Ranitidine

Use

  1. Stress ulcer prophylaxis
  2. PUD
  3. GORD
  4. Dyspepsia

Presentation

50mg QID (IV)

150mg BD (PO)

Route/Dose

Clear solution for IV/IM 25mg/mL

150/300mg tablets

Syrup 15mg/mL

MoA

  • Inhibits gastric acid secretion
  • Competitive antagonist (actually an inverse agonist) of H2 receptors on Parietal Cells
  • Parietal cells secrete HCl & I.F
  • Histamine, ACh, Gastrin cells stimulate Parietal cells but histamine is most significant contributor because:
    1. Histamine blocks HCl secretion
    2. ↓volume of HCl secretion
  • Because ACh & gastric action is potentiated by histamine binding H2 receptor

PD

GI

  • ↓gastric acid secretion
  • ↑LES tone (dose related)

PK

A

OBA 60%

D

15% PPB, VD 1.2 – 1.8L/kg

M

Small % metabolised by oxidation & methylation

E

Mostly unchanged by kidney

t ½ 1.6 – 2.5hrs

Adverse Effects

  • Abnormal LFTs
  • Confusion
  • Thrombocytopaenia

NB: Cimetidine of same group has CYT P450 interactions, which causes anti-adrenergic & antidopaminergic actions