Medication for Adults on autistic spectrum

My son is 21 with a diagnosis of autism and severe learning difficulties.  He lives at home with myself (his mother) and attends a day care centre Monday to Friday.  He is non verbal.

He goes through periods where he manages better than others.

For the last year he has been going through an extended period of not coping - increased sleeplessness, increased anxiety and starting to lash out at people - pushing and hitting.  This latter is a recent development.

He is receiving support from occupational therapist and speech and language therapist at the moment.

My query is re medication.  He is currently on 0.5ml Risperidone at night time which does assist in the sleeplessness.  However in the last year this medication is becoming less effective in dealing with his irritability and anxiety.

I would like to hear from other parents and carers with regard to the medication their adult autistic children are receiving, if it is helping and possible side effects being suffered?

Thank you

With regards

Ricki