Are these episodes happening in a similar time frame? For example, do they tend to happen as the dose is wearing off and right before another dose, or do they tend to happen when the ritalin is at its strongest (about an hour after taking the medication)? There's something called a "rebound effect" where the child goes from having too much ritalin in his system to too little ritalin, and the behavior bounces around accordingly.
In general, what was his behavior like before Ritalin? What you describe is pretty extreme behavior for a 6 year old. Before Ritalin, what were the main complaints the teachers had that caused a diagnosis to be sought for him?
(I have a now 23 year old who was on Ritalin all his elementary school days, and in some ways I regret it, but I don't know how he could have maintained focus if he weren't on it. It was a small dose - highest was 5 mg per day, but I still wonder if he could have learned to force himself to focus if he was treated behaviorally instead).
Doctors always start a child off on the lowest dose and then up the dose if it doesn't change the behavior.
Basically if his behavior has basically stayed the same, it would mean the dose is not high enough. If his behavior has gotten worse, it would indicate that the med is making it worse - which could mean that he does not have ADHD. Of course, there could be other things going on that would make his behavior worse. So you can't go by just one day.
What his parents do need to do is to let the doctor know what is going on. Don't wait till the end of the month.
I am curious as to how old the child is and what kind of a doctor he is seeing for this? Also, I am the CL over on the ADHD forum and if you need any resources about ADHD and how to work with the child - feel free to also post over there.
if he is bipolar take him off of the stimulant and get him onto a sedative used for add and a mood stabilizer. also consider something to help him sleep if he does not sleep well.
bipolar disorder is often times confused for many different things. and some doctors don't like to diagnose people with it, especially young people.