Synthetic sympathomimetic amine

racemic mixture of the R- and S-isomers. The R-isomer has 150 times greater affinity for the beta2-receptor than the S-isomer and the S-isomer has been associated with toxicity

- Clear colourless solution containing 50-500mcg/ml after dilution for IV infusion
- Metered dose inhaler (100mcg) and dry powder (200-400mcg) for inhalation
- Clear colourless solution containing 2.5-5mg/ml for nebulization
- Oral preparation (syrup or tablets)

β2 agonist - GsPCR: Adenylate cyclase activated, cAMP

On cell membranes: ↑Na+/K+ ATPase activity and hyperpolarisation

Mild β1 agonist effects

CVS:
- At high doses, especially IV, B1 effects cause increased inotropy and chronotropy
- At lower doses, B2 effects predominate and may cause a decreased SVR due to skeletal muscle vasodilation
- May precipitate arrhythmias, particularly in the presence of hypokalaemia
Resp:
- Bronchodilation, leading to increased FEV1
- Interferes with hypoxic pulmonary vasoconstriction and may precipitate shunt leading to hypoxia
Metabolic/Other:
- Na/K/ATPase is stimulated and transports K into cells leading to hypokalaemia
- Increased blood glucose
- Beta adrenergic activity leads to increased production of lactate
- Tremor
Uterus:
- Relaxes gravid uterus
- 10% crosses the placenta and causes fetal tachycardia

Only weak protein binding

Vd (IV) 4-5L/kg

Converted by liver to inactive metabolite (esterified / oxidative deamination / conjugation with glucuronide)

Excreted urine as 40% free dug and 60% metabolite
Small amount in faeces

T1/2 5hrs

Appears to potentiate NDMR

Inh/Neb/IV

TOCOLYTIC

Level 3 for Tocolysis

Level 2 for Bronchodilation (see in relevant table)

synthetic sympathomimetic amine

uncomplicated preterm labour

(Asthma, COPD)

↑ myometrium cAMP (GsPCR) → increased cAMP → uterine SM relaxation

Fetal Tachycardia
Maternal Tachycardia/Palpitations/Arrhythmia,
tremors,
hypokalaemia, hyperlactataemia, hyperglycaemia.

IV infusion:
10mcg/minute and uptitrate slowly to 10mcg/min

Should not be used together with Nifedipine

BRONCHODILATORS - BETA AGONISTS

Level 2

short-acting, selective beta2-adrenergic receptor agonist used in the treatment of asthma and COPD.

(i) the symptomatic relief and prevention of bronchospasm due to bronchial asthma, chronic bronchitis, reversible obstructive airway disease, and other chronic bronchopulmonary disorders in which bronchospasm is a complicating factor, and/or (ii) the acute prophylaxis against exercise-induced bronchospasm and other stimuli known to induce bronchospasm

β2 agonist

- Anxiety, tremor, insomnia, restlessness
- Hypokalaemia
- Arrhythmias
- Lactic acidosis and ketosis

Inhalational / IV
BA 10%