Methylphenidate (MPH) is available in 2 different isomer formulations. It is essential to know which formulation you are dealing with when converting from one stimulant to another. Those conversions are less precise if the new medication has a different formulation of isomers than the old one.

• 50% Dex and 50% Levomethylphenidate
  • Ritalin, Methylin, Ritalin SR, Methylin ER, Metadate ER,Ritalin LA, Metadate CD, Aptensio XR, Adhansia XR, Concerta, QuilliChew ER, Quillivant XR, Cotempla XR-ODT, Daytrana, Jornay PM, Medikinet
• 100% dexmethylphenidate
  • Focalin, Focalin XR

• The stimulants also vary in their duration of action, from 3-5 hours with Ritalin to 16 hours with Adhansia and Mydayis.
• If you are switching to a stimulant with a longer duration of action, you may need to raise the dose because it will be spread out over a longer period of time.

such as orally disentegrating ODTs (Adzenys, Cotempla), transdermal Daytrana, or delayed-release Jornay PM

• If the new stimulant has the same bioavailability and isomer as the old one, the conversion is complete
• Evekeo ODT has the same bioavailability as regular Evekeo and requires no adjustment

• All conversions are approximate,particularly when converting among different isomer mixes.
• For methylphenidate, most of the potency is due to it's dexIsomer, so you can convert from methylphenidate (which is 50%dex) to dexmethy|phenidate (100% dex) by cutting the dose in half.

Medikinet® retard and Concerta® are two MPH preparations with different release profiles and proved efficacy on ADHD symptoms as well as co-morbid conditions.

Medikinet

• Medikinet retard contains equal proportions of IR and slow release MPH. This once-daily extended-release formulation had a duration of action of about 8 hours in an analog classroom setting.
• Medikinet XL has a plasma profile showing two phases of active substance release, with a sharp, initial, upward slope similar to a methylphenidate hydrochloride immediate-release tablet, and a second rising portion approximately three hours later, followed by a gradual decline.
• When taken in the morning after breakfast, the immediate-release portion of the hard capsule dissolves rapidly and results in an initial peak plasma concentration. After passing through the stomach and into the small intestine, the sustained-release portion of the hard capsule releases its methylphenidate hydrochloride. This results in the formation of a 3–4-hour plateau phase during which concentrations do not sink below 75% of the peak plasma concentration^[1].
• The amount of methylphenidate hydrochloride absorbed when Medikinet XL is administered once daily is comparable with conventional immediate-release formulations administered twice daily.
• Medikinet XL may, therefore, be administered either as an intact capsule, or the capsule may be opened and the contents swallowed, without chewing, immediately after sprinkling onto applesauce or other similar soft food.

Concerta

• The tablet coating of Concerta dissolves within 1 to 2 hours and releases 22% of the total dose of MPH providing an initial maximum drug concentration at about 1 to 2 hours.
• The remaining 78% of the dose is osmotically controlled (osmotic-release oral system [OROS] technology) and released over 10 hours through a lazer-drilled hole.
• Peak plasma concentrations are achieved at about 6 to 8 hours, after which plasma levels of methylphenidate gradually decrease^[2]

Resources

• https://www.nepho.org/wp-content/uploads/2023/02/ADHD-Medication-Conversion-Chart.pdf
• https://www.psychiatrictimes.com/view/how-to-switch-stimulants-dosing-guide-for-adhd?slide=12