salbutamol

### Table of Contents

## salbutamol

also known as albuterol in USA.

see also pharmacology main index; asthma;

### actions

- beta 2 adrenergic agonist with beta 1 adrenergic activity (see sympathomimetics) which results in:
- bronchodilation hence used in Mx of asthma
- tachycardia
- tremors
- hypokalaemia from increased movement of K into cells
- hyperglycaemia
- may cause hypoxaemia in asthmatics by vasodilation of pulmonary vessels in unventilated alveoli resulting in V/Q mismatch
- tocolytic effect in obstetric labour ie. inhibits uterine contractions and thus used in Mx of premature labour, although this role has been largely replaced by the calcium channel blocker, nifedipine, which is better tolerated and orally administered.

### dosage

#### asthma

- see asthma
**inhaler:**- <20kg: 4–6 puffs (400–600 microg.) via spacer
- >20kg: 8–12 puffs (800–1200 microg.) via spacer
- usually given 4 hourly but in acute asthma can be given every 20min

**nebuliser:**- <20kg: 2.5mg made up to 4mL with normal saline nebulised with O2 8L per min
- >20kg: 5mg nebulised made up to 4mL with normal saline with O2 8L per min
- usually given 4 hourly but in acute asthma can be given every 20min
- can be used continuously undiluted if critical asthma episode:
- load 4mL of undiluted salbutamol nebuliser solution [5mg/mL] into nebuliser then run at 20mL/hr by infusion pump or repeatedly top up nebuliser with undiluted solution.

**iv infusion:**- use 50ml obstetric salbutamol solution (1mg/ml) undiluted
- determine base infusion rate for 1mcg/kg/min = wt x 0.06 ml/hr
- for those over 40kg, calculate as if 40kg
^{1)} **load dose**is 5-10mcg/kg/min for 1 hour = 5-10 x the base infusion rate calculated above- many give a load dose of 5mcg/kg over 10min
^{2)}but this is nonsensical if they then advise initial maintenance infusion rate of 5mcg/kg/min, titrated to 1-10mcg/kg/min

**maintenance rate**is 1-2mcg/kg/min = 1-2 x the base infusion rate calculated above

#### temporary Rx of hyperkalaemia

- 10-20mg in 4mls NSaline nebulised
- see hyperkalaemia

#### tocolytic in Rx of premature labour

^{1)},

^{2)}

salbutamol.txt · Last modified: 2012/01/17 04:05 by 127.0.0.1