Cimetidine
CLINICAL USE
H2 antagonist:Conditions associated with hyperacidity Refractory uraemic pruritus (unlicensed use)
DOSE IN NORMAL RENAL FUNCTION
Oral: duodenal and gastric ulceration treatment: 800 mg at night, or 400 mg twice daily; rarely, up to 1.6 g dailyProphylaxis: 400 mg at night or 400 mg twice dailyProphylaxis of stress ulceration: 200– 400 mg every 4–6 hoursReflux oesophagitis: 400 mg every 6 hours IM/IV: 200 mg every 4–6 hours, maximum 2.4 g dailyIV Infusion: 200–400 mg every 4–6 hours intermittent or 50–100 mg/hour continuous, maximum 2.4 g dailyZollinger-Ellison syndrome: 400 mg every 4–6 hours
PHARMACOKINETICS
DOSE IN RENAL IMPAIRMENT
GFR (mL/MIN)
DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugsAlpha-blockers: effects of tolazoline antagonisedAnti-arrhythmics: increased concentration of amiodarone, flecainide, lidocaine, procainamide and propafenoneAnticoagulants: enhanced effect of coumarinsAnti-epileptics: metabolism of carbamazepine, phenytoin and valproate inhibited. Antifungals: absorption of itraconazole and ketoconazole reduced; posaconazole concentration reduced; terbinafine concentration increasedAntimalarials: avoid concomitant use with artemether/lumefantrine; metabolism of chloroquine, hydroxychloroquine and quinine inhibitedAntipsychotics: possibly enhanced effect of antipsychotics, chlorpromazine and clozapine; increased risk of ventricular arrhythmias with sertindole – avoid concomitant useCiclosporin: possibly increased ciclosporin levelsCilostazol: possibly increased cilostazol concentration – avoid concomitant useCytotoxics: concentration of epirubicin and fluorouracil increased.156 CiMETidinEErgot alkaloids: increased risk of ergotism – avoid concomitant useTheophylline: metabolism of theophylline inhibited
ADMINISTRATION
Reconstition
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Route
Oral, IM, IV
Rate of Administration
IV Infusion: 400 mg in 100 mL sodium chloride 0.9% or glucose 5% over 30–60 minutesIV bolus: 200 mg over at least 5 minutes. Dilute larger doses to 10 mL and give over at least 10 minutesContinuous IV Infusion: 50–100 mg/hour
Comments
Avoid bolus if possible
OTHER INFORMATION
Inhibits tubular secretion of creatinine Uraemic patients susceptible to mental confusion