Can you take effexor after you have been on tramadol for awhile. New med. Dr. gave.?

Yes but the dosages have to be monitored. tramadol and Effexor are closely related and thus pose a threat for serotonin syndrome when co-administered.Here are the facts.

Structurally, tramadol closely resembles a stripped down version of codeine. Both codeine and tramadol share the 3-methyl ether group, and both compounds are metabolised along the same hepatic pathway and mechanism to the stronger opioid, phenol agonist analogs. For codeine, this is morphine, and for tramadol, it is the M1 metabolite, O-desmethyltramadol. The closest chemical relative of tramadol in clinical use is Venlafaxine (Effexor), the SNRI. The two molecules are nearly identical. Both tramadol and Venlafaxine share SNRI properties, while Venlafaxine is devoid of any opioid effects.

http://en.wikipedia.org/wiki/Tramadol

Yes you can, and quite safely. Usually there is an overlap period when one med is reduced and another increased to the new dosage. If in doubt always consult your physician.

Cheers