Abstract
Jet nebulizers show an unreasonable variation in drug output and nebulization rates that leads to clinical and regulatory problems. Current evaluation methods appear inadequate for the purpose. Our objective was to evaluate Technetium-99m radiometry to study nebulizer parameters and the factors influencing it quantitatively. Drug output, output rate and residual mass and the effect of excipient, temperature, surface tension, air-jet speed, and equipment brand and aging were studied. Though nebulization of radiolabeled drugs followed first-order kinetics, the rates were significantly different; the heaviest drug (Tc-99m colloid) and Tc-99m salbutamol had the least nebulization. Nebulization rate for the first minute was invariably higher than the mean rate signifying the concentration effect of the solute. Drug residue was 35-75%. Drug output of different nebulizer chamber and air compressor brands was different to the extent of 270% and 180% respectively. ‘Aging’ of fluid chamber, cold drug fluid and obstruction in air-jet resulted in significant reduction in output, while addition of 2% saline as excipient did not change the output rate. Addition of ethyl alcohol resulted in a maximum of 260% enhancement (with Tc-99m salbutamol), while further reduction in surface tension was counterproductive irrespective of the drug used. We conclude that radiometry can provide valuable parametric information on the performance of different jet nebulizers.
Highlights
Jet nebulizers show an unreasonable variation in drug output and nebulization rates that leads to clinical and regulatory problems
Aerosol output has been used as an January - February 2010 www.ijpsonline.com indirect measure of drug output using gravimetric method[22], but is highly inaccurate for jet nebulizers as it assumes static drug concentration in the fluid, which is incorrect
The air compressors have been given arbitrary code names since the present study only aims to highlight the utility of radiometry as a technique for assessing performance of jet nebulizers and not to create any commercial bias regarding different medical air compressors available in the market at this stage
Summary
Jet nebulizers show an unreasonable variation in drug output and nebulization rates that leads to clinical and regulatory problems. The methods available presently for measuring nebulised drug output appear inadequate, more so because a variety of factors are known to influence nebulization rate but the present methods are inadequate to verify and quantify their influence It is important both from medical and regulatory points of view, that performance of each nebulizer-compressor system be specified and such analysis methods should be capable of measuring the influence of various given factors on the nebulizer drug output. Such methods need to be ubiquitous, accurate and simple to perform, considering the present and future expansion of the use of inhalation route of drug delivery
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