Effexor and Remeron are both out in generic. However, I have NEVER heard of antidepressants being give 3x daily, at least not the modern SSRI/SNRI ones.
There is a risk of what is caused "Serotonin Syndrome", a systemic illness caused by excessive serotonin that can occur when too many serotonin increasing drugs are taken or are taken in too high doses. This syndrome can be fatal.
One must be careful of many street drugs as well if they also act on the serotonin system in the brain. DXM and Tramadol are examples of drugs found on the street that can interact with antidepressants.
Tramadol actually has SSNRI activity in addition to its painkilling properties. DXM can be extremely dangerous to people taking modern antidepressants.
Please, get your son into the new psychiatrist as soon as possible so he can get his medications straightened out. Be aware that if he is currently taking very high doses of Effexor and is cut down, that he may go through withdrawal from the drug, which is supposed to be quite unpleasant. Remeron has a withdrawal if quit cold turkey but it's nowhere near as bad as Effexor. It's more like feeling really irritable and "strange" for a week or two, and if taking Remeron at night, possibly having difficulty sleeping.
The big thing right now is that if he is taking unsafe doses of Effexor, he has to either come off the drug entirely, or be tapered down to a safe dosage and scheduling.
Good luck with this