Your doctor should warn you about any potential interactions, but things that neutralize medications can fall through the cracks. For instance, grapefruit can alter your ability to metabolize drugs because it disrupts digestion and protein delivery in the body. Another factor? The ascorbic acid in vitamin C can neutralize certain medicines used to treat attention deficit hyperactivity disorder (ADHD).
- Whitney Prude, PharmD, BCPS, NBC-HWC, Dr. Whitney Prude is a board-certified clinical pharmacist in Rochester, Minnesota.
How do ADHD medications work
"It is an inaccurate generalization to state that 'vitamin C interacts with ADHD medication,'" says Whitney Prude, PharmD, BCPS, NBC-HWC board-certified clinical pharmacist in Rochester, Minnesota. This is because not all ADHD medications have similar mechanisms for how they work in the body.
However, to understand why vitamin C disrupts the efficacy of one type of ADHD medication (known as amphetamines), we need to understand ADHD at a neurological level. "We have a very complex network of nerves (estimated to be around 100 billion) that connect all the different parts of the brain and allow them to communicate with one another," says Dr. Prude. "Between each nerve connection, there is a gap; within this gap, there are many different chemicals that pass from one nerve to the next to deliver a message and trigger a response which passes to the next nerve and the next."
When there is any sort of dysfunction in the brain that alters the passing of these chemicals, we start to see changes in behavior, she explains. ADHD is still being studied, but for now, Dr. Prude says that two of the chemicals in the brain that contribute to ADHD symptoms are norepinephrine and dopamine.
Norepinephrine is responsible for increasing alertness, arousal, and attention, while dopamine plays a role in our "reward center" and many other functions, including memory, movement, motivation, mood, attention, etc. In ADHD, there is a deficit in dopamine and norepinephrine resulting in the decrease of many of these functions.
How vitamin C affects ADHD medications
The most common ADHD medications are known as stimulants. These stimulants work by causing an increase of dopamine and norepinephrine in the aforementioned brain gaps. This causes your brain to function as though more dopamine and norepinephrine are available, which in turn alleviates symptoms of ADHD.
However, many ADHD medications are not stimulants at all, and some stimulants have a different physiological process that isn't affected by vitamin C like methylphenidate (aka Ritalin). The medications that are affected are called amphetamines and are often known by brand names like Adderall, Adderall XL, Dyanavel XR, or Vyvanse.
"The interaction between vitamin C (ascorbic acid) and amphetamines occurs when they are present in the stomach simultaneously," Dr. Prude says. "Vitamin C is an acid, and amphetamines are a base or alkaline formulation. When these two come together, they form a salt compound. This combination is then rendered indigestible and cannot be absorbed into the bloodstream.”
So if you are taking an amphetamine formulation of an ADHD medication, Dr. Prude advises that you avoid consuming vitamin C for one hour before and after taking it. And, of course, if you have any questions or concerns, you should chat them through with your provider.
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