Table 2. IC₅₀ values for high K⁺ or carbachol induced contraction with PDE inhibitors in bovine tracheal smooth muscle.

Inhibitors	IC50 (μM)
	High K+	Carbachol
Vardenafil	100 <	17.9 ± 2.8
BAY 73-6691	72.1 ± 14.5	24.7 ± 3.2