Spray Angle Measurement in Pharmaceutical Sprays: Correct Methodology and Common Pitfalls

Abstract

Purpose

The primary purpose of this perspective article is to challenge the conventional approach of spray angle measurement in pharmaceutical sprays, which has long relied on the formula θ = \(\:{\text{tan}}^{-1}\frac{l}{r}\). This article introduces and justifies the use of the correct formula, θ =\(\:2{\text{tan}}^{-1}\frac{r}{l}\), which provides a more accurate method for calculating spray angles. Accurate spray angle measurement is crucial for determining drug dispersion and coverage, ensuring uniform deposition on target areas such as wounds and topical treatments,optimizing formulation and device performance. Inaccurate measurement may lead to under-dosing or over-dosing. Consistent spray patterns also guarantee reproducibility, which is essential for maintaining product quality and ensuring effective clinical outcomes.

Methods

A comprehensive review of existing literature was conducted to identify and analyse the use of the θ = \(\:{\text{tan}}^{-1}\frac{l}{r}\) formula in spray angle measurement. The mathematical and geometric principles underlying both formulas were examined and compared. Additionally, the implications of using the correct formula, θ =\(\:2{\text{tan}}^{-1}\frac{r}{l}\), were explored in the context of pharmaceutical spray performance.

Results

The analysis revealed that the traditional formula, θ = \(\:{\text{tan}}^{-1}\frac{l}{r}\), often leads to inaccuracies in determining the spray angle, which can result in suboptimal spray performance and drug delivery. The correct formula, θ =\(\:2{\text{tan}}^{-1}\frac{r}{l}\), addresses these inaccuracies, offering a more precise and reliable method for measuring spray angles ensuring accurate spray characterization.

Conclusion

This article advocates for the adoption of the θ = \(\:2{\text{tan}}^{-1}\frac{r}{l}\)formula as the standard for spray angle measurement in pharmaceutical sprays. By correcting the longstanding error in the methodology, this new approach enhances the accuracy of spray characterization, ultimately contributing to better drug delivery outcomes. Further research and validation are encouraged to solidify this method as the industry standard.