Drug reference

Ranitidine

h2 Receptor Antagonist · Antiulcer

Also known as Ranitidine Hydrochloride

START

150 mg PO BID or 300 mg HS

TYPICAL MAX

600 mg/day (4 weeks)

STOP IF

Withdrawn — NDMA contamination · use famotidine instead

WATCH

If still prescribed: confusion in elderly · drug interactions

CDSCO bannedHATC A02BA02

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · acid suppression
PEAK: 2h · Cmax
t½: 2.5h · plasma t½
DURATION: 8h · single-dose effect

EXCRETION

70% renal unchanged · minimal CYP

route + CYP

INTERACTIONS

11 major

SEVERE in our sources

PREGNANCY

Category B — but largely withdrawn globally since 2020

FDA category + note

Top interactionssee all 12 →

AtazanavirSevereDatabaseDDInter
DasatinibSevereDatabaseDDInter
ItraconazoleSevereDatabaseDDInter
KetoconazoleSevereDatabaseDDInter

Available in India

277 branded formulations and 31 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Mechanism

Ranitidine selectively and reversibly blocks histamine H2 receptors located on the gastric parietal cells. This antagonism inhibits both basal and stimulated gastric acid secretion, primarily by reducing the volume and hydrogen ion concentration of gastric acid. It reduces acid secretion induced by histamine, gastrin, and acetylcholine.

Indications

Duodenal ulcer (active)Gastric ulcer (active)Gastroesophageal Reflux Disease (GERD)Erosive esophagitisZollinger-Ellison syndromeStress ulcer prophylaxis (off-label)Indigestion and heartburn reliefGastric ulcer (to promote healing)Duodenal ulcer (to promote healing)Gastroesophageal reflux disease (uncomplicated)Prevention of stress ulcersDuodenal ulcerGastric ulcerStress ulcers and gastritisGastroesophageal reflux disease (GERD) (mild or stage-1 cases)Prophylaxis of aspiration pneumoniaUrticaria (adjuvant to H1 antagonist)

Dosing

Adult: For duodenal/gastric ulcers: 150 mg PO BID or 300 mg PO HS for 4-8 weeks. For GERD: 150 mg PO BID. For Zollinger-Ellison: Initial 150 mg PO TID; can increase to 6 g/day. IV: 50 mg every 6-8 hours (slow IV push or infusion).
Pediatric: For GERD/ulcers (oral): 2-4 mg/kg/dose BID; max 300 mg/day. For infants 1 month to 16 years (IV): 1-2 mg/kg/dose every 6-8 hours; max 50 mg/dose.
Renal adjustment: CrCl <50 mL/min: Reduce dose by 50% (e.g., 150 mg PO daily or 50 mg IV daily). Use with caution in severe impairment. For hemodialysis patients, administer dose at the end of dialysis.
Hepatic adjustment: No specific dose adjustment recommended for mild to moderate hepatic impairment. Use with caution in severe hepatic dysfunction.
Geriatric: No specific dose adjustment needed based on age alone, but monitor renal function carefully due to age-related decline. Increased risk of CNS side effects (e.g., confusion).
Max dose: 300 mg/day for most indications; up to 6 g/day for Zollinger-Ellison syndrome under specialist supervision.

Pharmacokinetics

Onset

Oral: 30-60 minutes; IV: rapid

Peak effect

Oral: 1-3 hours; IV: within 15 minutes

Duration

6-12 hours

Half-life

2-3 hours (increases with renal impairment)

Bioavailability

~50%

Protein binding

Approximately 15%

Metabolism

Hepatic (minor, non-CYP-mediated), forming N-oxide, S-oxide, and desmethyl metabolites. Minimal first-pass metabolism.

Excretion

Primarily renal (unchanged drug, ~70% after IV, ~30% after oral). Minor fecal excretion.

Contraindications

Hypersensitivity to ranitidine or other H2-receptor antagonists
Acute porphyria (rare, historical consideration)
History of acute intermittent porphyria
Known allergy to other H2 blockers
Preparations withdrawn from use due to contamination issues
Rapid i.v. injection can cause hypotension

Side effects

Common

HeadacheNauseaDiarrheaConstipationDizzinessFatigueAbdominal discomfortDrowsinessMuscular painDiarrhoea/constipation

Serious

Bradycardia
CNS effects (e.g., confusion, hallucinations, depression, especially in elderly or renally impaired patients)
Hepatotoxicity (elevated LFTs, hepatitis, rare jaundice)
Blood dyscrasias (e.g., leukopenia, thrombocytopenia, agranulosis, aplastic anemia, rare)
Anaphylaxis or hypersensitivity reactions
Pancreatitis (rare)
Arrhythmias (IV administration)
CNS effects (confusion, delirium, hallucinations, slurred speech, headaches), primarily with IV administration or in elderly
Various blood disorders (e.g., thrombocytopenia)
Vitamin B12 deficiency

Pregnancy & lactation

Pregnancy

Category B — but largely withdrawn globally since 2020

Lactation

Ranitidine is excreted into breast milk. Although considered compatible with breastfeeding by some sources, caution is advised. Consult a physician.

Drug interactions

Atazanavir

Severe

Database

Decreased atazanavir plasma concentrations, leading to reduced antiviral efficacy and potential for viral resistance

Avoid co-administration. If an acid reducer is essential, consider alternative agents or administer ranitidine at least 2 hours after atazanavir, using the lowest effective dose.

Source: DDInter

Dasatinib

Severe

Database

Decreased dasatinib plasma concentrations, leading to reduced anti-cancer efficacy.

Avoid co-administration. If an acid reducer is necessary, consider alternative agents or separate administration by at least 2 hours.

Source: DDInter

Itraconazole

Severe

Database

Decreased antifungal efficacy, potential for treatment failure.

Avoid co-administration. If necessary, administer ranitidine at least 2 hours after itraconazole. Monitor for signs of treatment failure.