Will Food Acidity Affect My ADHD Meds?

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Summary:

Lots of websites proclaim that acidic meals impair the absorption of Adderall, Ritalin, and other stimulant medications. Almost no research has been conducted that shows whether taking your morning pill with a glass of orange juice will really affect how much enters your body.

However, the basic physiology of drug absorption and excretion indicate that pH is an important factor. Amphetamine and methylphenidate are weak bases, and in highly acidic environments are more electrically charged, or ionized. That makes it harder for them to pass from the inside of the stomach or intestine into the cells lining the digestive system. However, when urine is more acidic, it is easier for the ionized form of the drug to pass into the urine and be excreted. So acidification can interfere with absorption and accelerate excretion.

On the other hand, far more drug absorption occurs in the small intestine than in the stomach. Even if the pH of the stomach is much more or less acidic than normal, this gets diluted very quickly along the meters and meters of small intestine, which excretes its own digestive juices. For many individuals, the acidity of their stomach becomes largely irrelevant then, to drug absorption.

Many people don't notice much impact from food acidity and the perceived potency of their stimulant medications. Some individuals, however, are quite sensitive. Immediate release formulations are more likely to be affected by stomach pH than are most slower release formulations, which have very little release into the stomach anyway.

However, some slow release medications, like Mydayis, have layers designed to dissolve only at a certain pH.

Separating pill intake from food by an hour or more may help if you are one of the individuals sensitive to this effect. However, the impact of antacids (histamine-2 blockers, or proton pump inhibitors) usually last for many hours, and can affect absorption throughout the day.

References:
Crosstalk of physiological pH and chemical pKa under the umbrella of physiologically based pharmacokinetic modeling of drug absorption, distribution, metabolism, excretion, and toxicity (2021)
https://www.tandfonline.com/doi/full/...

Lisdexamfetamine Dimesylate: Prodrug Delivery, Amphetamine Exposure and Duration of Efficacy (2016)
https://www.ncbi.nlm.nih.gov/pmc/arti...

Exposure from Extended-Release Stimulants: Results from the Concerta®, Adderall XR™ Food Evaluation (CAFÉ) Study (2008)
https://www.tandfonline.com/doi/abs/1...

Effect of omeprazole on gastric acid secretion and plasma gastrin
https://pubmed.ncbi.nlm.nih.gov/24913....

General:

Psychiatrist, neuroscientist, and author John Kruse, MD, PhD presents practical, actionable, well-researched information about treatment options that scientists and clinicians recommend for adult ADHD and other mental health conditions. Subscribe if you're curious about how neuro-atypical brains can optimize their functioning in our shared, and somewhat strange, world.

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