thiotepa, tolazoline, topotecan, vecuronium, vinorelbine, zidovudine. Incompatible: Allopurinol, amphotericin B cholesteryl sulfate complex, amsacrine, cefepime, indomethacin, warfarin. Variable (consult detailed reference): TPN

Compatibility in syringe: Compatible: Atropine, butorphanol, diatrizoate meglumine and diatrizoate sodium, diatrizoate sodium, diazepam, diphenhydramine, doxapram, droperidol, fentanyl, glycopyrrolate, heparin, hydromorphone, hydroxyzine, iohexol, iopamidol, iothalamate meglumine, lorazepam, meperidine, midazolam, morphine, nafcillin, nalbuphine, penicillin G sodium, pentazocine, perphenazine, prochlorperazine edisylate, promazine, promethazine, scopolamine, sodium acetate, sodium chloride, sodium lactate. Incompatible: Atropine with pentobarbital, cefamandole, cefazolin, chlorpromazine, ioxaglate meglumine and ioxaglate sodium, pentobarbital, secobarbital

Compatibility when admixed: Compatible: Acetazolamide, amikacin, aminophylline, ampicillin, atracurium, cefoperazone, cefoxitin, ceftazidime, chlorothiazide, clindamycin, colistimethate, cryptenamine, dexamethasone sodium phosphate, digoxin, epinephrine, erythromycin lactobionate, ethacrynate sodium, floxacillin, flumazenil, furosemide, gentamicin, insulin (regular), isoproterenol, lidocaine, lincomycin, meropenem, metaraminol, methylprednisolone sodium succinate, metoclopramide, norepinephrine, penicillin G potassium, phytonadione, polymyxin B sulfate, potassium chloride, protamine, quinidine gluconate, sodium nitroprusside, tacrolimus, vancomycin, verapamil, vitamin B complex, vitamin B complex with C. Incompatible: Amphotericin B, barbiturates. Variable (consult detailed reference): Cefamandole, cefazolin


Mechanism of Action

 Competitive inhibition of histamine at H2-receptors of the gastric parietal cells resulting in reduced gastric acid secretion, gastric volume and hydrogen ion concentration reduced


Pharmacodynamics/Kinetics

Onset of action: 1 hour

Duration: 6 hours

Distribution: Crosses placenta; enters breast milk

Protein binding: 20%

Metabolism: Partially hepatic

Bioavailability: 60% to 70%

Half-life elimination: Neonates: 3.6 hours; Children: 1.4 hours; Adults: Normal renal function: 2 hours

Time to peak, serum: Oral: 1-2 hours

Excretion: Primarily urine (as unchanged drug); feces (some)


Dosage

Children: Oral, I.M., I.V.: 20-40 mg/kg/day in divided doses every 6 hours

Children 12 years and Adults: Oral: Heartburn, acid indigestion, sour stomach (OTC labeling): 200 mg up to twice daily; may take 30 minutes prior to eating foods or beverages expected to cause heartburn or indigestion

Adults:

Short-term treatment of active ulcers:

Oral: 300 mg 4 times/day or 800 mg at bedtime or 400 mg twice daily for up to 8 weeks

I.M., I.V.: 300 mg every 6 hours or 37.5 mg/hour by continuous infusion; I.V. dosage should be adjusted to maintain an intragastric pH 5

Patients with an active bleed: Administer cimetidine as a continuous infusion (see above)

Duodenal ulcer prophylaxis: Oral: 400-800 mg at bedtime

Gastric hypersecretory conditions: Oral, I.M., I.V.: 300-600 mg every 6 hours; dosage not to exceed 2.4 g/day

Helicobacter pylori eradication (unlabeled use): 400 mg twice daily; requires combination therapy with antibiotics

Dosing adjustment/interval in renal impairment: Children and Adults:

Clcr 20-40 mL/minute: Administer every 8 hours or 75% of normal dose

Clcr 0-20 mL/minute: Administer every 12 hours or 50% of normal dose

Hemodialysis: Slightly dialyzable (5% to 20%)

Dosing adjustment/comments in hepatic impairment: Usual dose is safe in mild liver disease but use with caution and in reduced dosage in severe liver disease; increased risk of CNS toxicity in cirrhosis suggested by enhanced penetration of CNS


Administration

Oral: Administer with meals so that the drug's peak effect occurs at the proper time (peak inhibition of gastric acid secretion occurs at 1 and 3 hours after dosing in fasting subjects and approximately 2 hours in nonfasting subjects; this correlates well with the time food is no longer in the stomach offering a buffering effect)

Injection: May be administered as a slow I.V. push or preferably as an I.V. intermittent or I.V. continuous infusion. Administer each 300 mg (or fraction thereof) over a minimum of 5 minutes when giving I.V. push. Give intermittent infusion over 15-30 minutes for each 300 mg dose. Intermittent infusions are administered over 15-30 minutes at a final concentration not to exceed 6 mg/mL; for patients with an active bleed, preferred method of administration is continuous infusion.


Monitoring Parameters

 CBC, gastric pH, occult blood with GI bleeding; monitor renal function to correct dose.


Test Interactions

 Increased creatinine, AST, ALT


Patient Education

 Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy unless approved by prescriber. Take with meals. Do not increase dose or frequency without consulting prescriber. Limit xanthine-containing foods and beverages which may decrease iron absorption. To be effective, continue to take for the prescribed time (possibly 4-8 weeks) even though symptoms may have improved. Smoking decreases the effectiveness of cimetidine (stop smoking if possible). Avoid alcohol and caffeine. May cause headache, dizziness, agitation (use caution when driving or engaging in any potentially hazardous tasks until response to drug is known); nausea or vomiting (small, frequent meals, frequent mouth care, chewing gum, or sucking lozenges may help); or diarrhea (buttermilk, boiled milk, or yogurt may help). Report persistent diarrhea; black tarry stools or coffee ground-like emesis; dizziness, confusion, or agitation; rash; unusual bleeding or bruising; sore throat; or fever.


Anesthesia and Critical Care Concerns/Other Considerations

 Cimetidine has extensive drug interactions, particularly with antiarrhythmics (lidocaine, phenytoin, procainamide, quinidine) and may also increase the likelihood of theophylline and cyclosporine toxicity. Because of inhibition of warfarin metabolism, cimetidine may increase INR in patients on anticoagulation therapy.


Cardiovascular Considerations

 Cimetidine has extensive drug interactions, particularly with antiarrhythmics (lidocaine, phenytoin, procainamide, quinidine) and may also increase the likelihood of theophylline and cyclosporine toxicity. Because of inhibition of warfarin metabolism, cimetidine may increase INR in patients on anticoagulation therapy.


Dental Health: Effects on Dental Treatment

 No significant effects or complications reported


Dental Health: Vasoconstrictor/Local Anesthetic Precautions

 No information available to require special precautions


Mental Health: Effects on Mental Status

 May cause agitation or drowsiness; rare reports of confusion


Mental Health: Effects on Psychiatric Treatment

 Rare reports of agranulocytosis; use caution with clozapine and carbamazepine; may inhibit the metabolism of TCAs and benzodiazepines; monitor for adverse effects


Dosage Forms

Infusion, as hydrochloride [premixed in NS]: 300 mg (50 mL)

Injection, solution, as hydrochloride: 150 mg/mL (2 mL, 8 mL) [8 mL size contains benzyl alcohol]

Liquid, oral, as hydrochloride: 300 mg/5 mL (240 mL, 480 mL) [contains alcohol 2.8%; mint-peach flavor]

Tablet: 200 mg [OTC], 300 mg, 400 mg, 800 mg

Tagamet: 300 mg, 400 mg

Tagamet® HB 200: 200 mg


References

Burkhart KK, Janco N, Kulig KW, et al, "Cimetidine as Adjunctive Treatment for Acetaminophen Overdose," Hum Exp Toxicol , 1995, 14(3):299-304.

Fennerty MD and Higbee M, "Drug Therapy of Gastrointestinal Disease," Geriatric Pharmacology , Bressler R and Katz MD, eds, New York, NY: McGraw-Hill, 1993, 585-608.

Garcia Rodriguez LA and Jick H, "Risk of Gynaecomastia Associated With Cimetidine, Omeprazole, and Other Antiulcer Drugs," BMJ , 1994, 308(6927):503-6.

Inoue A, Teramae H, Hisa T, et al, "Fixed Drug Eruption Due to Cimetidine," Acta Derm Venereol , 1995, 75(3):250.

Koren G and Zemlickis DM, "Outcome of Pregnancy After First Trimester Exposure to H2-Receptor Antagonists," Am J Perinatol , 1991, 8(1):37-8.

Krenzelok EP, Litovitz T, Lippold KP, et al, "Cimetidine Toxicity: An Assessment of 881 Cases," Ann Emerg Med , 1987, 16(11):1217-21.

Lambert J, Mobassaleh M, and Grand RJ, "Efficacy of Cimetidine for Gastric Acid Suppression in Pediatric Patients," J Pediatr , 1992, 120(3):474-8.

Lloyd CW, Martin WJ, and Taylor BD, "The Pharmacokinetics of Cimetidine and Metabolites in a Neonate," Drug Intell Clin Pharm , 1985, 19(3):203-5.

Lloyd CW, Martin WJ, Taylor BD, et al, "Pharmacokinetics and Pharmacodynamics of Cimetidine and Metabolites in Critically Ill Children," J Pediatr , 1985, 107(2):295-300.

Mogelnicki SR, Waller JL, and Finlayson DC, "Physostigmine Reversal of Cimetidine-Induced Mental Confusion," JAMA , 1979, 241(8):826-7.

Penston J and Wormsley G, "Adverse Reactions and Interactions With H2-Receptor Antagonists," Med Toxicol Adverse Drug Exp , 1986, 1(3):192-216.

Sawyer D, Conner CS, and Scalley, "Cimetidine: Adverse Reactions and Acute Toxicity," Am J Hosp Pharm , 1981, 38(2):188-97.

Somogyi A and Gugler R, "Clinical Pharmacokinetics of Cimetidine," Clin Pharmacokinet , 1983, 8(6):463-95.

Somogyi A and Muirhead M, "Pharmacokinetic Interactions of Cimetidine 1987," Clin Pharmacokinet , 1987, 12(5):321-66.


International Brand Names

 Aciloc® (DK); Aci-med® (ZA); Acinil® (DK, SE); Acitak® (GB); Adco-Cimetidine® (ZA); Aidar® (TH); Algitec® (IE); Ali Veg® (ES); Alserine® (TH); Altramet® (DE, PL, RO, SI); Altramet® [inj.] (RO); Apo-Cimetidine® (CA, NZ, ZA); Asiloc® (RO); Azucimet® (DE); Belomet® (HR, RO); Benomet® (ID); Bio-Cimetidine® (ZA); Biomag® (IT); Brumetidina® (IT); Cedine® (IE); Cementin® (SG); Cemidin® (IL, RO); Cencamet® (TH); Cidine® (TH); Cigamet® (TH); Cimagen® (IE); Cimal® (NO); Cime AbZ® (DE); Cimebeta® (DE); Cimecodan® (DK); Cimedine® (LB, RO); Cime Eu Rho® (DE); Cimehexal® (AU, DE, LU, RO); Cimeldine® (HU, IE); Cimephar® (BE); Cime-Puren® (DE); Cimesan® (RO); Cimetag® [compr.] (AT, IL); Cimetag® [inj.] (IL); Cimetase® (MX); Cimet® (ID); Cimetid® (BD, NO); Cimetidin 1A Farma® (DK); Cimetidina® (BR, CL, RO); Cimetidin acis® (DE); Cimetidina EG® (IT); Cimetidin AL® (DE, HU); Cimetidin Atid® (DE); Cimetidin® (BG); CIMetidin® (CZ); Cimetidine Alpharma® (SG); Cimetidine-BC® (AU, BE); Cimetidine Beacons® (SG); Cimetidine® (GB, NZ, PL, RO); Cimetidine Hovid® (SG); Cimetidine Lannacher® (RU); Cimetidine PRAFA® (ID); Cimetidine-ratiopharm® (BE); Cimetidin Genericon® (AT); Cimetidin Heumann® (DE); Cimetidin® (HU, NO, RO); Cimetidin Interpharm® (AT); Cimetidin-Mepha® (CH); Cimetidin NM® (DK); Cimetidin Pharmagen® (RO); Cimetidin Stada® (DE); Cimetidin Stada® [inj.] (DE); Cimetidinum® (PL); cimetidin von ct® (DE); cimetidin von ct® [inj.] (DE); Cimetil® (BR); Cimetimed® (BE); Cimetin® (BR, CZ, EC); Cimetine® (TH); Cimet-P® (TH); Cimetum® (AR); Cimex-Retard® (BR); Cimidine® (TH); Cimi® (IL); CimLich® (DE, LU); Cimlok® (ZA); Cim® (PT); Cimulcer® (SG, TH); Cinadine® (ZA); Citidine® (HK, SG, TH); Climatidine® (BR); Climetidina Teva® (IT); Clinimet® (TH); Cloridrato de Cimetidina® (BR); C.M.D.® (TH); Corsamet® (ID); Cymi® (ZA); Cytine® (NZ); Dina® (IT); Doccimeti® (BE); Duomet® (BR, NZ); Duotric® (TH); Duractin® (AU); duraH2® (DE); Dyspamet® (CY, GB, IE, JO, KW, LB, SY); Erlmetin® (SG); Fremet® (ES); Galenamet® (GB, IE); Gastrodine® (BR); Gastrodin® (TH); Gastroprotect® (DE); Gen-Cimetidine (CA); Geramet® (IE); H2 Blocker-ratiopharm® (DE, LU); H2 Blocker-ratiopharm® [inj.] (DE); Hexamet® (ZA); Histodil® (HU, PL, RO, RU); Histodil® [inj.] (HU, PL, RO); Hocimin® (DK); Ipirovet® (RO); Iwamet® (TH); Lenamet® (ZA); Lock-2E® (CZ); Magicul® (AU); Malimed® (CH); Manomet® (TH); Mansal® (ES); Med-Gastramet® (TH); Milamet® (TH); Neutromed® [compr.] (AT); Neutronorm® (AT, RU); Notul® (IT); Novamet® (DK); Novo-Cimetidine (CA); Nuardin® (BE, LU); Nu-Cimet (CA); Nulcer® (ID); Nuradin® (BE); Pallia® (HK); Peptica® (TH); Peptimax® (GB); Phimetin® (GB); Pinamet® (IE); PMS-Cimetidine (CA); Pondarmett® (TH); Primamet® (CZ, RU); Rinadine® (TH); Rolab-Cimetidine® (ZA); Sabax Cimetidine® (ZA); Sanmetidin® (ID); Secadine Syrup® (ZA); Secadine Tablets® (ZA); Shintamet YSP® (SG); Siamidine® (TH); Sigacimet® (DE); Sigmetadine® (AU); Simaglen® (TH); Simex® (TH); Sodexx® (AT); Stomakon® (BR); Stomédine® (FR); Stomet® (BR, IT); Tagamet® (AR, AU, BE, BR, CR, CY, DE, DO, ES, FR, GB, GT, HK, HN, ID, IE, IL, IT, JO, KW, LB, LU, MX, NL, NO, PA, PL, PT, RO, SE, SG, SV, SY, TH, ZA); Tagamet® HB (CA); Temic® (IT); Tenomet® (CY); Timet® (BG, KW, LB, MA, MY, SY); Topcimet® (BE); Ulcedin® (BR, IT); Ulcedine® (BR, ID, TH); Ulcemet® (TH); Ulceracid® (BR); Ulcerfen® (AR); Ulcimet® (AR, BR, TH); Ulcim Injection® (ZA); Ulcomedina® (IT); Ulcometin® (AT); Ulcostad® (AT); Ulcostad® [inj.] (AT); Ulcumet® (ID); Ulcusan® (ID); Ulis® (IT); Ulsikur® (ID); Ultec® (GB); Xepamet® (ID, SG); Zita® (GB)


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