Comparison of the protective effect amongst anticholinergic drugs on methacholine-induced bronchoconstriction in asthma

The protective effect of inhaled anticholinergic drugs in the methacholine-induced bronchospasm is well-known. The objective of this study was to assess if any possible differences may be found among Ipratropium (IB), Oxitropium (OXI) and Tiotropium (TIO) pre-treatments to obtain the protective effect. Forty-four patients with intermittent bronchial asthma and PD20FEV1 < 200 mu g were selected (24 M, 20 F; mean age 32 +/- 8.8). On the baseline, they had mean FEV1%: 98.8 +/- 8.54 of theoretical and mean PD15FEV1 111.8 +/- 61.04 mu g. After 72 hours, all patients underwent a second methacholine challenge and were given Ipratropium (40 mu g by MDI in 14 pts) or Oxitropium (200 mu g by MDI in 14 pts) or Tiotropium (18 mu g by Handihaler in 16 pts) sixty minutes before the test. Sixty minutes after the bronchodilator inhalation, the FEV1% increase was higher (p < 0.05) in OXI (6.7 +/- 4.83%) and TIO groups (6.11 +/- 2.54%) than in the IB group (3.8 +/- 1.96%). In the IB group PD15FEV1 and PD20FEV1 were obtained in all patients, while in the OXI group they were obtained in 12 and 5 pts respectively and in the TIO group in 14 and 5 pts respectively. Normal hyperreactivity was obtained in 2 patients, in both OXI and TIO groups. In OXI and TIO, the PD15 obtained after drug pre-medication, was similar (respectively 1628 +/- 955.7 and 1595.5 +/- 990 mu g), but higher (p < 0.0001) in comparison to the PD15 measured in the IB group (532.2 +/- 434.8 mu g). Also, the dose-response slope (decline percentage of FEV1/cumulative methacholine dose) after PD15 was similar in both OXI and TIO groups but different in the IB group. A significant relationship (p < 0.01) was found between PD15FEV1 (obtained in 40 pts) and the increase in FEV1% obtained 60 minutes after bronchodilator inhalations (r = 0.53). In conclusion, with a standard dose, both Oxitropium and Tiotropium seem to have the same protective effect in bronchial asthma but higher than Ipratropium. It's probable that the best dose of Ipratropium should be a higher one than the usual dose taken.