effexor does work right away, i know zoloft, paxil, SSRI's take almost a month to kick in, this isn't the case with effexor. It must have been a high amount, b/c i am seriously ill from taking 300 mg. All I know is i felt normal, didn't have the residual methadone withdrawal crap, could sleep 8 hours, didn't have crazy dreams and everything else that goes along with opiate withdrawal.