Pharmacokinetic differences between chlorofluorocarbon and chlorofluorocarbon-free metered dose inhalers of beclomethasone dipropionate in adult asthmatics.

We have compared the serum pharmacokinetics of the metabolites of beclomethasone dipropionate after inhalation from chlorofluorocarbon (CFC) and hydrofluoroalkane HFA-134a (HFA) formulations in asthmatic patients. Twenty-three patients completed this open-label, randomized, single-dose, three-period crossover study. Each patient received in separate periods 200 microg or 400 microg HFA-beclomethasone dipropionate, or 400 microg CFC-beclomethasone dipropionate. Venous blood samples were collected over 24 h for the determination of beclomethasone esters and beclomethasone in the serum. Significant differences in pharmacokinetics following HFA- and CFC-beclomethasone dipropionate were observed. Following a 400 microg beclomethasone dipropionate dose, the HFA formulation gave mean maximum concentrations (Cmax) and area under the curve (AUC) values of beclomethasone esters of 1153 pg mL(-1) and 4328 pg h mL(-1), respectively, and beclomethasone Cmax and AUC values of 69 pg mL(-1) and 682 pg h mL(-1), respectively. These values were approximately 2-3-fold those seen with the CFC formulation (beclomethasone esters Cmax and AUC of 380 pg mL(-1) and 1764 pg h mL(-1), respectively; beclomethasone Cmax and AUC of 41 pg ml(-1) and 366 pg h mL(-1), respectively). Beclomethasone esters, the major component of beclomethasone dipropionate in the serum, peaked significantly earlier for the HFA formulation (0.8 h) than for the CFC formulation (2 h). Tests for dose proportionality of beclomethasone esters pharmacokinetics following HFA-beclomethasone dipropionate showed that the two hydrofluoroalkane strengths were proportional. The more rapid and greater efficiency of systemic drug delivery of the HFA formulation compared with the CFC formulation can be explained if most of each inhalation from CFC-beclomethasone dipropionate is swallowed and absorbed orally, whereas most of each inhalation from HFA-beclomethasone dipropionate is absorbed through the lungs. There is a need for comprehensive dose-response efficacy trials, with the use of the steep portion of the dose-response relationship, to evaluate the significance of these pharmacokinetic differences.

Beclomethasone relative availability of oral versus inhaled beclomethasone dipropionate from an HFA-134A metered dose inhaler.

3M has formulated a new chlorofluorocarbon-free (CFC-free) beclomethasone dipropionate (BDP) metered-dose inhaler (MDI) with the use of the propellant HFA-134a (HFA). Lung deposition studies demonstrated that the HFA BDP MDI delivers to the lungs approximately 56% of the BDP dose (ex-adaptor), a substantially higher percentage than the 5-30% delivered by conventional CFC BDP MDIs. As new sensitive bioanalytical methods are becoming available to quantitate systemic levels of inhaled corticosteroids, pharmacokinetic evaluations are emerging as sensitive and reproducible methods that can be used as a complement to the data obtained from lung deposition studies to assess and compare the performance of MDIs. The present study was designed to determine the beclomethasone (BOH) availability of oral BDP relative to inhaled HFA BDP as a first step to alloy MDI product comparisons in the future. Forty mild asthmatic patients completed this open-label, randomized, single-dose, two-period crossover study. Each patient received an oral dose of BDP (0.2, 0.5, 1, 2 or 5 mg) in one period and an inhaled dose of BDP (0.2 or 0.8 mg) in the other period, with four patients allocated to each of ten different treatment sequences. The BOH availability of orally administered BDP was approximately 40% relative to inhaled HFA BDP. In addition, the fraction of an oral dose that reaches the systemic circulation was estimated from the 40% relative availability and previous lung deposition data to be 0.26. These estimated pharmacokinetic parameters will be used in the future to further characterize the pharmacokinetics of inhaled BDP and to compare the performance of different MDI products.

Cumulative dose-response study of non-CFC propellant HFA 134a salbutamol sulfate metered-dose inhaler in patients with asthma.

STUDY OBJECTIVE: This study compares the safety and efficacy of HFA 134a salbutamol sulfate (Airomir in the 3M CFC-free system [3M Pharmaceuticals]) and CFC 11/12 salbutamol (Ventolin [Allen & Hanburys]) in a cumulative dose-response (1, 1, 2, 4, 8 inhalations at 30-min intervals) study in asthmatic patients. DESIGN: Randomized, single-blind, two-period cross-over study. PARTICIPANTS: Twenty-four stable mild to moderate asthmatics. MEASUREMENTS AND RESULTS: At all cumulative inhalations, the changes in FEV1 (absolute, percent, and percent predicted) and FVC were equivalent. There was also no significant difference in heart rate, serum potassium level, BP, 12-lead ECG, Holter monitor recordings, or adverse events. Both HFA 134a salbutamol sulfate and CFC 11/12 salbutamol displayed a significant dose-response for FEV1, FEF25-75%, FVC, serum potassium, heart rate, and systolic BP. CONCLUSIONS: HFA 134a salbutamol sulfate and CFC 11/12 salbutamol produced clinically and statistically similar airway responses and side effects. These results indicate that HFA 134a salbutamol sulfate would be a safe and effective substitute for CFC 11/12 salbutamol.

"Silent" nucleotide substitution in codon 24 of a beta+ thalassemia globin gene activates splice site in coding sequence RNA.

A beta+-thalassemia globin gene was isolated from the genome of a black patient by molecular cloning. DNA sequence analysis revealed only a single difference between this gene and the normal human beta-globin gene--adenine is substituted for thymine in the third position of codon 24. This mutation is silent at the protein sequence level. We compared the function of this beta+-thalassemia gene with the normal human beta-globin gene in monkey kidney cells using plasmid expression vectors. The codon 24 substitution activates a 5' splice site that involves the guanine-thymine dinucleotide present in codon 25, 16 nucleotides upstream from the normal exon 1-intron I boundary. Splices at the abnormal 5' site in the coding sequence are completed with the normal 3' splice site at the end of intron I. This splicing abnormality leads to a fourfold decrease in the accumulation of normally processed beta-globin mRNA, thereby causing the beta+-thalassemia phenotype.