Meteprolol when taken with Bupropion have a interaction which increases the plasma concentrations of Metoprolol (amount of drug available in blood at a given time),but this is not a potential interactions which may not cause severe side effects.
But as you mentioned,you have been under Metoprolol tart-25 mg, which suggests that it is a extended release formula whose duration of action is extended from 10 hr to 14 hr, in case of severe Hypertension.But generally Metoprolol standard formula is started as initial therapeutic dose as 50 mg where your Met-25 mg is way too low dose for causing any potential fatal effects.Bupropion is advised for smoking cessation mainly but also for depression.
But your situation with obstructive sleep apnea may need complete evaluation to isolate underlying condition such as Congestive Heart failure or Cor Pulmonale or Obstrutive sleep apnea syndrome with neurosis and depression which further increases the risk of developing Cardiovascular disease etc,also any other condition of body.
So,what are the other symptoms do you have?What are the timings that you take these medications?What are the investigations done before prescribing these medications? What is the medical condition that was confirmed by your Doctor before or after prescribing?Were you suffering from Sleep apnea alone or do you have any undiagnosed Hypertension, anxiety,smoking,alcoholism,depression,obesity,Diabetes issues?
Please do not be worried!But have an complete evaluation done with your Doctor and keep us updated.God Bless!