Sm. Jankovic et al., Schild's equation and the best estimate of pA(2) value and dissociation constant of an antagonist, CROAT MED J, 40(1), 1999, pp. 67-70
Calculation of the pA2 value and dissociation constants for an antagonist f
rom the effects observed on isolated smooth muscles can be done in two ways
: using Schild's plot procedure or Schild's equation. In our study we used
the effects of muscarinic antagonists observed in experiments on isolated h
uman and feline stomach and rat gastric fundus. Only the estimates of pA2 v
alues and dissociation constants made using the Schild's equation on the ba
sis of the lowest antagonist concentrations were not significantly differen
t from the values calculated using the Schild's plot procedure. This sugges
t that, when it is impractical to perform the full Schild's plot procedure,
the best estimate of pA2 values and dissociation constants can be done wit
h the lowest antagonist concentration that significantly inhibits the effec
ts of an agonist on an isolated smooth muscle preparation.