In vitro and in vivo performance modelling and optimisation of different dry powder inhalers: A complementary study of neural networks, genetic algorithms and decision trees.

INTRODUCTION: Aerosol delivery from DPIs could be affected by different factors. This study aimed to evaluate and predict the effects of different factors on drug delivery from DPIs. METHODS: Modelling and optimisation for both in vitro and in vivo data of different DPIs (Diskus, Turbohaler and Aerolizer) were carried out using neural networks associated with genetic algorithms and the results are confirmed using a decision tree (DT) and random forest regressor (RFR). All variables (the type of DPI, inhalation flow, inhalation volume, number of inhalations and type of subject) were coded as numbers before using them in the modelling study. RESULTS: The analysis of the in vitro model showed that Turbohaler had the highest emitted dose compared with the Diskus and the Aerolizer. Increasing flow resulted in a gradual increase in the emitted dose. Little differences between the inhalation volumes 2 and 4 litres were shown at fast inhalation flow, and interestingly two inhalations showed somewhat higher emitted doses than one-inhalation mode with Turbohaler and Diskus at slow inhalation flow. Regarding the in vivo model, the percent of drug delivered to the lung was highly increased with Turbohaler and Diskus in healthy subjects where continuous contour lines were observed. The Turbohaler showed increased lung bioavailability with the two-inhalation modes, the Diskus showed a nearly constant level at both one and two inhalations at slow inhalation. The Turbohaler and Aerolizer showed little increasing effect moving from one to two inhalations at slow inhalation. CONCLUSIONS: Modelling of the input data showed a good differentiating and prediction power for both in vitro and in vivo models. The results of the modelling refer to the high efficacy of Diskus followed by Turbohaler for delivering aerosol. With two inhalations, the three DPIs showed an increase in the percent of drug excreted at slow inhalations.

Effect of Oxygen Flow on Aerosol Delivery From a Nebulizer With a Holding Chamber.

BACKGROUND: A new holding chamber was designed to be used with a vibrating mesh nebulizer to increase the total inhalable dose for patients. It facilitates intermittent and continuous nebulization as well as the optional supply of supplemental oxygen via a T-piece with a mouthpiece adapter. This study aimed to evaluate the effect of oxygen introduction in the new holding chamber on aerosol delivery using a vibrating mesh nebulizer. METHODS: The study was divided into 2 parts. First, the total inhalable dose of 1 mL of a respirable solution (nominal dose of 5,000 µg-salbutamol) was determined using a breathing simulator set to provide a tidal volume of 500 mL, a breathing frequency of 15 breaths/min, and an inspiratory:expiratory ratio of 1:1 for adults as a quiet-breathing pattern. Three experimental nebulizer setups were used: a vibrating mesh nebulizer with the holding chamber and oxygen set at 6 L/min, a vibrating mesh nebulizer with the holding chamber and no oxygen, and a vibrating mesh nebulizer with the T-piece. Aerodynamic particle size characterizations were determined using cooled Andersen cascade impaction at an inhalation flow of 15 L/min. Second, we performed an in vivo study involving 12 healthy non-smoking subjects (6 female) who were > 18 y old with an average FEV1 > 90% of predicted. Using normal tidal breathing, subjects inhaled 1 mL of nebulized salbutamol (5,000 µg) through the vibrating mesh nebulizer with the holding chamber with and without oxygen and through the vibrating mesh nebulizer with a T-piece. To analyze salbutamol content, urine samples were obtained 30 min after dosing as an index of lung deposition, and their urine was cumulatively collected for 24 h as an index of systemic absorption. RESULTS: The holding chamber significantly increased the total inhalable dose or amount of salbutamol excreted in the first 30 min, as well as the amount of salbutamol excreted over a 24-h period compared to the dose received with the vibrating mesh nebulizer with a T-piece (P = .005, P = .034, and P = .02, respectively), and relatively decreased the mass median aerodynamic diameter, although the difference was not significant. However, when oxygen was introduced in the holding chamber, the total inhalable dose, or amount of salbutamol excreted in the first 30 min, significantly decreased compared to use without oxygen (P = .003, P = .03 respectively). No significant difference was found between the vibrating mesh nebulizer with the holding chamber with oxygen and the vibrating mesh nebulizer with a T-piece. CONCLUSIONS: The vibrating mesh nebulizer with a holding chamber and without oxygen resulted in much better aerosol delivery compared to vibrating mesh nebulizer with a holding chamber and with oxygen delivery and to the vibrating mesh nebulizer with a T-piece. The use of oxygen with the holding chamber significantly decreased aerosol delivery and its benefit, and recommended flow should be reevaluated.

Inhaled salbutamol from aerolizer and diskus at different inhalation flows, inhalation volume and number of inhalations in both healthy subjects and COPD patients.

The aim of the present study was to demonstrate the effect of inhalation-flow, inhalation-volume and number of inhalations on aerosol-delivery of inhaled-salbutamol from two different dry powder inhalers (DPIs) in both healthy-subjects and chronic obstructive pulmonary disease (COPD) patients. Relative pulmonary-bioavailability and systemic-bioavailability of inhaled-salbutamol, delivered by Diskus and Aerolizer, was determined in 24-COPD patients and 24-healthy subjects. The healthy-subjects and the COPD-patients participated in the study for 7 days in which they received 4 study doses of 200 µg salbutamol (one slow-inhalation, two slow-inhalations, one fast-inhalation, and two fast-inhalations) in four alternative days with 24 hr washout period after each dose. Two urine-samples were collected from each study subjects. The first was provided 30 min post inhalation (USAL0.5), as an index of relative pulmonary-bioavailability, and the second was pooled to 24 hr post inhalation (USAL24), as an index of systemic-bioavailability. Fast-inhalation resulted in significantly higher USAL0.5 and USAL24 than slow-inhalation (p˂0.05) after one-inhalation in both healthy-subjects and COPD-patients but there was no significant difference between slow and fast-inhalation after two-inhalations. One-inhalation resulted in significantly higher USAL0.5 and USAL24 in healthy-subjects compared to COPD-patient at both slow and fast-inhalation (p˂0.05) except USAL0.5 with Diskus at slow-inhalation there was no significant difference. Also, two-inhalations resulted in significantly higher USAL0.5 and USAL24 compared to one-inhalation at slow-inhalation only (p˂0.05). No significant difference was found between Aerolizer and Diskus except in USAL0.5 of one slow-inhalation in both health-subjects and COPD-patients (p = 0.048 and 0.047, respectively). Device-formula relation is present at low inhalation-flow since Diskus resulted in significantly higher USAL0.5 and USAL24 in healthy-subjects compared to COPD-patient at slow inhalation than Aerolizer. It is essential to inhale-twice and as hard and deep as possible from each dose when using DPI especially with COPD-patients having poor inspiratory efforts such as elderly patients and children.

Total emitted dose of salbutamol sulphate at different inhalation flows and inhalation volumes through different types of dry powder inhalers.

The aim of the present study was to compare the performance of two different dry powder inhalers (DPIs) at different inhalations volumes and inhalation flows. Ventolin Diskus contain blisters of 200µg salbutamol. To test the TED from Aerolizer, salbutamol in Diskus blister was emptied and placed in size 3 capsules suitable for use with Aerolizer. Total emitted dose (TED) delivered by Diskus and Aerolizer was determined using DPI sampling apparatus after one and two inhalations from the same dose. 10-60L/min inhalation flows at 2 and 4L inhalation volume were used in the determination. At inhalation flow ≤30L/min, two inhalations resulted in higher TED than one inhalation (p < 0.05) and Diskus resulted in higher TED than Aerolizer (p < 0.05). The highest TED was at inhalation flow 40L/min above which the effect of the second inhalation and formula device relation were negligible. Device formula relation is present at low inhalation flow but at flow >30L/min Diskus drug formula can be delivered by Aerolizer with no significant difference in TED produced. For the best TED patients are required to inhale as fast as possible (a minimum of 40L/min). At lower inhalation flow two inhalations results in better emitted dose than one inhalation for both DPIs. So, we recommend patients with poor inspiratory efforts to inhale twice and as hard and deep as possible from each dose as they may not receive much benefit from one inhalation even when using DPI with low resistance (Aerolizer) or medium resistance (Diskus). However, further in-vivo study are required to validate this recommendtation.

Three New Methods for Resolving Ternary Mixture with Overlapping Spectra: Comparative Study.

In this study three new spectrophotometric methods have been developed and validated for simultaneous determination of ternary mixture of metronidazole (MET), diloxanide (DLX) and mebeverine HCl (MEB) without prior separation steps. The newly introduced methods consisted of several steps utilizing either zero order or ratio spectra without the need for derivatization steps. The developed methods are called area under the curve ("AUC"), modified absorption factor (MAFM) and modified amplitude center (MACM) spectrophotometric methods. Selectivity and validity of the methods were checked by using different synthetic mixtures and by analysis of their combined dosage form where low standard deviation values and good percentage recoveries were obtained. Additionally, methods linearity, accuracy and precision were determined following United States Pharmacopoeia (USP) recommendations. The obtained results were found to agree with the reported ones when they were statistically compared using One Way ANOVA test. These methods are easily applied during drug quality control studies and in laboratories lacking the facilities of chromatographic methods of analysis. Data manipulation steps are very simple, hence these methods can be considered as time and money saving methods comparing to chromatographic methods of analysis.

Different Spectrophotometric and TLC-Densitometric Methods for Determination of Mesalazine in Presence of Its Two Toxic Impurities.

Two selective spectrophotometric and TLC-densitometric methods were developed for determination of mesalazine (ME) and its two toxic impurities, 4-amino phenol (4AP) and salicylic acid (SA) without preliminary separation. The proposed methods are: ratio difference in the subtracted spectra (RDSS) {Method 1}, area under the curve (AUC) {Method 2} and TLC-densitometric {Method 3}. In method {1} combination of measuring the amplitude of the constant at 350 nm (using standard spectrum of 10 µg/mL ME as a divisor) and ratio difference in the subtracted ratio spectrum for determination of 4AP and SA using the ratio difference at 221.4 and 242.2 nm, 230 and 241.2 nm, respectively. In method {2} ME was determined by direct measuring the AUC in the wavelength range of 350-370 nm while the impurities could be determined by dividing their spectra by standard spectrum of 10 µg/mL ME then interference from ME was eliminated by subtracting the amplitude of the constant at 350 nm then multiplying by the divisor. AUC in the range of 220-230 and 235-245 nm was used for measuring concentrations of 4AP and SA. On the other hand, the third method {3} is TLC-densitometric method at which chromatographic separation was achieved using ethyl acetate-methanol-triethylamine (8.5 : 2 : 0.7, v/v/v) as a developing system with UV scanning at 230 nm. The validation of the proposed methods was performed according to International Conference on Harmonization (ICH) guidelines. No significant difference was found when these methods were compared to the reported one.

Validated chromatographic and spectrophotometric methods for analysis of some amoebicide drugs in their combined pharmaceutical preparation.

This work is concerned with development and validation of chromatographic and spectrophotometric methods for analysis of mebeverine HCl (MEH), diloxanide furoate (DF) and metronidazole (MET) in Dimetrol® tablets - spectrophotometric and RP-HPLC methods using UV detection. The developed spectrophotometric methods depend on determination of MEH and DF in the combined dosage form using the successive derivative ratio spectra method which depends on derivatization of the obtained ratio spectra in two steps using methanol as a solvent and measuring MEH at 226.4-232.2 nm (peak to peak) and DF at 260.6-264.8 nm (peak to peak). While MET concentrations were determined using first derivative (1D) at λ = 327 nm using the same solvent. The chromatographic method depends on HPLC separation on ODS column and elution with a mobile phase consisting water: methanol: triethylamine (25: 75: 0.5, by volume, orthophosphoric acid to pH =4). Pumping the mobile phase at 0.7 ml min-1 with UV at 230 nm. Factors affecting the developed methods were studied and optimized, moreover, they have been validated as per ICH guideline and the results demonstrated that the suggested methods are reproducible, reliable and can be applied for routine use with short time of analysis. Statistical analysis of the two developed methods with each other using F and student's-t tests showed no significant difference.