Interesting, I get the output below.
Perhaps restart your R session (Session >> Restart R)?
library(RxODE)
ode <- "
C2 = centr/V2;
C3 = peri/V3;
d/dt(depot) =-KA*depot;
d/dt(centr) = KA*depot - CL*C2 - Q*C2 + Q*C3;
d/dt(peri) = Q*C2 - Q*C3;
d/dt(eff) = Kin - Kout*(1-C2/(EC50+C2))*eff;
"
m1 <- RxODE(model = ode)
print(m1)
#> RxODE 0.7.2-5 model named rx_d5b1308db9def0736dc9e914735853cc model (✔ ready).
#> $state: depot, centr, peri, eff
#> $params: V2, V3, KA, CL, Q, Kin, Kout, EC50
#> $lhs: C2, C3
Created on 2018-07-10 by the reprex package (v0.2.0.9000).