Mydayis Use After Gastric Bypass
Mydayis (extended-release amphetamine) should be used with significant caution in patients who have undergone Roux-en-Y gastric bypass (RYGB), as the extended-release formulation may have unpredictable absorption and bioavailability in this altered anatomy.
Key Pharmacokinetic Concerns
The RYGB procedure fundamentally alters drug absorption through:
- Bypassing the duodenum entirely - the primary site where many drugs and their transporters are located 1
- Dramatically reduced gastric acid environment - affecting drugs requiring acidic pH for dissolution or activation 1
- Decreased absorptive surface area - potentially reducing overall bioavailability
Specific Issues with Mydayis
Mydayis is an extended-release capsule formulation that relies on controlled drug release over time. This presents several problems post-RYGB:
Extended-release mechanisms may fail in the altered GI anatomy, potentially causing:
- Erratic absorption patterns
- Subtherapeutic drug levels (treatment failure)
- Unpredictable peak concentrations
Evidence from similar medications: A case series demonstrated that extended-release formulations of psychiatric medications (including paliperidone) showed dramatically reduced drug concentrations post-RYGB, with one patient having a trough level of only 1.1 ng/mL despite steady-state dosing 2. The authors concluded that "oral extended-release drug formulations are particularly poor choices" in RYGB patients 2.
Clinical Recommendations
Consider immediate-release amphetamine formulations instead (e.g., Adderall IR, dextroamphetamine IR), which:
- Have more predictable absorption
- Allow for dose titration based on clinical response
- Can be given in divided doses throughout the day
If Mydayis Must Be Used:
- Monitor clinical response closely - watch for signs of under-treatment (poor ADHD control) or over-treatment (cardiovascular effects, insomnia, anxiety)
- Be aware that standard dosing may not apply - the altered pharmacokinetics make dose-response unpredictable
- Consider therapeutic drug monitoring if available, though reference ranges may not be established for post-RYGB patients
- Watch for the common Mydayis side effects that may be amplified: decreased appetite (30% incidence), weight loss (9%), insomnia (31%), and increased heart rate (9%) 3
Critical Monitoring Parameters:
- Cardiovascular: Blood pressure and heart rate at each visit (amphetamines increase both) 3
- Weight: Already at risk post-RYGB; amphetamines cause additional weight loss 3
- Nutritional status: RYGB patients require lifelong vitamin/mineral supplementation 4; appetite suppression from Mydayis compounds malnutrition risk
- ADHD symptom control: If inadequate, this suggests poor absorption rather than need for higher doses
Important Caveat
The FDA label for Mydayis contains no specific guidance for post-bariatric surgery patients 3, and no clinical trials have evaluated its use in this population. The recommendation for caution is extrapolated from:
- General pharmacokinetic principles in RYGB patients 1
- Case reports of extended-release psychiatric medications failing post-RYGB 2
- Known absorption issues with other medications in this population 5
The safest approach is to avoid extended-release formulations entirely in RYGB patients and use immediate-release alternatives that allow for more predictable dosing and titration.