Salbutamol (albuterol) chemical structure, 2D skeletal formula, C13H21NO3

Salbutamol Chemical Structure

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1. Identification

Summary

Salbutamol (USAN: albuterol) is a short-acting β₂-adrenergic agonist (SABA) used for rapid bronchodilation in asthma, exercise-induced bronchospasm, and COPD; supplied mainly as the sulfate salt for inhalation, oral, and parenteral products.

Brand Names

Ventolin, ProAir, Proventil, Accuneb; numerous generics (region-dependent)

Name

Salbutamol (Albuterol)

Background

Racemic (R/S) catecholamine derivative introduced in the late 1960s; (R)-salbutamol is the active eutomer. Available as metered-dose inhalers, dry-powder inhalers, nebulizer solutions, oral tablets/syrup, and IV.

Modality

Small molecule

Groups

Approved; OTC/Rx status varies by jurisdiction and product

Structure

Salbutamol (albuterol) 2D chemical structure. Formula C13H21NO3; IUPAC long name; CAS 18559-94-9; UNII QF8SVZ843E.
Salbutamol (albuterol) chemical structure, 2D skeletal formula, C13H21NO3

Weight

≈ 239.31 g/mol (free base)

Chemical Formula

C₁₃H₂₁NO₃ (free base)

Synonyms

Albuterol; (RS)-4-[2-(tert-butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol

External IDs

CAS (base): 18559-94-9; CAS (sulfate): 51022-70-9
PubChem CID (base): 2083; UNII (base): QF8SVZ843E; UNII (sulfate): 021SEF3731
ATC: R03AC02; KEGG: D02147

2. Pharmacology

Indication

Relief and prevention of bronchospasm in asthma and COPD; exercise-induced bronchospasm prophylaxis; adjunct in hyperkalemia management (off-label protocols).

Associated Conditions

Acute asthma, intermittent asthma, COPD with reversible component, EIB.

Associated Therapies

Combined with inhaled corticosteroids for control; with ipratropium in some acute care settings.

Contraindications & Blackbox Warnings

No boxed warning. Contraindicated in severe hypersensitivity to components. Caution with significant cardiovascular disease, arrhythmias, seizure disorders, hyperthyroidism, and in patients on QT-prolonging agents.

Pharmacodynamics

Selective β₂-receptor agonism → ↑ cAMP in airway smooth muscle → bronchodilation, reduced mediator release, improved mucociliary clearance. Onset (inhaled) typically ≤15 min; duration 3–6 h.

Mechanism of action

Binds β₂-adrenergic receptors; Gs–adenylate cyclase activation increases cAMP; PKA-mediated phosphorylation lowers intracellular Ca²⁺ and relaxes bronchiolar smooth muscle.

Absorption

Inhaled: pulmonary + swallowed fractions; systemic exposure depends on device/technique. Oral: absorbed with first-pass metabolism; IV: immediate.

Volume of distribution

Large (order of ~2 L/kg), consistent with extensive tissue distribution.

Protein binding

Low (~10%).

Metabolism

Primarily hepatic to salbutamol 4′-O-sulfate (inactive); additional minor oxidative/conjugative routes.

Route of elimination

Predominantly renal as unchanged drug and sulfate conjugate; small fecal component.

Half-life

Inhaled ~4–6 h; oral ~5 h (formulation- and subject-dependent).

Clearance

Renal excretion of parent + metabolites; apparent clearance influenced by route, device, and co-medications.

Adverse Effects

Tremor, tachycardia, palpitations, nervousness, headache, hypokalemia, hyperglycemia, nausea. Rare: paradoxical bronchospasm, QT prolongation, serious arrhythmias.

Toxicity

Overdose → marked tachycardia, tremor, hypokalemia, lactic acidosis; management is supportive with monitoring of electrolytes and ECG.

Pathways

β₂-receptor signaling; hepatic sulfation; renal elimination.

Pharmacogenomic Effects/ADRs

Variants in ADRB2 (e.g., Gly16Arg) may modulate response in some cohorts; no routine PGx testing recommended.

3. Interactions

Drug Interactions

Nonselective β-blockers antagonize effect; MAO inhibitors/TCAs may potentiate cardiovascular effects; diuretics and other hypokalemia-inducing drugs increase hypokalemia risk; sympathomimetics add toxicity; caution with QT-prolonging agents.

Food Interactions

No clinically meaningful food effect on inhaled products; avoid excess caffeine if symptomatic tachycardia occurs.

4. Categories

ATC Codes

R03AC02 (selective β₂-agonists)

Drug Categories

Short-acting β₂-agonist; Bronchodilator; Small molecule

Chemical Taxonomy

Phenethylamine β-hydroxy scaffold; tert-butylamino side chain; phenolic diol motif.

Affected organisms

Humans (therapeutic use)

5. Chemical Identifiers

UNII

QF8SVZ843E (salbutamol, base); 021SEF3731 (salbutamol sulfate)

CAS number

18559-94-9 (base); 51022-70-9 (sulfate)

InChI Key

NDAUXUAQIAJITI-UHFFFAOYSA-N

InChI

InChI=1S/C13H21NO3/c1-13(2,3)14-7-12(17)9-4-5-11(16)10(6-9)8-15/h4-6,12,14-17H,7-8H2,1-3H3

IUPAC Name

(RS)-4-[2-(tert-butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol

SMILES

CC(C)(C)NCC(C1=CC(=C(C=C1)O)CO)O

6. References

PubChem Compound Summary: Salbutamol (CID 2083) — identifiers, formula, MW, canonical SMILES/InChI. PubChem
DailyMed labeling (albuterol sulfate) — UNII codes, dosage forms, PK (half-life ≈4–6 h), interactions, warnings. DailyMed+2DailyMed+2
FDA GSRS/UNII — albuterol sulfate 021SEF3731, formula and InChIKey; base UNII cross-reference. precision.fda.gov
ATC/DDD Index — R03AC02 salbutamol classification. ATCDDD
StatPearls/peer-reviewed PK — low protein binding (~10%), clinical use overview; bioavailability/half-life ranges corroborated across labels. NCBI+1

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