Clinical efficacy and safety of the combination of ipratropium bromide and fenoterol inhaled via the Respimat Soft Mist inhaler for relief of airflow obstruction

Fenoterol functionally activates the β₃-adrenoceptor in human urinary bladder, comparison with rat and mouse: implications for drug discovery

Fenoterol has been reported to be a potent and selective β(2)-adrenoceptor agonist and is currently used clinically to treat asthma. Electrical field stimulation (EFS) of isolated urinary bladder mimics the voiding contraction by stimulating parasympathetic nerves, resulting in neurogenic contractions. To determine if stimulation of β(2)-adrenoceptors can inhibit this response, fenoterol was tested against EFS-induced contractions in human isolated urinary bladder and compared with mouse and rat. Bladder strips were mounted in organ baths and reproducible contractions induced by EFS. Fenoterol was added cumulatively in the presence of the β(2)-adrenoceptor antagonist ICI118551 or the β(3)-adrenoceptor antagonist L-748337. Fenoterol inhibited neurogenic contractions in all three species in a concentration-dependent manner with pEC(50) values of 6.66 ± 0.11, 6.86 ± 0.06 and 5.71 ± 0.1 in human, mouse and rat respectively. In human bladder strips ICI118551 (100 nM) did not affect responses to fenoterol, while L-748337 (0.3-3 μM) produced rightward shifts of the concentration-response curves with a pA(2) value of 8.10. In mouse bladder strips ICI118551 (30 nM) blocked the inhibitory effect of fenoterol (pA(2)=8.80), while L-748337 (10 μM) inhibited the response with a pA(2) of 5.79. In rat bladder ICI118551 (30 nM) was without effect, while L-748,337 (10 μM) inhibited the response to fenoterol with a pA(2) of 5.40. From these results it is clear that fenoterol potently activates β(3)-adrenoceptors in human isolated urinary bladder to inhibit EFS-induced contractions. Fenoterol also activates β(3)-adrenoceptors in rat, but β(2)-adrenoceptors in mouse bladder to inhibit EFS-induced contractions.

The efficacy of tiotropium administered via Respimat Soft Mist Inhaler or HandiHaler in COPD patients

BACKGROUND

Tiotropium, a once daily inhaled anticholinergic delivered via HandiHaler, provides bronchodilation for >24h and improves patient-centred outcomes. The Respimat Soft Mist Inhaler (SMI), a novel, propellant-free inhaler, has been developed and proposed as an alternative delivery device for use with tiotropium.

METHODS

In a pre-specified, pooled analysis of two 30-week, double-blind, double-dummy, crossover studies, 207 patients with Chronic Obstructive Pulmonary Disease (COPD) were randomised to receive once daily tiotropium 5 microg or 10 microg (aqueous solution delivered via Respimat SMI), tiotropium 18 microg (inhalation powder via HandiHaler) or placebo. The primary endpoint was trough forced expiratory volume in 1s (FEV(1)) response. Forced vital capacity (FVC), peak expiratory flow rate (PEFR), rescue medication use, safety and pharmacokinetics (in a subgroup of patients) were also assessed.

RESULTS

Both tiotropium doses delivered by Respimat SMI were significantly superior to placebo and non-inferior to tiotropium 18 microg HandiHaler on the primary endpoint (all p<0.0001). All active treatments were significantly superior to placebo (all p<0.0001) and both doses of tiotropium Respimat SMI were non-inferior to tiotropium 18 microg HandiHaler on the secondary spirometry variables and rescue medication use. The systemic exposure was similar between tiotropium 5 microg Respimat SMI and tiotropium 18 microg HandiHaler but was higher for tiotropium 10 microg Respimat SMI. All active treatments were well tolerated.

CONCLUSIONS

Tiotropium 5 microg Respimat SMI is comparable with tiotropium 18 microg HandiHaler in terms of efficacy, pharmacokinetics and safety. Respimat SMI is an effective alternative, multi-dose delivery device for tiotropium.