Respiratory/Short-acting β₂-agonist (SABA)

SABA

also: salbutamol · terbutaline · reliever · blue inhaler

Overview

The acute "reliever" bronchodilator. NOTE: under NG245 (2024), SABA-only treatment is NO LONGER recommended in asthma — but salbutamol remains central to acute attacks and COPD.

Mechanism

Selective β₂-adrenoceptor agonist → Gs → ↑cAMP → bronchial smooth-muscle relaxation (rapid onset, short duration). β₂ stimulation also drives K⁺ into cells.

Indications

Acute asthma / acute bronchospasm
Acute COPD exacerbation
Hyperkalaemia (nebulised — shifts K⁺ — cross-ref)

The agents

SalbutamolSABA

onset minutes, lasts 4–6 h

Inhaler/nebuliser; back-to-back nebs in acute severe asthma.

TerbutalineSABA

Alternative.

Adverse effects

Tremor, palpitations, tachycardiacommon

Hypokalaemiaserious

High-dose/nebulised — monitor K⁺ in acute severe asthma (esp. with steroids/aminophylline).

Lactic acidosis (high dose)common

Cautions & contraindications

SABA-only maintenance in asthmaall

NG245: associated with worse outcomes — use an ICS-containing reliever (AIR).

Overuse (>1 canister/month) = poor controlall

Marker of undertreated asthma.

Interactions

Additive hypokalaemia with theophylline, diuretics, steroids

Monitoring & kinetics

Inhaler technique; SABA use frequency (control marker); K⁺ in acute severe

Inhaled (spacer as effective as nebuliser in non-life-threatening attacks); nebulised/IV in severe.

Source: NICE NG245 — Asthma · BNF — Beta2-agonists