My thought is that DH is being ridiculous and making this a competition with BM, which is harmful to his daughter. He might just need to accept that he isn't going to get his way on this one, and acting this way makes him no better (in fact, worse) than BM.

I wonder what the doctor said about the meds. Our doctor said SS can have the med vacation when his focus is not required (e.g. if the kid is to watch TV all day then he doesn't need the meds). We don't intentionally ask him not to take it just to mess with BM...although, most of what SS did at her house is just to watch TV all day.

If your SD's doctor said the meds should be taken daily then there is no "parental preferences" on whether she should take it or not. 

Not knowing the entire situation, but it's not usually typical to give one parent sole legal...they usually only do that when the other parent is displaying poor life choices. I could be wrong on that, but here in CA we are 50/50 unless there are extenuating circumstances.

I don't think it's good practice by your DH to be doing what he is doing, has he spoken to his child's doctor about any of this? Also is he doing any other sort of alternative therapy on his own time to deal with the ADHD that doesn't require medication that he could prove is having actual success to the court system?

One critical success factor for many meds is consistent dosing times and quantities which maintain consistent levels of meds in the system.  Dad in this case is not doing his kid any service and may even be actively sabotaging this kids health.

Though not psycho active or behavioral treatment meds, I am on meds 24/7 and have been for nearly 40 years.  As a T-1 diabetic my head has nearly exploded any number of times when I have seen both adult T-1s and the parents of child T-1's take "breaks" from their insulin or following the "eat what you want and take a ton of insulin" model.  This is just insane.  

I had a few incidents while in HS when parents of a T-1 would drop their kids off at Military School and those kids would completely lose the plot on what they were eating and on often either not taking their meds or OD'ing on insulin.  As the Sr. Cadet officer/resident T-1 myself I was the one called for diabetes crisis.  I got a regional life saving award from the JROTC for one incident.  

My point is... people need to take their damned meds as Rx'd by Doctors.  My SIL (bros wife) is one who does not like meds for either herself or her kids and would give her kids only half the dosage Rx'd if at all, would do weeds, oils, crystals, etc...as her go to treatment of just about anything.  Two years ago she was Dx'd with breast cancer.  It was very interesting how quickly she got on board complying with her Doctor's prescribed medications and got rid of the holistic useless crap she had tortured her kids with all through their childhoods.  I was often shocked by my brother's tolerance of the tortures his wife put his kids through.  He finally got to where he would take his kids to a real Doc and give them their meds without sharing that with his wife until they had recovered and his wife would prance around about how healthy eating, living, weeds, oils and crystals had dealt with the kid's illness.  At which point my bro would hand her the empty Rx bottle and give her clarity.  We would watch their kids upon occasion and more than once he give me their meds in a side bar conversation.

I am fully supportive of parents owning the health and medical treatment of their kids... as long as the parents actions do not jeopardize the health of the kids.

All IMHO and experience of course.

I have many problems with this. Your DH is teaching your SK that it is okay to not follow doctor's orders. Also, "keeping it a secret", or literally turning a blind eye from BM isn't healthy either. This will only lead to more deception and SK thinking rules do not apply to them. 

If DH is concerned about the side effects, he needs to sit down with the doctor, BM and SK. Law needs to be laid down about how the benefits are outweighing the risk. I'm sure the doctor will have tips and tricks, even tweaking the dose, to help out. Being open and transparent about it is the best route. Also, hate to say it, but this is NOT your DH place to decide whether she takes it or not. BM has medical rights and he needs to respect it. 

Lastly, why does SK even know DH is against it? She should not know ANY of this. Is DH bringing up the issue or has she overheard?  It only creates a dad vs. mom attitude even more and pushing SK to "choose sides." He is putting his kid in a loyalty bind. 

It is not unusual for kids to toss their ADHD meds. Some will stick them in key holes IN the door knobs. Others will stick them down ac vents in floor,,,or squish them between window and widow sills.  I work several cases like this.

Moms that are hyper pissed about this, should be checked.

WHY is BM so mad and wants to take dh back to court. Is it that  BM  needs that on going prescription so SHE can use them too,  Moms use their kids ADHD meds to self medicate (buzz), some sell it too. You would be very surprised the up tics of use OR is mom unable to cope without kid being zoned out??

You can always have skid re-checked by a different doc, diagnosis may be kid does not have adhd, OR maybe she does. . ADHD can be treated without meds that give adults a buzz. Did you try a Patch?

**  Based on several true stories**.

My DH started taking ADHD meds when he was a young child, by the time he was a young adult (around 14), he refused to take them because they made his hands shake. I think once a child reaches a certain age, you can't force them. 

He now takes ADHD meds only when he's working. He doesn't notice any negative side effects when he doesn't take them and they continue to help him while he's working. I sometimes notice when he's not taking them, however. 

One SS takes ADHD meds, probably since around the same time as DH. He has never brought any with him on visitation weekends. 

All that is to say, that not taking ADHD medication on weekends should not be harmful to the child. 

However, I agree with the posts above that the lying is an issue. Your DH shouldn't be putting the child in the middle. 

Personally my mood is worse for a couple of days when I stop taking my ADHD meds (mild withdrawal symptoms). I would rather take them full time than only certain days. 

My concern about one half of a blended family not maintaining the SKid taking ADHD meds on their time is that it is far too tempting a manipulation technique to send the kid back to the other home an unmedicated PITA.

In this type of thing both sides must support the best interests of the Skid as the sole priority far above torturing the opposition.

If I had a kid that required meds daily and the other side of the blended family equation could not be trusted to make that happen, I would not send the kid. PERIOD!  If I was forced to send the kid by the courts, that kid would immediately go to their doc for tests to prove that the toxic opposition continued the meds. If they didn't, I would be in court shredding the side that jeopardized the kid's wellbeing and  jumping on the Judge's bench. Figuratively of course.

I may be a bit sensitive to this topic because of my own medical conditions that require constant medication.  If my insulin pump fails, I go from feeling great to feeling like hammered dog shit in a hurry.  Which is why I use an continuous glucose monitor and test my blood regularly to catch any issues before they cause me to suffer the consequences of either high or low blood sugars.  My Endo team teases me about how often I test my blood even while using a CGM system. I am fine with that.  I am also the first patient they call when they want to try a new related technology. They know I am going to test 8-12+ times a day regardless of the claims of the new wonder technology that eliminates or significantly reduces the need to perforate myself for blood tests.  I am a data guy.