[CPhTNoel]

I'm a pharmacy tech, so I'm familiar with these medications, but I had a concern that my pharmacist couldnt help with. My neice, who is 14, is currently taking two Adderall XR 20's for a dose of 40 mg every morning. She ran out over the holiday, so I filled the trial rx her doctor wrote for Vyvanse 70mg. I looked briefly at the information I had handy, and saw that the max dose for kids age 6-12 is 70 mg. I'm aware that the adderall is a combo of 4 different amphetamine salts, and that Vyvanse metabolizes in the stomach to dextroamphetamine. If my neice is on 40 mg of the combined amphentamine salts, with the dextroamphetamine being a portion of that dose, wouldnt 70 mg of the Vyvanse seem high?

edit: I managed to pull up the package insert of Adderall XR, theres a total of 20 mg dextroamphetamine in her current dosage, but since Vyvanse is a produg and turns into dextroamphetamine, how much of the actual dextroamphetamine will be in her system

[Mr. Lennon]

You ask a good question which any pharmacist should be able to answer. The first thing to understand is that Adderall contains half (+)-amphetamine salt and half racemic amphetamine salt. Racemic mixtures contain half (+) and half (-). Therefore, Adderall contains about 3/4 (+)-amphetamine and 1/4 (-)-amphetamine. When you factor in the molecular weights of the salts I think the total free base content is about 80% dextro. You can do the calculations for LDX dimesylate.Keep in mind that the Vicks inhaler contains (-)-methamphetamine as a decongestant. That gives you an idea of the stimulant potency of (-)-amphetamine. When you switch from Adderall to Vyvanse, you leave the (-)-isomer behind and go with pure (+). So, it is not possible to get an exact conversion. I would go with 70 mg of Vyvanse and 30 mg of Adderall being roughly equivalent. So, for a person getting 40 mg of Adderall, 70 mg of Vyvanse contains less amphetamine.

[CPhTNoel]

Thanks for the insight, we did go ahead and try the Vyvanse, as we had little alternative. It does not work as well as the Adderall does, but she didnt have any adverse reactions to it, which was my concern.