The metabolic actions of intravenous salbutamol and aminophylline singly and in combination

Salbutamol in the Management of Asthma: A Review

Asthma is a common inflammatory disease of the lungs. The prevalence of asthma is increasing worldwide, and the tendency indicates that the number of asthma sufferers will soar in the coming years for several reasons, in particular, the lifestyles we have adopted that expose us to risk factors. Salbutamol is the first selective short-acting β2-agonist (SABA) used as an alternative reliever in the treatment of asthma. Its therapeutic effect is based on its potent smooth muscle relaxant properties, which allow the inhibition of bronchial smooth muscle contraction and subsequent bronchodilation. Salbutamol can be administered orally, intravenously (IV), intramuscularly (IM), subcutaneously, or by inhalation. For this reason, the pharmacokinetic (PK) parameters-absorption, distribution, metabolism, and elimination-are highly diverse and, consequently, the efficacy and adverse effects also differ between each formulation. Here, we review the pharmacological profile of different salbutamol formulations, focusing on their efficacy and adverse effects for its original application, asthma.

Do medicines commonly used by older adults impact their nutrient status?

Background

Chronic health conditions and polypharmacy are common among the older population and associated with increased risks of adverse events, medicine-interactions, geriatric syndromes, falls and mortality. Poor nutrition is also common in older people. Causal associations between medication use and older people's nutrient status is seldom discussed.

Objectives

The objectives of this review were to summarise the literature reporting associations between medicines commonly prescribed to older adults and nutrient deficiencies, and to discuss the clinical implications and management.

Methods

Medicine information resources (n = 5) were searched for information about nutrient deficiencies associated with common medicines used by older people and listed within the top 50 medicines prescribed by volume on the Australian Pharmaceutical Benefits Scheme. This was followed by a search for clinical studies published on PubMed from inception to April 2020. Data was extracted, tabulated and summarised with clinical information relevant to pharmacists and clinicians involved in the care of older people taking medicines.

Results

A total of 23 clinical studies were identified reporting medicine-induced nutrient deficiencies in older adults. Vitamin B12, sodium, magnesium were identified as the 3 main nutrients susceptible to deficiency by medicines used to treat cardiovascular disease, neurological conditions, gastrointestinal conditions, and diabetes. The coenzyme CoQ10 was depleted by statins.

Conclusion: Certain medicines commonly prescribed to older adults are associated with nutrient deficiencies that may be clinically significant. Given the high prevalence of comorbidities and polypharmacy it is possible that some of these individual drug-induced nutrient deficiencies are compounded, warranting both clinical and research attention.

Serum potassium responses to nebulized salbutamol administered during an acute asthmatic attack

A prospective study of 20 patients presenting to an accident and emergency department with an exacerbation of pre-existing reversible airways disease was undertaken in order to determine whether such patients incurred any changes in their serum potassium following administration of 5 mg of nebulized salbutamol. Electrolytes were estimated before and 30 min after administration of nebulized salbutamol. No other drug was administered during this period. Results indicate that nebulized salbutamol can cause a significant hypokalaemic response in such situations. Eight out of the 20 patients studied demonstrated falls in serum potassium of more than 0.3 mmol/l. Most of the falls in serum potassium occurred in patients with low pre-treatment PCO2 values; a group of patients with less severe respiratory distress. This preliminary study indicates that a further study aimed at elucidating the clinical significance of nebulized salbutamol-induced hypokalaemia is required.

Albuterol: an adrenergic agent for use in the treatment of asthma pharmacology, pharmacokinetics and clinical use

Albuterol is a long-acting beta 2-adrenergic receptor-selective drug that relaxes airway smooth muscle. It is currently available in the United States in oral and metered-dose inhaler forms. Nebulizer solutions and parenteral preparations are likely to be marketed here in the future. The chemical modifications that make albuterol beta 2-selective also promote oral bioavailability and increased duration of action by decreasing sensitivity to degradative enzymes. Albuterol can also produce undesirable dose-related effects: metabolic effects including decreased levels of plasma potassium, phosphate, calcium and magnesium; increased levels of plasma glucose, insulin, renin, lactate and ketones; peripheral vasodilation and perhaps some direct cardiac stimulation resulting in decreased systemic and pulmonary vascular resistance, increased pulse pressure and tachycardia; and skeletal muscle tremor. These side effects are most common with parenteral administration and much less prominent with aerosol administration, which yields lower systemic concentrations. Limited pharmacokinetic data suggest a long distribution phase, a terminal half-life of 3-8 hours, and 10-20% oral bioavailability. Aerosolization of albuterol or a similar agent with a compressed-air nebulizer appears to be best first-line management of the patient with acute dyspneic asthma, but appropriate preparations for this kind of therapy are currently missing from the United States market. Intravenous albuterol has also been employed in acutely dyspneic patients, but produces more side effects than carefully administered intravenous theophylline, is impaired by lack of sufficient pharmacokinetic information to guide dosing, and is of uncertain efficacy in the asthmatic with respiratory failure. However, it appears to lack the potentially life-threatening side effects that can result when theophylline is used carelessly . In the ambulatory patient, aerosolized albuterol (or a similar agent) administered by metered-dose inhaler is an excellent agent for treatment as needed and/or for prevention of acute bronchospasm triggered by exercise or other predictable cause. Advantages include a high degree of efficacy, rapid onset and long duration of effect, and minimal side effects. Regularly scheduled administration of albuterol by metered-dose inhaler is a widely used and effective maintenance medication for patients requiring long-term prophylactic therapy. However comparisons of the ability of this regimen and the other common maintenance regimens (cromolyn and theophylline) to control chronic symptoms of asthma are needed.