Iptratropium

Chemical

A synthetic quaternary ammonium derivative of atropine → muscarinic antagonist

Use

Tx bronchoconstriction

Presentation

Solution, nebulised, aerosol inhalation

Route/Dose

Neb: 100 – 500mcg QID

Aerosol: 100 – 500mcg BD

Onset

Max effect in 1 – 2hrs

DoA

  • 20% pts have local effects
  • Dryness/unpleasant taste in mouth

Local deposition on eye → mydriasis & difficult with accommodation

MoA

Vagal parasymp. fibres provide bronchoconstrictor tone

Anticholinergic

  1. Competitively inhibits cholinergic receptors on bronchial smooth m.
    • M3 GPCR (Gq = phospholipase C pathway)
    • Inhibition of activation
    • ↓intrac. Ca2+
    • Bronchodilation

2. Inhibits cholinergic receptors of MCs & degranulation

PD

Resp – bronchodilation

CVS – ↑HR when given IV (anticholinergic); no effect inhaled

CNS – can’t cross BBB → quaternary ammonium

GU – @ large doses ↓gastric secretion & salivation

PK

A

30% (PO) & 5% (inhaled) reaches site of action

D

VD 0.4L/kg

M

8 inactive metabolites. By conjugation & hydrolysis

E

Metabolites via faeces & urine

Adverse Effects

  • 20% pts have local effects
  • Dryness/unpleasant taste in mouth
  • Local deposition on eye → mydriasis & difficult with accommodation