My experience is very similar. I was 125 lbs when I started taking Paxil for anxiety and gained about 40lbs over the course of 2 years. I started on Wellbutrin at the suggestion of my Dr. when I advised that I no longer wanted to take it due to the horrible weight gain. I took effexor and buspar together worst time of my life!! I'm 33 year old female was rushed to the ER due to serotonin syndrome never will I take effexor again. A: According to the prescribing information for Effexor (venlafaxine), your health care provider should periodically reassess the need to continue its use during long-term treatment with Effexor. I am a 63 year old female who has been on Effexor for many years. I take it for anxiety. I never knew some of these side effects. Naughty me, I didn’t read the info supplies. Effexor is a dual purpose antidepressant released by Wyeth-Ayerst Laboratories and approved by the FDA in October 1997. Effexor boosts serotonin levels in the synapse in similar fashion to other SSRI's. I have been on Pristiq for a year (50mg, then 100mg) and have had pretty significant weight loss from steadily experiencing low/no appetite, nausea, diarrhea, and vomiting. Taking 5-HTP supplements may help you lose weight by reducing your appetite and cravings for carbs. 5-HTP supplements increase serotonin levels in the brain, and serotonin naturally suppresses your appetite, helping you eat less, explains The Oz Blog. I am on Effexor cause I have Major Depression. Some people gain weight on it and others lose weight on it. Before starting Effexor I weighed 145lbs then 130lbs I lost weight no matter what I ate. Have been on Effexor or similar medication for 20 yrs. Condition was getting worst, doctor increased medication, finally i have decided to get off the Effexor, doctor had no comment, offered no help. Withdrawal Symptoms. Methadone is a synthetic opioid designed to be effective over several days. Withdrawal from methadone can be very difficult because the drug is able to stay in the system for several days, prolonging the detox process.