Long-acting beta 2-adrenoceptor agonists: a new perspective in the treatment of asthma.

New long-acting beta 2-adrenoceptor agonists, formoterol and salmeterol, may soon appear in several European countries for treatment of asthma. This review examines currently available information and compares the basic pharmacology and describes the clinical effects of these new drugs. The long duration of bronchodilation seen in clinical studies seems to be similar, whereas in isolated tissues there might be a difference in the binding characteristics to the beta 2-adrenoceptor. Long-acting beta 2-agonists could have an inhibitory effect on inflammatory events related to asthma, but the clinical relevance of these effects is not clear at present. Long-term studies up to one year with both new drugs have not shown any unexpected side-effects, and no tachyphylaxis to beta-adrenoceptor stimulation has been reported. Patients appear to strongly prefer the new drugs compared to the short-acting beta 2-agonists. The potential place for these drugs in the treatment of asthma is discussed and some pitfalls pointed out. It is likely that the long-acting beta 2-agonists will be beneficial to many asthmatic patients.     

Salmeterol, formoterol, and salbutamol in the isolated guinea pig trachea: differences in maximum relaxant effect and potency but not in functional antagonism.

BACKGROUND--Formoterol and salmeterol are new long acting beta 2 adrenoceptor agonists. The maximum relaxant effect, potency and functional antagonism against carbachol induced contraction for salmeterol, formoterol and salbutamol have been compared in the guinea pig isolated trachea. In addition, the possibility of inducing a non-beta adrenoceptor mediated relaxation by salmeterol was studied. METHODS--Concentration response experiments were conducted with isolated tracheal preparations (n = 4-6 in all experiments), precontracted by carbachol to cause either 40% (60 nmol/l), 80% (0.3 mumol/l) or 100% (3 mumol/l, supramaximal) of the maximum contraction. Each beta agonist was added cumulatively at each level of precontraction. Additional cumulative concentration response experiments were conducted for salmeterol alone at the highest level of precontraction, with and without beta blockade by sotalol (1 mmol/l). With the drug concentrations which produced the maximum response and the highest level of precontraction, the relaxation of formoterol (10 nmol/l) and salmeterol (1 mumol/l) was also compared non-cumulatively. Finally, with the corresponding drug concentrations and precontraction, the relaxant effect was compared for formoterol (10 nmol/l) in salmeterol relaxed airways with that of salmeterol (1 mumol/l) in formoterol relaxed airways. RESULTS--The increase in carbachol concentration from 60 nmol/l to 3 mumol/l induced a rightward shift in the mean (SE) concentration (log steps) causing 50% maximum relaxation for salmeterol (0.73 (0.17)), formoterol (0.85 (0.18)), and salbutamol (1.13 (0.11)). Significant differences in the maximum relaxant effect were shown at the highest level of precontraction only, with a remaining active tension of percentage precontraction of 27% (4%) for 1 mumol/l salbutamol and 35% (3%) for 10 nmol/l formoterol compared with 50% (2%) for 1 mumol/l salmeterol. The rank order of potency was: formoterol > salbutamol approximately salmeterol at all levels of precontraction (-log EC50: 9.32 (0.05) for formoterol, 7.82 (0.08) for salbutamol, and 7.50 (0.13) for salmeterol at 80% maximum precontraction). Beta blockade by sotalol (1 mmol/l) significantly inhibited the relaxation induced by salmeterol (1 mumol/l) (remaining active tension: 104% (1%) v 71% (11%) of precontraction) but not the relaxation induced by salmeterol (10 mumol/l) (remaining active tension: 75% (5%) v 71% (12%) of precontraction). In the non-cumulative experiments, formoterol displayed more relaxant effect than salmeterol (remaining active tension: 51% (6%) v 65% (6%) of precontraction). Finally, formoterol significantly relaxed salmeterol relaxed airways (relaxant effect: 22% (8%) of precontraction) whereas there was no significant response to salmeterol in formoterol relaxed airways (relaxant effect: 5% (12%) of precontraction). CONCLUSIONS--In the guinea pig isolated trachea, formoterol and salbutamol produce more relaxant effect than salmeterol, suggesting that salmeterol is a partial beta 2 agonist. Very high concentrations of salmeterol may induce non-beta adrenoceptor mediated relaxation. Formoterol is more potent than both salbutamol and salmeterol. There is no pronounced difference in the magnitude of antagonism against carbachol induced contractions between salmeterol, formoterol, and salbutamol.     

Detection of Pneumocystis carinii DNA in sputum and bronchoalveolar lavage samples by polymerase chain reaction.

A polymerase chain reaction (PCR)-based assay was developed for the detection of Pneumocystis carinii DNA in induced sputum and bronchoscopic alveolar lavage samples. The primer pair was selected from the published sequence of the thymidylate synthase gene of P. carinii derived from infected rats. The amplified DNA fragment of 403 bp was detected by agarose gel electrophoresis and by Southern and slot blot hybridization. No positive reaction was seen with DNA from different microorganisms typically found in the respiratory tract. P. carinii DNA was demonstrated in 30 of 42 sputum samples from immunosuppressed patients, whereas 21 of 42 sputum samples were positive by indirect immunofluorescence (IFL). Among the 42 patients, 14 were receiving prophylactic chemotherapy. In that group, PCR detected P. carinii in nine sputum samples, whereas IFL detected P. carinii in only four sputum samples. A positive PCR result was also seen in 5 of 43 IFL-negative bronchoscopic alveolar lavage samples from patients with respiratory symptoms. The PCR assay detected 10 copies of the target DNA, which corresponds to 10(-18) g of the specific P. carinii sequence. The results indicate that PCR amplification in combination with DNA hybridization is specific and is a more sensitive diagnostic method than IFL for the detection of P. carinii.     

Tetrodotoxin does not block the epithelium-dependent release of prostaglandin E2 induced by electrical field stimulation in isolated ferret trachea

Electrical field stimulation (EFS) has previously been shown to induce the release of prostaglandin (PG) E2 from ferret tracheal epithelium. We have now conducted a study to see whether this effect of EFS is due to the activation of nerves or whether it is a non-neural effect. The release of PGE2 and 6-keto-PGF1 alpha into the bath fluid was assayed in isolated ferret tracheas with (E+) or without (E-) epithelium, stimulated by either EFS or direct vagal nerve stimulation (DNS) repeatedly for 120 min. EFS-stimulated E+ preparations showed a gradual decline in the contractile responses (30 +/- 1% of baseline) and an increase in PGE2 to 296 +/- 38 pg/ml. In EFS-stimulated, epithelium-denuded (E-) preparations, the decline was significantly lower (11 +/- 5%), as well as the final concentration of PGE2 (107 +/- 21 pg/ml). In DNS-stimulated E+ preparations, the contraction decline was 8 +/- 1% and the final concentration of PGE2 was less than 6 pg/ml. Although tetrodotoxin (TTX) abolished the contractile response in EFS-stimulated E+ preparations, it did not significantly reduce the release of PGE2 (260 +/- 6 pg/ml), whereas atropine partly counteracted the release. The bath concentration of 6-keto-PGF1 alpha increased, independently of the electrical stimulation, contractile response, or presence of the epithelium. We conclude that EFS activates the epithelium-dependent release of PGE2 by a TTX-resistant mechanism. This may be due to an activation of TTX-resistant nerves, or possibly to a non-neural effect, such as a direct effect on the epithelial cells. The results indicate that the airway epithelium has the ability to respond to certain stimuli with a pronounced release of PGE2, thereby counteracting bronchoconstriction.     

An outbreak of aseptic meningitis with a rubella-like rash probably caused by ECHO virus type 4

Summary An outbreak of aseptic meningitis in association with ECHO virus type 4 is described. This virus was isolated in 8 out of 12 cases with this syndrome from stool specimens and in two cases also from spinal fluids and furthermore from healthy family contacts. Neutralizing antibodies in the patients sera could not be demonstrated with the conventional tube tests while complement fixing antibodies with increasing titer against ECHO-4 occurred. There is an extensive heterotypic complement fixing antibody response in patients sera within the ECHO virus group between this group and the Coxsackie or the poliomyelitis group as well as beetwen the Coxsackie and the poliomyelitis groups.The choice of tissue for isolation of enteroviruses is discussed. Trypsinized human embryonic kidney seems to provide a suitable medium for this group of viruses.A rubella-like exanthem was seen in about two thirds of the virus positive patients. Some cases had diphasic course.     

COPD exacerbations: the importance of a standard definition

Efforts to assess the efficacy of new therapies in the treatment of acute exacerbations of chronic obstructive pulmonary disease (COPD) have been hampered by the lack of a widely agreed and consistently used definition. A variety of definitions have been used in clinical studies, based on changes in patient symptoms or the requirement for antibiotic therapy, oral steroids or hospitalisation. To date, none of these definitions have been assessed in detail for their reliability, responsiveness and validity determined. Considerable heterogeneity in the aetiology and manifestation of COPD exacerbations makes identification and quantification of defining symptoms extremely difficult. New approaches are therefore being sought with a view to identifying a serum or tissue marker that can be used as a valuable diagnostic tool. Improvements in data recording will also contribute to the accuracy of data retrieval and assessment. If we are to progress to a level of sophistication seen in the diagnosis and management of other diseases, it is evident that considerable research efforts will be required to improve our understanding of COPD exacerbations and develop a standard definition for these events, thereby facilitating the assessment of therapeutic approaches.     

Mucosal inhibition of cholinergic contractions in ferret trachea can be transferred between organ baths

The influence of the mucosa on the contractile responses to cholinergic nerve stimulation in an in vitro nerve muscle preparation of ferret trachea was studied. Repeated contractions were induced by alternating direct vagal nerve stimulation (DNS) and electrical field stimulation (EFS). With intact mucosa there was a marked successive decrease of the contractile responses. During 60 minutes the responses decreased to 46 +/- 8% of baseline (Mean +/- SEM, n = 6), compared to 86 +/- 2% in preparations, in which the mucosa was initially removed. The mucosa dependent inhibition could be partly blocked by indomethacin (10 microM). The inhibitory effect could be transferred via the bath fluid from a donor preparation with intact mucosa to a recipient preparation with removed mucosa. Fluid transferred from a donor preparation with removed mucosa or from indomethacin treated preparations did not affect the contractile responses in the recipient preparation. We conclude that ferret tracheal mucosa can release a factor which inhibits the contractile responses to cholinergic nerve stimulation. The release of this factor can be blocked to a major part by indomethacin and the factor can be transferred from a donor to a recipient preparation.     

High-Dose Inhaled Budesonide May Substitute for Oral Therapy After an Acute Asthma Attack

Patients attending the emergency room with acute asthma, participating in a study comparing salbutamol (albuterol in the United States) via a dry powder inhaler (Turbuhaler®) with pressurized metered-dose inhaler (pMDI), were included in this 1-week follow-up study with the aim of assessing whether inhaled budesonide via Turbuhaler may be an alternative to prednisolone tablets after an acute asthma attack. Eighty-one patients with a mean age of 38 years and forced expiratory volume in 1 sec (FEV₁) of 64% predicted normal value after treatment with salbutamol were randomized in this double-blind, double-dummy, parallel-group study. The doses given were budesonide 1600 μg b.i.d. or prednisolone in daily doses from 40 mg (day 1) decreased to 5 mg (day 7). FEV₁ was recorded before and after the 7-day treatments and peak expiratory flow (PEF) morning and evening, clinical symptoms (visual analogue scale 0-100), and doses of rescue medication (terbutalineTurbuhaler 0.25 mg/dose) were recorded daily. The mean increase in FEV, from baseline to day 7 was 1 7.3% in the budesonide Turbuhaler group and 1 7.6% in the prednisolone group. Mean values of morning PEF increased from day 1 to day 7 by 67 L/min in the budesonide Turbuhaler group and by 57 L/min in the prednisolone group (not significant). There were no statistically significant differences between the groups in clinical symptoms and in the number of doses of rescue medication. Because of disease deterioration, five patients in the Turbuhaler group and three in the prednisolone group needed additional symptomatic as well as corticosteroid treatment. Inhaled budesonide in high doses may be a substitute for oral therapy as follow-up treatment after an acute asthma attack.