The effect of inhaled fenoterol and ipratropium bromide on propranolol induced bronchoconstriction in the asthmatic airways.
1. The provocative dose of inhaled propranolol, (PC20P, mg/mL) needed to induce a 20% reduction in the forced expired volume in 1 s (FEV1, L) was determined for 15 adult asthmatics following randomized pre-treatment with placebo, ipratropium bromide (40, 160 micrograms) and fenoterol (200, 800 micrograms) aerosols using a double-blind protocol. 2. Fenoterol 200 micrograms, 800 micrograms increased the baseline FEV1 0.28 +/- 0.16, 0.32 +/- 0.16 L (P = 0.04, P = 0.008 respectively). Fenoterol 800 micrograms moved the PC20 P rightwards from placebo geometric mean 10.95, 95% Confidence Intervals (95% CI) 4.43-27.22 mg/mL to mean 20.41, 95% CI 10.13 to 40.64 mg/mL (P = 0.01). Fenoterol 200 micrograms was not protective; mean PC20 16.22, 95% CI 7.83-34.35 mg/mL (P = 0.08). Neither 40 or 160 micrograms ipratropium changed the FEV1 or PC20P values compared with placebo; increase in FEV1 0.15 +/- 0.27 L (P = 0.22), 0.24 +/- 0.12 L (P = 0.14) and geometric mean PC20P 16.59 +/- 0.57 mg/mL, 95% CI 8.01-34.51 mg/mL (P = 0.90), 15.58 +/- 0.66 mg/mL, 95% CI 6.72-36.05 mg/mL (P = 0.34) respectively after ipratropium treatments. 3. Bronchoconstriction induced by inhaled propranolol (P) appears to be only weakly antagonized by inhaled beta-agonist and not reduced by antimuscarinic anticholinergic aerosol. This finding argues against the activation of a cholinergic reflex to explain propranolol induced bronchoconstriction (PIB).
Latimer
K M
KM
Department of Respiratory Medicine, Flinders Medical Centre, Bedford Park, South Australia.
Ruffin
R E
RE
D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology*; D016084:Bronchoconstriction / Q000187:drug effects*; D004311:Double-Blind Method; D005260:Female; D005280:Fenoterol / Q000494:pharmacology*; D006801:Humans; D009241:Ipratropium / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D012129:Respiratory Function Tests
D005280:Fenoterol; D011433:Propranolol; D009241:Ipratropium