Divalproex sodium ER is a hydrophilic matrix tablet that requires a low pH to dissolve. Switching to an IR formulation bypassed the need for a low pH and the VPA was delivered and absorbed. Mr. G was always able to absorb the medication, but only when delivered. The Table lists other psychiatric medications that clinicians should be aware of that utilize similar hydrophilic matrix technology to slowly release medications through the gastrointestinal tract and also require low pH to release the medication from the tablet.
OUTCOME Stable once again
Two and a half weeks after his medication formulation is changed from divalproex sodium ER to IR, Mr. G shows improvement in his symptoms. His serum VPA level is 52 µg/mL, which is within therapeutic limits. He continues receiving his previous medications as well. He reports “feeling much better” and denies having any depressive symptoms nor anxiety. Mr. G is able to maintain eye contact, and has positive thought content, improved organization of thinking, and retained abstraction.
Bottom Line
All medication changes should be identified at each visit. Many extended-release psychiatric medications require lower pH to release the medication from the tablet. When evaluating nonresponse to psychotropic medications, anything that affects pH in the stomach should be considered.
Related Resources
- Monte SV, Russo KM, Mustafa E. Impact of sleeve gastrectomy on psychiatric medication use and symptoms. J Obes. 2018; 2018:8532602. doi: 10.1155/2018/8532602
- Qiu Y, Zhou D. Understanding design and development of modified release solid oral dosage forms. J Validation Technol. 2011;17(2):23-32.
- ObesityHelp, Inc. https://www.obesityhelp.com/medications-after-bariatric-surgery-wls/
Drug Brand Names
Bupropion • Wellbutrin, Zyban
Clonidine ER • Kapvay
Divalproex sodium extended- release tablets • Depakote ER
Escitalopram • Lexapro
Iloperidone • Fanapt
Methylphenidate ER tablet • Concerta
Methylphenidate ER capsule • Metadate, Jornay
Methylphenidate LA capsule • Ritalin LA
Mirtazapine • Remeron
Omeprazole • Prilosec, Zegerid
Paroxetine • Paxil
Valproic acid immediate- release capsules and solution • Depakene
Valproate sodium IV • Depacon
Venlafaxine • Effexor