Hi E.,
It really is so frustrating trying to find the right product that will made headway for each individual. I started getting acne at 21 and have been dealing with it for two decades, although now at 43, it's much less frequent, thankfully. The thing with each product is that you need to give it 3 months to see if it works for you or not. That is hard to do, I know, when you just want it all to go away. But I'm sure you've heard that from your derm, too. I personally have been on doxycycline, minocycline, tetracycline, cleocin and a few others that I've forgotten the names of. So both topical and oral. I haven't taken the oral prescriptions in years, but that is what my derm started me out with in my early 20s.
I personally would be very, very leary of starting your son on accutane. I know that there are some who say it saved their lives, but I think the risks are far too great.
I would start your son on a Salicylic acid face wash. There are many over-the-counter products out there. And then I would try a glycolic product (alpha hydroxy). They treat acne by helping to remove dead skin cells and helping to reduce inflammation. Alpha hydroxy acids also stimulate the growth of new, smoother skin, which helps reduce the appearance of acne scars. This is my all-time favorite product with this ingredient and it is well worth the money spent. You only use a large pea size for your entire face, so my bottle lasts me a good 6-8 months.
http://www.neostrata.com/product/neostrata+oily+skin+solu...
Finally, he'll need an effective spot treatment. Honestly, there is nothing better than good old benzoyl peroxide. Your derm can prescribe a higher dose than is available over-the-counter. Do not have him apply this product liberally, just dot it onto cysts.
Also, I used to go to the doctor who created benzoyl peroxide, Dr. Fulton. Dr. Fulton often used ice cube therapy on cystic acne (those are the deep, painful lesions that typically do not have a white head). Have your son hold the ice cube on each lesion for 2-3 min. (or the doctor use to freeze ice into styrofoam cups and then you can peel the cup down as the ice melts and you can cover more area of the face this way faster). I like using the ice cube method right after I cleanse my face and before I use any other product. The ice cubes reduce the acne inflammation and then you apply the glycolic product, then the benzoyl peroxide.
Of course with use of the glycolic and benzoyl products, he will need to stay out of the sun and use a sunscreen on his face. I personally use Blue Lizard Face and I never have any problems with it making the acne worse:
http://www.drugstore.com/blue-lizard-australian-sunscreen...
You may also want to do a little research on food items that can cause and inflame acne. There's a lot of info on the internet. Dairy, glutens and food products w/ iodine (shrimp, etc.) can cause flare-ups.
Good luck. Finding the right products for your son's skin will be trial and error; the above has worked for me.