Hello, I checked my supplement guide and did not see that Wellbutrin affects lactic acid threshold but it can behave as a stimulant in some people and some of the side effects are agitation, sweating and insomnia. Increased sweating can put you at risk for an electrolyte imbalance. Make certain you replace all fluids lost during exercise by weighing yourself before your workout and right after your workout. Drink about 1 Liter of Gatorade/sports beverage per pound lost. If you feel better then your theory was correct, if not please mention this to your prescribing physician along with any other symptoms you may be experiencing. Thank you for coming to HCM!