Your doctor should warn you of any possible interactions, but things that neutralize the medication may go to extremes. For example, grapefruit can alter your ability to metabolize drugs because it disrupts digestion and protein supply in the body. Another factor? Ascorbic acid in vitamin C can neutralize some medications used to treat Attention Deficit Hyperactivity Disorder (ADHD).
How do medicines for ADHD work?
“It’s an inaccurate generalization to say that ‘vitamin C interacts with ADHD medication,'” says Whitney Prude, PharmD, BCPS, an NBC-HWC board-certified clinical pharmacist in Rochester, Minnesota. This is because not all medications for ADHD have similar mechanisms for how they work in the body.
However, to understand why vitamin C impairs the effectiveness of one type of ADHD drug (known as amphetamines), we need to understand ADHD at a neurological level. “We have a very complex network of nerves (estimated at about 100 billion) that connect all the different parts of the brain and allow them to communicate with each other,” says Dr. Proud. “Between each nerve connection, there is a gap; within this gap, there are many different chemicals that pass from one nerve to another to deliver a message and trigger a response that passes to the next nerve and the next.”
When there is any kind of dysfunction in the brain that changes the passage of these chemicals, we begin to see changes in behavior, he explains. ADHD is still being studied, but for now, Dr Proud says 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 in many other functions, such as memory, movement, motivation, mood, attention, etc. In ADHD, there is a deficiency of dopamine and norepinephrine resulting in the reduction of many of these functions.
How Vitamin C Affects Medicines For ADHD
The most common medications for ADHD are known as stimulants. These stimulants work by causing an increase in dopamine and norepinephrine in the aforementioned brain cavities. This makes your brain function as if more dopamine and norepinephrine are available, which in turn relieves the symptoms of ADHD.
However, many medications for ADHD are not stimulants at all and some stimulants have a different physiological process that is not affected by vitamin C such as methylphenidate (also known as Ritalin). The drugs that is affected are called amphetamines and are often known by brand names such as Adderall, Adderall XL, Dyanavel XR or Vyvanse.
“The interaction between vitamin C (ascorbic acid) and amphetamines occurs when they are present in the stomach at the same time,” says Dr. Proud. “Vitamin C is an acid and amphetamines are a base or alkaline composition. When these two combine, they form a salt compound. This combination then becomes indigestible and cannot be absorbed into the bloodstream.”
So, if you are taking an amphetamine preparation for a drug for ADHD, Dr. Prude advises you to avoid taking vitamin C for an hour before and after taking it. And, of course, if you have any questions or concerns, you should discuss them with your provider.
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