First: who is making the diagnoses on these kids? It's vitally important to get an accurate diagnosis after appropriate test batteries have been done. A pediatrician or GP is NOT qualified to make these dx...it takes a complete neurological and psychiatric evaluation to rule out other causes of the behaviors. A reputable neurologist will usually have a counselor for referrals, one who is trained in dealing with ADD, ADHD, and ODD. Don't settle for less. Your kid's future could be at stake.
Several other emotional/psychological problems share symptoms with ADHD and its neurological siblings. It's vital to let the right professionals make the diagnosis, and to use the services of the right counselors to help you make the lifestyle/parenting modifications that will work for your kid. Otherwise you could be wasting your time, money,and energy on the wrong interventions and treatments.
I don't understand why doctors are giving these kids Paxil and tranquilizers. These are not the first-line drugs for treating these disorders. Don't just accept scripts without asking lots of questions, like"why THIS drug? What do you expect this drug to do?"
It's also vitally important that you NOT get lost in dealing with your child's problems. You may find you need to grieve and mourn for your hopes for a 'normal' life for your challenged child. You also need to balance that child's needs against those of your other kids.
There is no shame in hospitalizing an out-of-control child if you can't cope any other way, especially when the ODD results in violent behavior. So long as the experience includes more than restraint and drugging, it could be helpful.
I heartily suggest FAMILY therapy, not just individual therapy. It can help you all learn coping skills, and it involves the whole family in the process of making a life around the child's disability (and it is a disability.) The other kids may feel helpless or overwhelmed, and family therapy will give them a voice and an outlet for their frustration. It can also help you to find a reasonable perspective when you feel like all you can see is your kid's problems.
It's a painful fact that a huge percentage of ADHD and ODD kids never learn successful life management skills. It's not anyone's fault, so don't waste your precious time assigning blame anywhere. It's just one of those hard facts we parents of brain-damaged kids have to accept. (accepting that these neurological glitches are brain damage is hard for some of us, and it's pc to use pretty euphemisms, but facts is facts, and dressing 'em up in pretty packages won't change 'em.)
As for the ADD/ADHD/H thing, be aware that any ADHD kid can concentrate for a long time on something he finds interesting (like video games). It doesn't mean they are faking when their attention sputters and fades at difficult or boring tasks. Also hyperactivity and poor attention span can result from many other sources than the brain dysfunction that characterizes genuine ADHD. Again, proper testing is necessary. When in doubt, get a second opinion. Even doctors can be misinformed about these disorders.
I heartily recommend parents join an advocacy/support group. You can find wonderful resources for parents online. My contact info is probably too old to be useful; my kids have been out of school for years. (and yes, they still at 23&24 are unable to hold a job and stay out of trouble; with the best goodwill in the world they continue to screw up their chances and get into scrapes. If you take it personally, it will kill you. You have to learn to keep them and their probs in some perspective. Don't forget to take care of YOU too.)
I wish you the best in dealing with your children. Let me know if I can help you find resources. YOU ARE NOT ALONE!