In its capacity as a short acting beta 2 agonist salbutamol can be delivered to its site of action in a variety of ways:
Metered Does Inhalers: These are the commonest method of delivery of salbutamol as they are small and convenient to carry and deliver a meter does of the drug directly to the lungs.
Nebulisers: Another common form of delivering the drug this also delivers the drug straight to the lungs however over a longer period of time. The inhaled forms of salbutamol have a faster onset of action, fewer side effects, and are more effective than the syrup or tablet forms.
Solution (Injections + syrups): Salbutamol can be injected (intravenous, subcutaneous or intramuscular) to treat very severe asthma or the solution can be inhaled. Each millilitre of Ventolin inhalation solution contains 5 mg of salbutamol (as 6 mg of salbutamol sulphate) in an aqueous solution containing benzalkonium chloride. Sulphuric acid is used to adjust the pH to between 3 and 5. Ventolin inhalation solution contains no sulphating agents. Ventolin inhalation solution is a clear, colourless to light yellow solution.
Ventolin syrup contains 2 mg of salbutamol as 2.4 mg of salbutamol sulphate in each 5 ml.
Tablets + extended release tablets: Each Ventolin tablet contains 2 or 4 mg of salbutamol as 2.4 or 4.8 mg, respectively, of salbutamol sulphate. Each Proventil Repetab extended-release tablet contains a total of 4 mg (2 mg in the coating for immediate release and 2 mg in the core for release after several hours) of salbutamol as 4.8 mg of salbutamol sulphate. The inactive ingredients for salbutamol extended-release tablets include: butylparaben, calcium phosphate, calcium sulphate, lactose, magnesium stearate, oleic acid and titanium dioxide.
The slower acting extended release tablets have a duration of action of at least 12 hours after a single dose. It can be used with anti-inflammatory drugs for long term control of symptoms, especially night coughs and to prevent exercise induced asthma.
Salbutamol can be delivered in several different forms:
Salbutamol is still commonly delivered as a racemic mixture (+,-) salbutamol, even though S-Salbutamol is know to have a detrimental effect on asthma suffers (in fact the exact opposite effect of the R Isomer, see Bioactivity). Although the racemic mixture does have, overall, a beneficial effect the R isomer alone is much more effective is asthma treatment.
- Salbutamol sulphate: molecular weight of 576.7, empirical formula (C13H21NO3)2·H2SO4, a white crystalline powder, soluble in water and slightly soluble in ethanol.
- Salbutamol hydrochloride
The side effects of salbutamol generally result from the drugs action on muscles such as cramps or tremors. Other side effects come from the drugs action on beta 1 adrenoceptors in cardiac muscle (500 time less binding than beta 2) generally causing vasodillation with resulting effect on blood pressure and the heart.
More common side effects include: Aggression, agitation, cough, diarrhoea, dizziness, excitement, general bodily discomfort, headache, heartburn, increased appetite, increased blood pressure, indigestion, irritability, laboured breathing, light-headedness, muscle cramps, nausea, nervousness, nightmares, nosebleed, over activity, palpitations, rapid heartbeat, rash, ringing in the ears, shakiness, sleeplessness, stomach ache, stuffy nose, throat irritation, tooth discoloration, tremors, vomiting, wheezing, worsening bronchospasm.
Less common side effects include: Chest pain or discomfort, difficulty urinating, drowsiness, dry mouth and throat, flushing, high blood pressure, muscle spasm, restlessness, sweating, unusual taste, vertigo, weakness.
Rare side effects following the use of inhaled salbutamol include: Hoarseness, skin rash or hives, hypokalemia, myocardial insufficiency, heart failure, angina-pectoris, hypertension, severe cardiovascular disease, diabetes-mellitus, maternal-thyrotoxicosis.
Salbutamols only other documented use is in obstetrics in uncomplicated premature labor.