Atropine
Chemical
A naturally occurring tertiary amine, which is the ester of Tropic Acid and Tropine
NB: the ester is essential for binding at Ach R’s
Use
- Tx bradycardia
- Counter muscarinic effects of anticholinesterases
- Bronchodilation (nebulized)
Presentation
Clear, colourless ampoule; 600mcg/mL
Racemic → only (L) form has anticholinergic effects
Dose
300 – 600mcg
3mg for complete vagal blockade
Route
IM/IV
Onset
Rapid onset (1 min) – well matched to Edrophonium (when given at reversal of neuromuscular blockade)
DoA
Short 30 mins
MoA
Competitive antagonist at muscarinic cholinergic receptors
PD
CVS
- ↑HR
- ↑CO
- ↓AV conduction time
Resp
- Bronchodilation
- ↓bronchial secretions
CNS
- Central anticholinergic syndrome à somnolence, confusion, amnesia, agitation, delirium, mydriasis
GI
- ↓gastric secretions
- ↓salivation
- ↓gut tone & peristalsis
- Antispasmodic at biliary tree
- ↓LoS
PK
A
Rapidly absorbed; lipid soluble; 20% OBA
D
50% PPB
VD 2 – 4L/kg
Crosses BBB & placenta
M
Hydrolysed in liver & tissues to TROPINE + TROPIC ACID
E
95% dose excreted in 24hrs
Some unchanged
Adverse Effects
- Painful IM
- Dry mouth
- Inhibition of sweating à hyperpyrexia in elderly & children
- Elderly high risk of Central Anticholinergic Syndrome
- Glaucoma (↑ IOP)