Accutane is a derivative of vitamin A, so any multivitamins with vitamin A should be avoided. Accutane can also have an effect on the liver, such as increased liver function tests, so any medication, such as for example oral antifungal medications or methotrexate, or substance, such as alcohol that affects the liver adversely should be avoided. Acetaminophen (panadol) is one such medication. The list of such medications is long. If you are prescribed a new medication, please have the prescribing doctor know you are on Accutane so that they can check that there are no cross-reactions or adverse effects of taking those two medications together.
As far as sibutramine is concerned, I would probably not recommend that my patients take that together with Accutane. Some of the side effects of sibutramine can also be seen with Accutane, so it would be difficult to sort out if you should have such a reaction.
In addition, sibutramine can cause anxiety, extreme excitement, nervousness and depression. Accutane can potentially cause mood swings. I would be very cautious with two medications that both can affect mood stability. I would advise my patients against it.