Albuterol, called salbutamol outside the US, is a short-acting beta-2 adrenergic agonist. It is one of the most widely used asthma drugs in the world, best known as the blue “rescue” inhaler (Ventolin HFA and generics). It is also sold as oral tablets. It is not a steroid or a hormone.

In the US it is approved to relieve and prevent bronchospasm (narrowing of the airways) in reversible obstructive airway disease, and to prevent exercise-induced bronchospasm. Outside medicine, oral albuterol is used in gyms as a milder relative of clenbuterol, for muscle and fat-loss effects. Controlled trials in healthy young men show that high oral doses can add lean mass during resistance training, but they did not reduce fat mass and came with measurable cardiac and fitness trade-offs.

This page summarizes what the FDA labels, clinical trials and the World Anti-Doping Agency (WADA) report. It is for education only and is not medical advice.

Property	Detail
Drug class	Selective short-acting beta-2 adrenergic agonist (sympathomimetic bronchodilator); not a steroid
Other name	Salbutamol (WHO international name)
Brands / US approval	Ventolin HFA (GSK, NDA 020983; initial US approval 1981); ProAir and many generics
Routes	Oral inhalation (metered-dose inhaler, powder inhaler, nebulizer solution); oral tablets
Strengths	Inhaler 90 µg albuterol base per actuation; tablets 2 mg and 4 mg
Half-life (labels)	About 5 h after a 4 mg tablet; about 4.6 h after inhalation
Mechanism	Activates beta-2 receptors, raising cyclic AMP and relaxing airway smooth muscle
US status	Prescription only; not listed in Schedule III
WADA status	Prohibited at all times (S3); inhaled salbutamol allowed up to 1,600 µg per 24 h, max 600 µg per 8 h

What it is

Albuterol’s chemical name is 4-[2-(tert-butylamino)-1-hydroxyethyl]-2-(hydroxymethyl)phenol: formula C₁₃H₂₁NO₃, molecular weight 239.31 g/mol (PubChem). Medicines contain it as albuterol sulfate, and doses are stated as albuterol base. A 4 mg tablet contains 4.8 mg of the sulfate salt (albuterol tablets label).

The tablet label describes several key features:

it is the racemic form, a 50:50 mix of two mirror-image molecules;
it acts preferentially on beta-2 receptors, the main adrenergic receptor type in bronchial smooth muscle;
beta-2 receptors also make up an estimated 10–50% of the beta receptors in the human heart, so even a “selective” beta-2 agonist can affect heart rate and rhythm;
it lasts longer than older drugs such as isoproterenol because it is not broken down by catechol-O-methyltransferase or taken up by catecholamine transporters.

Receptor activation raises cyclic AMP (cAMP) inside the cell. In airway muscle this relaxes the muscle; in mast cells it reduces the release of inflammatory mediators (Ventolin HFA label).

Skeletal muscle also carries beta-2 receptors. This is why albuterol causes tremor and why, at high doses, it can shift potassium into cells and influence muscle protein turnover (see below).

Albuterol vs clenbuterol

Both are beta-2 agonists, and both are prohibited in sport. They differ mainly in how long they act and in their regulatory status:

Feature	Albuterol	Clenbuterol
Duration	Short-acting; half-life about 5 h	Long-acting (see the clenbuterol page)
US approval for humans	Yes: inhalers, nebulizer solution, tablets	No; veterinary (horse) product only
WADA class	S3 beta-2 agonists, with an inhaled-dose exception	S1 anabolic agents, no exception

Pharmacokinetics

Very little albuterol reaches the bloodstream after a normal inhaled dose. The oral route gives much higher blood levels. From the US labels:

Parameter	4 mg oral tablet	Inhaled (Ventolin HFA, 1,080 µg test dose)
Peak plasma level	About 18 ng/mL	About 3 ng/mL
Time to peak	Within 2 h	0.42 h
Elimination half-life	About 5 h	About 4.6 h
Onset of airway effect	Within 30 min	Mean 5.4 min to a 15% FEV₁ rise
Peak airway effect	2–3 h	Mean 56 min
Duration of effect	Up to 8 h or longer	About 4 h (up to 6 h in some)

Note that the inhaled figures come from a test dose of 1,080 µg, twelve times a single 90 µg puff. The label states that systemic levels are low at recommended inhaled doses.

After an 8 mg oral dose of radiolabeled albuterol, 76% was recovered in urine over 3 days, mostly in the first 24 hours, and 60% of that was a metabolite. About 4% appeared in feces.

Approved medical use

US labels approve albuterol for the following:

relief or prevention of bronchospasm in reversible obstructive airway disease (asthma and similar conditions);
prevention of exercise-induced bronchospasm (inhaled forms).

Product	Population	Labeled dose
Inhaler (90 µg per puff)	Age 4 and older	2 puffs every 4–6 h; 1 puff every 4 h may be enough for some
Inhaler, exercise-induced bronchospasm	Age 4 and older	2 puffs 15–30 min before exercise
Tablets	Adults and children 12 and older	2 or 4 mg three or four times a day; maximum 8 mg four times a day; total not over 32 mg/day
Tablets	Children 6–12	2 mg three or four times a day; not over 24 mg/day
Tablets	Elderly or beta-agonist-sensitive patients	Start at 2 mg three or four times a day

The Ventolin HFA label states that more frequent use or a greater number of puffs is not recommended. Needing more doses than usual can signal that asthma is getting worse and needs reassessment, often with an anti-inflammatory drug such as an inhaled corticosteroid.

Albuterol is also used in hospitals to lower dangerously high blood potassium. An ILCOR meta-analysis found that inhaled or intravenous salbutamol, insulin with glucose, or a combination lowered potassium by an average of 0.7–1.2 mmol/L in adults, with very low to low certainty of evidence (Jessen et al., Resuscitation 2025). This is the same potassium shift that makes hypokalemia a side effect.

What the research shows

Beta-2 agonists raise muscle mass strongly in livestock and rodents, at doses far above human ones. Human data on albuterol are limited to a handful of small trials, mostly at oral doses of 16 mg/day.

Muscle mass and strength in healthy men

Study	Design, n	Albuterol dose and duration	Main result vs placebo
Martineau et al., Clin Sci 1992	Placebo-controlled, 12 healthy men, no training	Slow-release oral, 3 weeks	Quadriceps strength +12% at 14 days; no change in lean body mass or limb size
Caruso et al., MSSE 1995	22 men (13 albuterol, 9 placebo), 9 weeks of knee-extension training	16 mg/day for 6 weeks	Some strength and power measures improved more with albuterol
Hostrup et al., J Physiol 2018	Crossover, 12 trained men, single leg workout	Oral, 6 × 4 mg, with a 4-day lead-in treatment period	Myofibrillar protein synthesis 0.079 vs 0.066 %/h; protein breakdown also higher
Jessen et al., J Appl Physiol 2021; Hostrup et al., Scand J Med Sci Sports 2026	Double-blind RCT, 30 trained men randomized, 26 completed; supervised resistance training 3×/week	16 mg/day for 11 weeks	Lean mass +1.8 kg more than placebo (95% CI 0.5–3.1); no change in fat mass

The 11-week trial is the largest and most informative. It is reported in two papers. Within groups, lean mass rose 4.5 kg with albuterol and 2.6 kg with placebo. Other results:

Fiber growth: cross-sectional area of fast-twitch type IIa fibers rose 35% with albuterol vs 21% with placebo.
Strength: quadriceps peak torque rose about 13% in both groups, so the extra muscle did not translate into extra strength.
Sprint: mean power in a 10-second cycling sprint rose 12% vs 7%; peak power did not differ.
Fat: body mass rose in line with lean mass, and the investigators observed no apparent change in fat mass in either group.

Fat loss

Albuterol raises energy use at rest. In 12 healthy young men, a 24 mg oral dose roughly doubled leg oxygen consumption before exercise, and raised leg glucose uptake and oxygen use in recovery (Onslev et al., JCEM 2022).

That does not show fat loss. In the only long-term controlled trial in healthy men (11 weeks, 16 mg/day), fat mass did not change measurably (Hostrup et al., 2026). We found no controlled human trial showing that albuterol reduces body fat.

About “a safer clenbuterol for cutting.” Albuterol is often presented as a mild fat burner. The controlled human evidence shows lean-mass gains during training but no measurable fat loss, alongside reduced aerobic fitness gains and echocardiographic changes in the heart wall.

Athletic performance

A meta-analysis of 34 studies in people without asthma pooled 44 placebo-controlled comparisons of beta-2 agonists on efforts lasting 1 minute or less (Riiser et al., BJSM 2020):

Subgroup	Standardized effect (95% CI)
All beta-2 agonists	0.29 (0.16–0.42), about 5% better performance
Oral	0.51 (0.25–0.77)
Inhaled	0.16 (0.02–0.30)
Doses within WADA limits	0.14 (0.00–0.28)
Several weeks of treatment	0.50 (0.20–0.80)

In plain terms, oral and multi-week use improved strength and sprint performance, while it is uncertain whether WADA-permitted inhaled doses do. A companion meta-analysis of 47 studies found no effect on aerobic (endurance) performance: standardized difference 0.051 (95% CI −0.020 to 0.122), regardless of drug, dose, route or duration (Riiser et al., BJSM 2021).

Muscle disease (FSHD)

Albuterol was tested as a treatment for facioscapulohumeral muscular dystrophy (FSHD), an inherited muscle-wasting disease:

Pilot (open label): 15 patients on sustained-release albuterol 16 mg/day for 3 months gained 1.29 kg of lean mass (Kissel et al., Neurology 1998).
Randomized trial: 90 patients received placebo or sustained-release albuterol 8 mg or 16 mg twice daily for 1 year (Kissel et al., Neurology 2001). Global strength did not improve. The high dose added lean mass (+1.57 kg vs +0.25 kg on placebo), and grip strength improved in both albuterol arms.
Training trial: in 65 patients, albuterol improved some isometric strength measures and muscle volume, but the authors described the benefit as limited (van der Kooi et al., Neurology 2004).

A Cochrane review concluded that randomized trials did not support any drug treatment for FSHD (Rose and Tawil, Cochrane 2004). Albuterol is not approved for any muscle disease.

Side effects and risks

Common effects

The tablet label lists these as the most frequent adverse reactions in clinical trials:

Reaction	Incidence
Nervousness	20%
Tremor	20%
Headache	7%
Tachycardia (fast heart rate)	5%
Palpitations	5%
Muscle cramps	3%
Sleeplessness, weakness, dizziness, nausea	2% each

Side effects are much less frequent with normal inhaled doses. In the Ventolin HFA trials, the most common reactions (3% or more) were throat irritation, respiratory infections, cough and musculoskeletal pain. In the 11-week trial of 16 mg/day oral albuterol, 5 participants in the albuterol group reported tremor or palpitations, all mild and transient (Hostrup et al., 2026).

Heart and circulation

The labels warn that albuterol can raise pulse rate and blood pressure and can cause ECG changes, such as T-wave flattening, QTc prolongation and ST depression. Caution is advised in people with the following:

coronary artery disease;
heart rhythm disorders;
high blood pressure.

The Ventolin HFA label also notes that deaths have been reported with excessive use of inhaled sympathomimetics in asthma. The tablet label states that cardiac arrest and death may be associated with abuse of albuterol tablets. Overdose can cause heart rates up to 200 beats per minute, arrhythmias, seizures and hypokalemia.

In the 11-week training trial, cardiac MRI showed no between-group difference in heart structure or left ventricular mass. Echocardiography, however, showed greater posterior, septal and relative wall thickness with albuterol. The same trial found the following:

treadmill time to exhaustion rose 7% with placebo but did not improve with albuterol;
muscle capillary density and the activity of two oxidative enzymes (citrate synthase and HADH) fell with albuterol only.

The long-term meaning of these changes is unknown, and the trial was not designed to detect clinical events.

Potassium and blood sugar

Beta-2 agonists can cause significant hypokalemia (low blood potassium) by shifting potassium into cells. The labels describe the drop as usually transient, but low potassium can provoke arrhythmias. Large intravenous doses have been reported to worsen pre-existing diabetes and ketoacidosis. Hyperglycemia and metabolic acidosis appear among overdose signs.

Paradoxical bronchospasm and allergy

Inhaled and oral albuterol can rarely cause paradoxical bronchospasm, a sudden worsening of airway narrowing that may be life-threatening. With inhalers, it often happens with the first use of a new canister. Hypersensitivity reactions include hives, angioedema, rash and anaphylaxis.

Interactions

The labels flag these combinations:

Drug	Concern
Beta-blockers	Block albuterol’s effect and may cause severe bronchospasm in people with asthma
Non-potassium-sparing diuretics (loop, thiazide)	ECG changes and hypokalemia can be worsened
MAO inhibitors or tricyclic antidepressants (or within 2 weeks of stopping)	Effects on the vascular system may be potentiated
Other oral sympathomimetics	Combined use not recommended because of cardiovascular effects
Digoxin	Albuterol lowered digoxin levels by 16–22% in volunteers

Pregnancy and animal findings

There are no adequate controlled studies in pregnant women. The following findings come from animals and have not been shown in people:

in mice, injected albuterol caused cleft palate in 4.5–9.3% of fetuses at the two higher doses tested;
in rabbits, a very high oral dose caused skull defects (cranioschisis);
in rats, two years of dietary albuterol caused benign smooth-muscle tumors of the mesovarium, an effect blocked by propranolol.

Legal status and use outside medicine

In the US, albuterol is a prescription (Rx-only) drug. It is not among the substances listed in Schedule III (21 CFR 1308.13).

The WADA 2026 Prohibited List bans all beta-2 agonists, in and out of competition, as “Specified Substances” (WADA 2026 Prohibited List). Its exceptions and limits for salbutamol are:

inhaled salbutamol is permitted up to 1,600 µg over 24 hours, in divided doses not exceeding 600 µg over any 8 hours;
the exception covers inhalation only, so oral tablets fall under the general ban;
a urine level above 1,000 ng/mL is treated as an adverse analytical finding unless a controlled pharmacokinetic study shows it resulted from a permitted inhaled dose;
salbutamol at any level found together with a diuretic or masking agent is an adverse finding unless the athlete holds a therapeutic use exemption for both.

For scale, 1,600 µg is about 18 puffs of a 90 µg inhaler. A review by the group behind the 2018–2026 trials notes that inhalation at high doses can also have anabolic and fat-burning actions, and that such doses would usually be caught by doping control (Hostrup et al., Drug Test Anal 2020).

Albuterol also appears in surveys of people who use anabolic steroids. A survey at four San Francisco gyms included 40 steroid users and 179 non-users; steroid users reported using more performance-enhancing drugs overall (8.7 vs 3.7) (Ip et al., Res Social Adm Pharm 2019). Summarizing that survey, Hostrup and colleagues report that 10% of the steroid users also used salbutamol (Hostrup et al., 2026). In the European pharmacovigilance database, 1,310 of 62,879 salbutamol adverse-reaction reports (2.08%) involved misuse, abuse, overdose, dependence or off-label use (Milano et al., Basic Clin Pharmacol Toxicol 2018).

Key takeaways

An asthma drug, not a steroid. Albuterol (salbutamol) is a short-acting beta-2 agonist approved to treat and prevent bronchospasm, with a half-life of about 5 hours.
High oral doses add some lean mass. In an 11-week trial, 16 mg/day oral albuterol added 1.8 kg more lean mass than placebo during resistance training, without extra strength.
No demonstrated fat loss. It raises energy use acutely, but fat mass did not change in the controlled training trial.
Trade-offs in the heart and fitness. The same trial found thicker heart walls on echocardiography, lower muscle oxidative capacity and no endurance improvement.
Common side effects are sympathomimetic. Tremor and nervousness affected about 20% of tablet users in trials; low potassium, fast heart rate and ECG changes are labeled risks.
Restricted in sport. WADA bans it except for inhaled use up to 1,600 µg per day, with a 1,000 ng/mL urine threshold.

Sources

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Jessen S, Reitelseder S, Kalsen A, et al. β2-Adrenergic agonist salbutamol augments hypertrophy in MHCIIa fibers and sprint mean power output but not muscle force during 11 weeks of resistance training in young men. J Appl Physiol. 2021;130(3):617–626. PubMed.
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Code of Federal Regulations. 21 CFR 1308.13, Schedule III. 21 CFR 1308.13.

Albuterol