Kim Kendall, PhD (drkimkendall.com): Stimulants for ADHD work very quickly, within a half hour to an hour and a half depending on the type and dose. They are really like wearing glasses in that sense. Strattera (atomoxetine) works more slowly and must be taken on a regular basis for a full effect. Ari Tuckman, PsyD, MBA (tuckmanpsych.com): The most effective and commonly used medications for ADHD are the stimulants — Vyvanse (lisdexamfetamine), Concerta (methylphenidate), Adderall XR (amphetamine and dextroamphetamine, among others) — and they begin to work within an hour. The short-acting versions last four to six hours and the extended-release versions last up to 14 hours, depending on the individual. I compare the stimulants to aspirin — they begin to work pretty quickly, do their thing, and then fade out so the medication is out of the person’s system by the next day. This allows people to have days when they take it and days when they don’t. Generally speaking, the extended-release versions are best because the person doesn’t need to remember to take a midday dose. Plus, they tend to be smoother in their effects through the day. There is also a nonstimulant medication called Strattera that needs to be taken every day and build up in the person’s system. As a result, it can be several weeks or more before it has any effect. The good news is that it works 24/7 once it kicks in. The bad news is that it tends to be less effective than the stimulants, so it is usually considered a second choice for ADHD. There is also a newer nonstimulant called Intuniv (guanfacine) that has some promise, but it hasn’t been out long enough to really know how well it works. David Pomeroy, MD (brainhealthnw.com): It depends on the ADHD medication. Stimulants work the same day, and only that day. Some take an hour to really be effective, others 15 to 20 minutes. It may take a few weeks to even a few months to get the medication type and dosages adjusted to the most effective amounts. Strattera and Intuniv may take anywhere from three to six weeks to see full effect, or at least one month after getting to the target dosage. It usually takes two to three weeks to increase gradually to the target. Charles Parker, DO (corepsych.com): Every ADHD medication works somewhat differently because of three things: One, genetic differences in rates of metabolism. Some burn slow and some fast based upon genetic differences in metabolic pathways. Two, metabolic differences: Some have a significantly slower onset of meds due to the slowing of liver activity associated with chronic bowel problems (constipated bowel, constipated liver, slowed burn rate). Three, medication differences: Sometimes, time-release meds show differences in onset of action based upon the construction of the medication itself. For example, Concerta sometimes varies in onset due to the variation in the immediate-release outer layer. The bottom line: Meds should start to work in 30 to 45 minutes.
