Gastroesophageal reflux disease: Oral: 400 mg 4 times daily or 800 mg twice daily for 12 weeks.
Heartburn (OTC labeling):
Prevention: Oral: 200 mg daily up to 30 minutes prior to eating foods or beverages that cause heartburn (maximum: 400 mg per 24 hours).
Relief of symptoms: Oral: 200 mg daily; maximum: 400 mg per 24 hours.
Interstitial cystitis (bladder pain syndrome) (off-label use): Oral: 200 mg 3 times daily or 300 to 400 mg twice daily (Dasgupta 2001; Seshadri 1994; Thilagarajah 2001).
Stress ulcer prophylaxis in critically ill patients (off-label use): Oral or NG tube: 300 mg 4 times daily (ASHP 1999). Note: Intended for patients with associated risk factors (eg, coagulopathy, mechanical ventilation for >48 hours, sepsis/septic shock); discontinue use once risk factors have resolved (Rhodes 2017).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Manufacturer's labeling:
Mild to moderate renal impairment: There are no dosage adjustments provided in the manufacturer’s labeling; use with caution.
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 recommendations (Aronoff 2007):
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
CRRT: 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 (specific dosage adjustment is not provided (Beers Criteria [AGS 2019]).
Stress ulcer prophylaxis in critically ill patients (off-label use): CrCl <30 mL/minute: 300 mg twice daily (ASHP 1999).
There are no dosage adjustments provided in the manufacturer’s labeling; use with caution. Dosage adjustments may be needed in patients with both renal and hepatic impairment.
(For additional information see "Cimetidine: Pediatric drug information")
Gastroesophageal reflux disease (GERD):
Infants, Children, and Adolescents <16 years: Limited data available: Oral: 20 to 40 mg/kg/day in 3 to 4 divided doses; maximum dose: 400 mg/dose (Cucchiara 1984; Cucchiara 1989; Lightdale 2013; NASPGHAN/ESPGHAN [Vandenplas 2009]). A pharmacokinetic modeling study suggests that the optimal dose for acid suppression is 10 mg/kg/dose every 6 hours and that some patients may need doses as high as 15 mg/kg/dose (Lambert 1992).
Adolescents ≥16 years: Oral: 400 mg 4 times daily or 800 mg twice daily for 12 weeks
Duodenal ulcer, treatment and maintenance:
Children ≥5 years and Adolescents <16 years: Limited data available, efficacy results variable: Oral: 20 to 40 mg/kg/day in 3 to 4 divided doses for 4 to 8 weeks, followed by 5 to 8 mg/kg/dose once daily at bedtime (Chiang 1989; Thomson 1983). In the largest trial, 33 patients (ages 8 to 15 years) with duodenal ulcer were allocated to receive cimetidine 20 mg/kg/day (n=8), an antacid (n=12), or sucralfate (n=17) for 8 weeks followed by maintenance therapy with once daily bedtime doses of cimetidine 5 mg/kg/dose, antacid, or sucralfate. Short-term improvement occurred in all three groups with no significant difference (Chiang 1989).
Adolescents ≥16 years: Oral: 300 mg 4 times daily or 800 mg at bedtime or 400 mg twice daily for up to 8 weeks
Duodenal ulcer, prophylaxis: Adolescents ≥16 years: Oral: 400 mg at bedtime
Gastric ulcer, active: Adolescents ≥16 years: Oral: 300 mg 4 times daily or 800 mg at bedtime for up to 8 weeks
Pathological hypersecretory conditions (eg, Zollinger-Ellison syndrome): Adolescents ≥16 years: Oral: 300 mg 4 times daily; adjust dose to patient response; maximum daily dose: 2,400 mg/day
Sour stomach/Heartburn (OTC labeling):
Prevention: Children ≥12 years and Adolescents: Oral: 200 mg daily up to 30 minutes prior to eating foods or beverages that cause heartburn (maximum daily dose: 400 mg/24 hours)
Relief of symptoms: Children ≥12 years and Adolescents: Oral: 200 mg daily; maximum daily dose: 400 mg/24 hours
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Manufacturer's labeling: Adolescents ≥16 years:
Mild to moderate renal impairment: There are no dosage adjustments provided in the manufacturer’s labeling; use with caution.
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.
Adolescents ≥16 years: There are no dosage adjustments provided in the manufacturer’s labeling; use with caution. Dosage adjustments may be needed in patients with both renal and hepatic impairment.
Refer to adult dosing.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Oral, as hydrochloride [strength expressed as base]:
Generic: 400 mg/6.67 mL (6.67 mL); 300 mg/5 mL (5 mL, 237 mL)
Tablet, Oral:
Cimetidine Acid Reducer: 200 mg
Generic: 200 mg, 300 mg, 400 mg, 800 mg
Yes
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Oral, as hydrochloride [strength expressed as base]:
Generic: 300 mg/5 mL (250 mL)
Tablet, Oral:
Generic: 200 mg, 300 mg, 400 mg, 600 mg, 800 mg
Oral: Administer with meals. For stress ulcer prophylaxis in critically-ill patients (off-label use), may administer via NG tube (Rhodes 2017).
Oral: Administer with food; do not administer simultaneously with antacids
Gastroesophageal reflux disease: Treatment of erosive gastroesophageal reflux disease.
Heartburn (OTC only): Relief and prevention of heartburn associated with acid indigestion and sour stomach.
Interstitial cystitis/bladder pain syndrome; Stress ulcer prophylaxis in critically-ill patients
Cimetidine may be confused with simethicone
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
1% to 10%:
Central nervous system: Headache (2% to 4%), dizziness (1%), drowsiness (1%)
Endocrine & metabolic: Gynecomastia (≤4%)
Gastrointestinal: Diarrhea (1%)
Frequency not defined: Renal: Increased serum creatinine
Postmarketing: Agitation, agranulocytosis, alopecia, anaphylaxis, anxiety, aplastic anemia, arthralgia, confusion, decreased white blood cell count, depression, disorientation, fever (Potter 1986), hallucination, hemolytic anemia (immune-based), hepatic fibrosis, hypersensitivity angiitis, hypersensitivity reaction, hypotension, impotence (Jensen 1983), increased serum transaminases, interstitial nephritis, myalgia, pancreatitis, pancytopenia, polymyositis (Watson 1983), psychosis, urinary retention, thrombocytopenia
Hypersensitivity to cimetidine or any component of the formulation
OTC labeling: When used for self-medication (OTC), do not use if trouble or pain when swallowing food, vomiting with blood, or bloody or black stools, allergic to cimetidine or other acid reducers. Do not use with other acid reducers.
Documentation of allergenic cross-reactivity for histamine H2 antagonists is limited. However, because of similarities in chemical structure and/or pharmacologic actions, the possibility of cross-sensitivity cannot be ruled out with certainty.
Concerns related to adverse effects:
• Confusion: Rare cases of reversible confusion have been associated with cimetidine; usually in elderly or severely ill patients, or in patients with renal or hepatic impairment.
• Vitamin B12 deficiency: Prolonged treatment (≥2 years) may lead to vitamin B12 malabsorption and subsequent vitamin B12 deficiency. The magnitude of the deficiency is dose-related and the association is stronger in females and those younger in age (<30 years); prevalence is decreased after discontinuation of therapy (Lam 2013).
Disease-related concerns:
• Gastric malignancy: Relief of symptoms does not preclude the presence of a gastric malignancy.
• Hepatic impairment: Use with caution in patients with hepatic impairment.
• Renal impairment: Use with caution in patients with renal impairment; dosage adjustment recommended.
Special populations:
• Elderly: Use caution in this age group due to risk of confusion and other CNS effects. Cimetidine should be avoided in those older adults with, or at risk of, delirium.
• Immunocompromised patients: May have increased risk of hyperinfection of strongyloidiasis.
• Pediatric: Use of gastric acid inhibitors, including proton pump inhibitors and H2 blockers, has been associated with an increased risk for development of acute gastroenteritis and community-acquired pneumonia in pediatric patients (Canani 2006).
Other warnings/precautions:
• Serum creatinine/creatinine clearance estimates: Cimetidine can cause a transient and reversible rise in serum creatinine and/or decrease in creatinine clearance (when using routine creatinine clearance estimation formulas). This interference is likely due to competitive inhibition of cimetidine with creatinine for active tubular secretion and independent of an actual change in glomerular filtration rate (GFR). In patients with normal renal function, the rise in serum creatinine may not be clinically apparent, but in patients with varying degrees of renal impairment, this rise in serum creatinine may be more significant. Thus, treatment with cimetidine in patients with renal failure may invalidate measurements of serum creatinine and estimates of creatinine clearance (Andreev 1999; Larsson 1980). However, creatinine clearance estimation formulas, such as Cockcroft-Gault, are known to overestimate actual GFR, particularly in patients with renal impairment, and use of cimetidine has been explored clinically to improve the accuracy of creatinine clearance estimates in these patients (Choi 1993; Van Acker 1992).
• OTC labeling: When used for self-medication (OTC), notify health care provider before use if any of the following are present: Frequent chest pain; frequent wheezing particularly with heartburn; nausea/vomiting; unexplained weight loss; stomach pain; heartburn >3 months; heartburn with light-headedness, sweating, or dizziness; chest pain or shoulder pain with shortness of breath; sweating or pain that spreads to arms, neck, or shoulders; light-headedness. Stop use and notify health care provider if heartburn continues or worsens, stomach pain continues, or if use is required >14 days.
Use of gastric acid inhibitors, including proton pump inhibitors and H2 blockers, has been associated with an increased risk for development of acute gastroenteritis and community-acquired pneumonia in pediatric patients (Canani 2006). A large epidemiological study has suggested an increased risk for developing pneumonia in patients receiving H2 receptor antagonists; however, a causal relationship with cimetidine has not been demonstrated. A cohort analysis including over 11,000 neonates reported an association of H2 blocker use and an increased incidence of NEC in VLBW neonates (Guillet 2006). An approximate sixfold increase in mortality, NEC, and infection (ie, sepsis, pneumonia, UTI) was reported in patients receiving another H2 blocker, ranitidine, in a cohort analysis of 274 VLBW neonates (Terrin 2011).
Substrate of OAT1/3, OCT2, P-glycoprotein/ABCB1 (minor); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential; Inhibits CYP1A2 (weak), CYP2C19 (weak), CYP2D6 (weak), CYP3A4 (weak)
Acalabrutinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Acalabrutinib. Management: To minimize the potential for a significant interaction, separate administration of these agents by giving acalabrutinib 2 hours before ingestion of a histamine-2 receptor antagonist. Risk D: Consider therapy modification
Alfentanil: Cimetidine may increase the serum concentration of Alfentanil. Risk C: Monitor therapy
ALPRAZolam: CYP3A4 Inhibitors (Weak) may increase the serum concentration of ALPRAZolam. Risk C: Monitor therapy
Amiodarone: Cimetidine may increase the serum concentration of Amiodarone. Risk X: Avoid combination
Atazanavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Atazanavir. Management: Specific dose limitations and administration guidelines exist; consult full interaction monograph or atazanavir prescribing information. Risk D: Consider therapy modification
AtorvaSTATin: Cimetidine may enhance the adverse/toxic effect of AtorvaSTATin. Specifically, there is a theoretical potential for enhanced effects on reducing endogenous steroid activity. Risk C: Monitor therapy
Azelastine (Systemic): Cimetidine may increase the serum concentration of Azelastine (Systemic). Risk C: Monitor therapy
Belumosudil: Histamine H2 Receptor Antagonists may decrease the serum concentration of Belumosudil. Risk C: Monitor therapy
Bosutinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Bosutinib. Management: Administer histamine H2 receptor antagonists more than 2 hours before or after bosutinib. Risk D: Consider therapy modification
Bromazepam: Cimetidine may increase the serum concentration of Bromazepam. Risk C: Monitor therapy
Calcium Channel Blockers: Cimetidine may increase the serum concentration of Calcium Channel Blockers. Risk C: Monitor therapy
CarBAMazepine: CYP3A4 Inhibitors (Weak) may increase the serum concentration of CarBAMazepine. Risk C: Monitor therapy
Carmustine: Cimetidine may enhance the myelosuppressive effect of Carmustine. Management: Consider alternatives to cimetidine in patients receiving carmustine. If the combination cannot be avoided, monitor for enhanced carmustine myelotoxicity. Risk D: Consider therapy modification
Carvedilol: Cimetidine may increase the serum concentration of Carvedilol. Risk C: Monitor therapy
Cefditoren: Histamine H2 Receptor Antagonists may decrease the serum concentration of Cefditoren. Management: Concomitant use of cefditoren with H2-antagonists and antacids is not recommended. Consider alternative methods to control acid reflux (eg, diet modification) or alternative antimicrobial therapy if use of H2-antagonists can not be avoided. Risk D: Consider therapy modification
Cefpodoxime: Histamine H2 Receptor Antagonists may decrease the serum concentration of Cefpodoxime. Risk C: Monitor therapy
Cefuroxime: Histamine H2 Receptor Antagonists may decrease the absorption of Cefuroxime. Separate oral doses by at least 2 hours. Risk X: Avoid combination
Chlormethiazole: Cimetidine may increase the serum concentration of Chlormethiazole. Risk C: Monitor therapy
Chloroquine: Cimetidine may increase the serum concentration of Chloroquine. Risk X: Avoid combination
Cisapride: Cimetidine may increase the serum concentration of Cisapride. Management: Consider alternatives to cimetidine. If this combination cannot be avoided, monitor for toxic effects of cisapride if cimetidine is initiated/dose increased, or decreased efficacy if cimetidine is discontinued/dose decreased. Risk D: Consider therapy modification
Citalopram: Cimetidine may increase the serum concentration of Citalopram. Management: Limit citalopram dose to a maximum of 20 mg/day if used with cimetidine. Patients using this combination should be monitored closely for evidence of citalopram toxicity (eg, serotonin syndrome, QT prolongation). Risk D: Consider therapy modification
CloBAZam: CYP2C19 Inhibitors (Weak) may increase serum concentrations of the active metabolite(s) of CloBAZam. CYP2C19 Inhibitors (Weak) may increase the serum concentration of CloBAZam. Risk C: Monitor therapy
CloZAPine: Cimetidine may increase the serum concentration of CloZAPine. Risk C: Monitor therapy
CycloSPORINE (Systemic): CYP3A4 Inhibitors (Weak) may increase the serum concentration of CycloSPORINE (Systemic). Risk C: Monitor therapy
Cysteamine (Systemic): Histamine H2 Receptor Antagonists may diminish the therapeutic effect of Cysteamine (Systemic). Risk C: Monitor therapy
Dacomitinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Dacomitinib. Management: Administer dacomitinib at least 6 hours before or 10 hours after an histamine H2-receptor antagonist (H2RA). Risk D: Consider therapy modification
Dalfampridine: Cimetidine may increase the serum concentration of Dalfampridine. Management: The potential benefits of taking cimetidine concurrently with dalfampridine should be considered against the risk of seizures in these patients. Some non-US labeling contraindicates the use of dalfampridine with cimetidine. Risk D: Consider therapy modification
Dasatinib: Histamine H2 Receptor Antagonists may decrease the absorption of Dasatinib. Management: Antacids (taken 2 hours before or after dasatinib administration) can be used in place of H2-antagonists if some acid-reducing therapy is needed. Risk X: Avoid combination
Delavirdine: Histamine H2 Receptor Antagonists may decrease the serum concentration of Delavirdine. Risk X: Avoid combination
Dofetilide: Cimetidine may increase the serum concentration of Dofetilide. This is likely via inhibition of dofetilide renal tubular secretion (primarily) and inhibition of dofetilide metabolism. Risk X: Avoid combination
Doxofylline: Cimetidine may increase the serum concentration of Doxofylline. Risk C: Monitor therapy
Enoxacin: Cimetidine may increase the serum concentration of Enoxacin. Cimetidine may decrease the serum concentration of Enoxacin. Risk C: Monitor therapy
EpiRUBicin: Cimetidine may increase the serum concentration of EpiRUBicin. Risk X: Avoid combination
Erdafitinib: May increase the serum concentration of OCT2 Substrates. Risk C: Monitor therapy
Erlotinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Erlotinib. Management: Avoid H2-antagonists in patients receiving erlotinib when possible. If concomitant treatment cannot be avoided, erlotinib should be dosed once daily, 10 hours after and at least 2 hours before H2-antagonist dosing. Risk D: Consider therapy modification
Erythromycin (Systemic): Cimetidine may increase the serum concentration of Erythromycin (Systemic). Risk C: Monitor therapy
Escitalopram: Cimetidine may increase the serum concentration of Escitalopram. Risk C: Monitor therapy
Fexinidazole: May increase the serum concentration of OAT1/3 Substrates (Clinically Relevant). Management: Avoid use of fexinidazole with OAT1/3 substrates when possible. If combined, monitor for increased OAT1/3 substrate toxicities. Risk D: Consider therapy modification
Fexinidazole: May increase the serum concentration of OCT2 Substrates. Management: Avoid use of fexinidazole with OCT2 substrates when possible. If combined, monitor for increased OCT2 substrate toxicities. Risk D: Consider therapy modification
Finerenone: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Finerenone. Risk C: Monitor therapy
Flibanserin: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Flibanserin. Risk C: Monitor therapy
Flunitrazepam: Cimetidine may increase the serum concentration of Flunitrazepam. Risk C: Monitor therapy
Fluorouracil Products: Cimetidine may increase the serum concentration of Fluorouracil Products. Risk C: Monitor therapy
FLUoxetine: Cimetidine may increase the serum concentration of FLUoxetine. Risk C: Monitor therapy
Fosamprenavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Fosamprenavir. Cimetidine may also inhibit the metabolism of the active metabolite amprenavir, making its effects on fosamprenavir/amprenavir concentrations difficult to predict. Risk C: Monitor therapy
Fosphenytoin-Phenytoin: Cimetidine may enhance the adverse/toxic effect of Fosphenytoin-Phenytoin. Cimetidine may increase the serum concentration of Fosphenytoin-Phenytoin. Management: Consider using an alternative H2-antagonist to avoid this interaction. Monitor for toxic effects of hydantoin antiseizure drugs if cimetidine is initiated/dose increased. Risk D: Consider therapy modification
Gefitinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Gefitinib. Management: Administer gefitinib at least 6 hours before or 6 hours after administration of a histamine H2 receptor antagonist (H2RA), and closely monitor clinical response to gefitinib. Risk D: Consider therapy modification
Hydroxychloroquine: Cimetidine may increase the serum concentration of Hydroxychloroquine. Risk X: Avoid combination
Indinavir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Indinavir. Risk C: Monitor therapy
Infigratinib: Histamine H2 Receptor Antagonists may decrease serum concentrations of the active metabolite(s) of Infigratinib. Histamine H2 Receptor Antagonists may decrease the serum concentration of Infigratinib. Management: Avoid coadministration of infigratinib with histamine receptor antagonists (H2RAs) or other gastric acid-lowering agents. If H2RAs cannot be avoided, administer infigratinib 2 hours before or 10 hours after administration of H2RAs. Risk D: Consider therapy modification
Itraconazole: Histamine H2 Receptor Antagonists may increase the serum concentration of Itraconazole. Histamine H2 Receptor Antagonists may decrease the serum concentration of Itraconazole. Management: Administer Sporanox brand itraconazole at least 2 hours before or 2 hours after administration of any histamine H2 receptor antagonists (H2RAs). Exposure to Tolsura brand itraconazole may be increased by H2RAs; consider itraconazole dose reduction. Risk D: Consider therapy modification
Ixabepilone: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Ixabepilone. Risk C: Monitor therapy
Ketoconazole (Systemic): Histamine H2 Receptor Antagonists may decrease the serum concentration of Ketoconazole (Systemic). Management: Administer oral ketoconazole at least 2 hours prior to use of any H2-receptor antagonist. Monitor patients closely for signs of inadequate clinical response to ketoconazole. Risk D: Consider therapy modification
Ledipasvir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Ledipasvir. Management: Administer H2 receptor antagonist doses less than or comparable to famotidine 40 mg twice daily simultaneously or 12 hours prior to ledipasvir. The effect of administering H2 receptor antagonists at other time intervals is unknown and not recommended. Risk D: Consider therapy modification
Lemborexant: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Lemborexant. Management: The maximum recommended dosage of lemborexant is 5 mg, no more than once per night, when coadministered with weak CYP3A4 inhibitors. Risk D: Consider therapy modification
Levoketoconazole: Histamine H2 Receptor Antagonists may decrease the absorption of Levoketoconazole. Risk X: Avoid combination
Lidocaine (Systemic): Cimetidine may increase the serum concentration of Lidocaine (Systemic). Risk C: Monitor therapy
Lidocaine (Topical): Cimetidine may increase the serum concentration of Lidocaine (Topical). Risk C: Monitor therapy
Lomitapide: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Lomitapide. Management: Patients on lomitapide 5 mg/day may continue that dose. Patients taking lomitapide 10 mg/day or more should decrease the lomitapide dose by half. The lomitapide dose may then be titrated up to a max adult dose of 30 mg/day. Risk D: Consider therapy modification
Lonafarnib: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Lonafarnib. Management: Avoid concurrent use of lonafarnib with weak CYP3A4 inhibitors. If concurrent use is unavoidable, reduce the lonafarnib dose to or continue at a dose of 115 mg/square meter. Monitor for evidence of arrhythmia, syncope, palpitations, or similar effects. Risk D: Consider therapy modification
Mebendazole: Cimetidine may increase the serum concentration of Mebendazole. Risk C: Monitor therapy
Melatonin: Cimetidine may increase the serum concentration of Melatonin. Risk C: Monitor therapy
Meperidine: Cimetidine may increase the serum concentration of Meperidine. Risk C: Monitor therapy
MetFORMIN: Cimetidine may increase the serum concentration of MetFORMIN. Management: Consider alternatives to cimetidine in patients receiving metformin due to a potential for increased metformin concentrations and toxicity (including lactic acidosis). Risk D: Consider therapy modification
Midazolam: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Midazolam. Risk C: Monitor therapy
Mirtazapine: Cimetidine may increase the serum concentration of Mirtazapine. Risk C: Monitor therapy
Moclobemide: Cimetidine may increase the serum concentration of Moclobemide. Management: Consider using alternative agents to increase gastric pH in order to avoid this interaction. If combined, a moclobemide dose reduction of 50% may be necessary, and patients should be monitored for increased moclobemide effects/toxicities. Risk D: Consider therapy modification
Multivitamins/Minerals (with ADEK, Folate, Iron): Histamine H2 Receptor Antagonists may decrease the serum concentration of Multivitamins/Minerals (with ADEK, Folate, Iron). Specifically, the absorption of iron may be impaired by H2-antagonists. Risk C: Monitor therapy
Nelfinavir: Histamine H2 Receptor Antagonists may decrease serum concentrations of the active metabolite(s) of Nelfinavir. Histamine H2 Receptor Antagonists may decrease the serum concentration of Nelfinavir. Concentrations of the active M8 metabolite may also be reduced. Risk C: Monitor therapy
Neratinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Neratinib. Specifically, histamine H2 receptor antagonists may reduce neratinib absorption. Management: Administer neratinib at least 2 hours before or 10 hours after administration of a histamine H2 receptor antagonist to minimize the impact of this interaction. Risk D: Consider therapy modification
Nicotine: Cimetidine may increase the serum concentration of Nicotine. Risk C: Monitor therapy
Nilotinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Nilotinib. Management: The nilotinib dose should be given 10 hours after or 2 hours before the H2 receptor antagonist in order to minimize the risk of a significant interaction. Risk D: Consider therapy modification
NiMODipine: CYP3A4 Inhibitors (Weak) may increase the serum concentration of NiMODipine. Risk C: Monitor therapy
Nitisinone: May increase the serum concentration of OAT1/3 Substrates (Clinically Relevant). Risk C: Monitor therapy
Octreotide: Histamine H2 Receptor Antagonists may decrease the serum concentration of Octreotide. Risk C: Monitor therapy
PARoxetine: Cimetidine may increase the serum concentration of PARoxetine. Risk C: Monitor therapy
PAZOPanib: Histamine H2 Receptor Antagonists may decrease the serum concentration of PAZOPanib. Risk X: Avoid combination
Pentoxifylline: Cimetidine may increase the serum concentration of Pentoxifylline. Risk C: Monitor therapy
Pexidartinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Pexidartinib. Management: Administer pexidartinib 2 hours before or 10 hours after histamine H2 receptor antagonists. Risk D: Consider therapy modification
Pilsicainide: Cimetidine may increase the serum concentration of Pilsicainide. Risk C: Monitor therapy
Pimozide: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Pimozide. Risk X: Avoid combination
Posaconazole: Histamine H2 Receptor Antagonists may decrease the serum concentration of Posaconazole. Management: Avoid concurrent use of oral suspension with H2-antagonists whenever possible. Monitor patients closely for decreased antifungal effects if this combination is used. Delayed-release posaconazole tablets may be less likely to interact. Risk D: Consider therapy modification
Pramipexole: Cimetidine may increase the serum concentration of Pramipexole. Risk C: Monitor therapy
Praziquantel: Cimetidine may increase the serum concentration of Praziquantel. Risk C: Monitor therapy
Pretomanid: May increase the serum concentration of OAT1/3 Substrates (Clinically Relevant). Risk C: Monitor therapy
Procainamide: Cimetidine may increase the serum concentration of Procainamide. Management: Consider an alternative H2-receptor antagonist in patients taking procainamide. If combined, monitor for increased therapeutic effects/toxicity of procainamide. Risk D: Consider therapy modification
QuiNIDine: Cimetidine may increase the serum concentration of QuiNIDine. Management: Consider alternatives to cimetidine. If the combination cannot be avoided, monitor for increased quinidine concentrations/toxicity with cimetidine initiation/dose increase, or decreased concentrations/effects with cimetidine discontinuation/dose decrease. Risk D: Consider therapy modification
QuiNINE: Cimetidine may increase the serum concentration of QuiNINE. Management: Consider using an alternative H2-receptor antagonist (eg, ranitidine) instead of cimetidine due to a lower interaction risk. If combined, monitor patients closely for signs and symptoms of quinine toxicity. Risk D: Consider therapy modification
Rilpivirine: Histamine H2 Receptor Antagonists may decrease the serum concentration of Rilpivirine. Management: Administer histamine H2 receptor antagonists at least 12 hours before or 4 hours after rilpivirine. Risk D: Consider therapy modification
Risedronate: Histamine H2 Receptor Antagonists may increase the serum concentration of Risedronate. This applies specifically to delayed-release risedronate. Risk X: Avoid combination
Roflumilast: Cimetidine may increase serum concentrations of the active metabolite(s) of Roflumilast. Cimetidine may increase the serum concentration of Roflumilast. Risk C: Monitor therapy
Saquinavir: Histamine H2 Receptor Antagonists may increase the serum concentration of Saquinavir. Risk C: Monitor therapy
Secretin: Histamine H2 Receptor Antagonists may diminish the diagnostic effect of Secretin. Specifically, use of H2-Antagonists may cause a hyperresponse in gastrin secretion in response to secretin stimulation testing, falsely suggesting gastrinoma. Management: Avoid concomitant use of histamine H2-antagonists (H2RAs) and secretin. Discontinue H2RAs at least 2 days prior to secretin administration. Risk D: Consider therapy modification
Selpercatinib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Selpercatinib. Management: Coadministration of selpercatinib and H2 receptor antagonists should be avoided. If coadministration cannot be avoided, selpercatinib should be administered 2 hours before or 10 hours after H2 receptor antagonists. Risk D: Consider therapy modification
Simvastatin: CYP3A4 Inhibitors (Weak) may increase serum concentrations of the active metabolite(s) of Simvastatin. CYP3A4 Inhibitors (Weak) may increase the serum concentration of Simvastatin. Risk C: Monitor therapy
Sirolimus (Conventional): CYP3A4 Inhibitors (Weak) may increase the serum concentration of Sirolimus (Conventional). Risk C: Monitor therapy
Sirolimus (Protein Bound): CYP3A4 Inhibitors (Weak) may increase the serum concentration of Sirolimus (Protein Bound). Management: Reduce the dose of protein bound sirolimus to 56 mg/m2 when used concomitantly with a weak CYP3A4 inhibitor. Risk D: Consider therapy modification
Sotorasib: Histamine H2 Receptor Antagonists may decrease the serum concentration of Sotorasib. Risk X: Avoid combination
Sulfonylureas: Cimetidine may increase the serum concentration of Sulfonylureas. Risk C: Monitor therapy
Tacrolimus (Systemic): CYP3A4 Inhibitors (Weak) may increase the serum concentration of Tacrolimus (Systemic). Risk C: Monitor therapy
Tafenoquine: May increase the serum concentration of OCT2 Substrates. Management: Avoid use of OCT2 substrates with tafenoquine, and if the combination cannot be avoided, monitor closely for evidence of toxicity of the OCT2 substrate and consider a reduced dose of the OCT2 substrate according to that substrate's labeling. Risk D: Consider therapy modification
Tamsulosin: Cimetidine may increase the serum concentration of Tamsulosin. Risk C: Monitor therapy
Teriflunomide: May increase the serum concentration of OAT1/3 Substrates (Clinically Relevant). Risk C: Monitor therapy
Theophylline Derivatives: CYP1A2 Inhibitors (Weak) may increase the serum concentration of Theophylline Derivatives. Risk C: Monitor therapy
Thioridazine: CYP2D6 Inhibitors (Weak) may increase the serum concentration of Thioridazine. Management: Consider avoiding concomitant use of thioridazine and weak CYP2D6 inhibitors. If combined, monitor closely for QTc interval prolongation and arrhythmias. Some weak CYP2D6 inhibitors list use with thioridazine as a contraindication. Risk D: Consider therapy modification
TiZANidine: CYP1A2 Inhibitors (Weak) may increase the serum concentration of TiZANidine. Management: Avoid these combinations when possible. If combined use is necessary, initiate tizanidine at an adult dose of 2 mg and increase in 2 to 4 mg increments based on patient response. Monitor for increased effects of tizanidine, including adverse reactions. Risk D: Consider therapy modification
Triazolam: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Triazolam. Risk C: Monitor therapy
Tricyclic Antidepressants: Cimetidine may decrease the metabolism of Tricyclic Antidepressants. Risk C: Monitor therapy
Ubrogepant: CYP3A4 Inhibitors (Weak) may increase the serum concentration of Ubrogepant. Management: In patients taking weak CYP3A4 inhibitors, the initial and second dose (given at least 2 hours later if needed) of ubrogepant should be limited to 50 mg. Risk D: Consider therapy modification
Urapidil: Cimetidine may enhance the hypotensive effect of Urapidil. Risk C: Monitor therapy
Velpatasvir: Histamine H2 Receptor Antagonists may decrease the serum concentration of Velpatasvir. Risk C: Monitor therapy
Vitamin K Antagonists (eg, warfarin): Cimetidine may enhance the anticoagulant effect of Vitamin K Antagonists. Management: Avoid coadministration of cimetidine and vitamin K antagonists. If unavoidable, monitor for increased effects of vitamin K antagonists when cimetidine is initiated/dose increased, or decreased effects if cimetidine is discontinued/dose decreased. Risk D: Consider therapy modification
Zaleplon: Cimetidine may increase the serum concentration of Zaleplon. Management: The initial dose of zaleplon should be limited to 5 mg in patients taking cimetidine. Monitor patients for increased zaleplon effects/toxicities (ie, sedation, CNS depression) when these agents are combined. Risk D: Consider therapy modification
ZOLMitriptan: Cimetidine may increase the serum concentration of ZOLMitriptan. Management: Limit the maximum single dose of zolmitriptan to 2.5 mg, not to exceed 5 mg in 24 hours, when coadministered with cimetidine. Risk D: Consider therapy modification
Prolonged treatment (≥2 years) may lead to malabsorption of dietary vitamin B12 and subsequent vitamin B12 deficiency (Lam 2013).
Cimetidine crosses the placenta (Howe 1981). Histamine H2 antagonists have been evaluated for the treatment of gastroesophageal reflux disease (GERD), as well as gastric and duodenal ulcers during pregnancy (Cappell 2003; Richter 2003). Histamine H2 antagonists may be used for aspiration prophylaxis prior to cesarean delivery (ASA 2007).
Cimetidine is excreted in breast milk. Breastfeeding is not recommended by the manufacturer.
CBC, gastric pH; monitor renal function to correct dose; occult blood with GI bleeding; signs of confusion.
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
Onset of action: 1 hour
Duration: 80% reduction in gastric acid secretion for 4 to 5 hours after 300 mg dose
Absorption: Rapid
Distribution: Children and Adolescents: 1.23 ± 0.45 L/kg (Lloyd 1985b); Adults: 1 to 1.5 L/kg (Somogyi 1983)
Protein binding: 20% (Somogyi 1983)
Metabolism: Partially hepatic, forms metabolites (Somogyi 1983)
Bioavailability: ~60% to 70% (Somogyi 1983)
Half-life elimination: Neonates: 3.6 hours (Lloyd 1985a); Children and Adolescents: 1.39 ± 0.25 hours (Lloyd 1985b); Adults: ~2 hours
Time to peak, serum: Oral: 0.75 to 1.5 hours
Excretion: Primarily urine (48% as unchanged drug); feces (2%) (Somogyi 1983)
Renal function impairment: Drug accumulation may occur in patients with severe renal failure.
Solution (Cimetidine HCl Oral)
300 mg/5 mL (per mL): $0.42
Tablets (Cimetidine Oral)
200 mg (per each): $1.55
300 mg (per each): $1.61 - $2.05
400 mg (per each): $2.61 - $3.34
800 mg (per each): $5.02 - $6.20
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
