Introduction
Inhaled bronchodilators and inhaled corticosteroids were the mainstays in the management of obstructive pulmonary diseases. These agents were delivered through different inhaler devices as it was considered to be the best route to administer for better safety and efficacy outcomes.1,2 Unlike systemic drugs, inhaled medicines are rapidly directed towards the airways, allowing for rapid onset. Some of the commonly used delivery devices were nebulizers, pressurized metered-dose inhalers (pMDI), dry powder inhalers (DPI), or Soft Mist inhalers were the commonly used devices. pMDI was introduced in 1950 and it became very popular and widely used for inhalation therapy in patients with obstructive pulmonary diseases. The coordination between inhalation and actuation of inhaler was an important issue3. There was an ocean of studies published in the last few decades assessing the importance of optimal inhaler technique use and its significance over the control status of the disease. Appropriate use of inhaler devices is very important for both asthma and COPD management as it results in compromised therapeutic outcomes leading to inadequate control of symptoms. 4,5,6,7 Inhalation therapy using a valve holding chamber MDI has been shown to play a key role in the treatment of asthmatic patients as they encourage patients to breathe out of a drug pool. 3, 8. However, several studies concluded that a significant proportion of patients continue to use their inhaler devices incorrectly. 9,10
For many years, measurements of pulmonary lung function (PFT) have been used to compare efficacy. Besides the evaluation of variations in systemic bioavailability, the concentration of the salbutamol excreted in the urine post 30 minutes of inhalation is determined and correlated with the amount of drug delivered to the lungs.11 The assessment of the relative bioavailability of salbutamol in the lung by obtaining a sample of urine 30 minutes after inhalation is reproducible, clear, and effective. 12 The benefits of this approach compared to others are the use of a patient’s own inhaler, no need for either the ingestion of charcoal or the use of a radiolabelled inhaler marker. The 30-minute urinary salbutamol concentration method may also be used concomitantly with measurements of lung function to demonstrate the association between improved deposition and enhanced spirometry.11 Only a few studies employed 30 min salbutamol urinary excretion post inhalation pharmacokinetic method to determine lung bioavailability of inhaler drugs, compare inhaler medications and devices in healthy volunteers, and only study in asthma patients. 11-15 The aim of this paper is, therefore, to evaluate the urinary salbutamol concentration as a measure of relative bioavailability to the lung within the first 30 minutes after inhalation and correlate it with the total inhaler scores assessed through a standard questionnaire and control status of the disease.