Hello,
There may be no side effects. Yet, whenever you're starting a medicine there could be tummy upset, loose poop, some 
tiredness as there is an adjustment. I find Zoloft occasionally causes some headache in the first week. Tenex can cause some 
dry mouth, and occasionally 
dizziness and fainting. 
Trazadone is similar in side effects - dizziness, tiredness, dry mouth. Ritalin's best known side effect is loss of appetite. Sometimes, a period of increased emotions in the early evening. Finally, Abilify can cause some increase in activity, 
restlessness and difficulty sleeping.
Finally, many of the medicines we use in children have been associated with an increase in suicidal thoughts. It's unclear if this is truly supported by research, or whether this is true because the medications help children to feel better and thus more able to tell you how they are feeling. This is quite a few medications and it may be hard to tell if there are any side effects. I would discuss anything you see that is different in your son with your doctors.
Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Lisa Baker, Pediatrician