Phentermine vs. Adderall: 5 Differences Between These 2 Stimulants

Phentermine (Adipex-P, Lomaira) and Adderall (mixed amphetamine salts) are both stimulant medications. But they serve very different purposes. Phentermine is best known as a short-term appetite suppressant for weight loss. Adderall is widely prescribed for attention-deficit hyperactivity disorder (ADHD).

Both medications influence similar chemicals in the brain. But they come with distinct risks, benefits, and prescribing guidelines. Here are five differences between phentermine and Adderall to know.

1. Phentermine is approved for weight loss, while Adderall is approved for ADHD and narcolepsy

One difference between phentermine and Adderall is their approved uses. Phentermine is FDA approved to be taken short term for weight loss in people with a larger body size. Adderall is approved to treat ADHD. It’s also used for narcolepsy, a sleep condition that can cause excessive sleepiness during the day.

Phentermine helps with weight loss. It’s thought to do this by decreasing appetite and increasing energy use. Adderall can have a similar effect, but it’s not approved for weight loss. Even so, it’s sometimes prescribed off-label to help people lose weight. But Adderall has specific risks to consider. We’ll cover those later.

2. Phentermine and Adderall are both stimulants, but they have slightly different effects

Phentermine and Adderall are both stimulants. This means they boost the activity of the brain and nervous system. They increase levels of key brain chemicals, such as norepinephrine and dopamine. But their effects on these chemicals differ slightly.

Adderall contains amphetamine salts. Amphetamines primarily increase levels of dopamine and norepinephrine in the brain. The dopamine increase is associated with motivation and reward. Norepinephrine enhances alertness, attention, and focus. This combination helps improve focus and concentration in people with ADHD. It also helps those with narcolepsy stay awake during the day.

Phentermine’s chemical structure is similar to amphetamine’s. But they’re not the same thing. Phentermine primarily increases norepinephrine levels. This helps reduce hunger signals in the brain so you eat fewer calories. It also increases dopamine, but to a lesser extent than Adderall. So phentermine doesn’t provide the same cognitive benefits.

3. Phentermine is approved for short-term use, while Adderall can be taken long term

Another difference between phentermine and Adderall is how long you may take them. Phentermine is approved to be taken short term — usually 12 weeks (3 months) or less. Adderall is often taken for years as a treatment for ADHD or narcolepsy.

Phentermine is approved for short-term use. This is because there was limited long-term safety data available at the time of its approval. It’s also possible to develop tolerance to phentermine. This means that its effects can lessen over time. In this case, you may be told to stop taking phentermine if you’re no longer responding to treatment.

EXPERT PICKS: WHAT TO READ NEXT

• Phentermine side effects: Do you have dry mouth after taking phentermine? Find out about potential phentermine side effects and how to manage them.

• Adderall dosage: Learn more about typical Adderall dosages for adults and children, plus steps to take if you miss a dose or take too much.

• Injection vs. pill: Explore how Wegovy (semaglutide) and phentermine compare for weight loss.

But you may be prescribed phentermine beyond 3 months if it’s working for you and side effects aren’t an issue. Recent research suggests that phentermine may be safe and effective when taken longer than 3 months. Qsymia is a weight-loss pill approved to be taken longer term. It contains phentermine and topiramate.

How long you’ll take Adderall can depend on your situation. ADHD and narcolepsy tend to be lifelong conditions, with symptoms appearing differently over time. Your healthcare team may have you continue or stop Adderall. This will depend on your treatment needs.

4. Phentermine and Adderall are available in different dosage forms

Phentermine comes in tablets and capsules but also a variety of other formulations. These include low-dose tablets (Lomaira), orally disintegrating tablets (ODTs), and a combination pill (Qsymia). Adderall is available in both immediate-release (Adderall IR) and extended-release (Adderall XR) capsules. Only Adderall IR is approved for narcolepsy.

Phentermine’s different formulations provide options to help meet your specific needs. Lomaira is a lower-dose alternative, while Qsymia provides a combination approach to weight loss. And if you have difficulty swallowing pills, the ODT comes as a tablet that you dissolve on top of your tongue. Extended-release phentermine has been discontinued.

Adderall IR requires multiple doses per day, but it can offer flexibility with how often you take a dose. Adderall XR is taken once daily in the morning, providing longer-lasting effects. It can be a good option if you prefer taking fewer pills.

5. Adderall has a higher risk of dependency and misuse compared with phentermine

Phentermine and Adderall are both classified as controlled substances. This means that they have a risk of dependency and misuse. But these risks are higher with Adderall than with phentermine. There are also differences in how often you can refill your prescription.

Controlled substances are categorized based on their dependency and misuse risk. They range from Schedule 1 (highest risk) to 5 (lowest risk). Adderall is a Schedule 2 controlled substance, while phentermine is Schedule 4.

As a Schedule 2 medication, Adderall is more likely to be misused, such as taking more than prescribed. It’s also possible to develop dependence. This means you may experience withdrawal symptoms if you suddenly stop taking it. To limit these risks, Adderall prescriptions can’t be refilled. You’ll need a new prescription each time.

Phentermine is a controlled substance, but it has a lower risk of dependency and misuse. And unlike Adderall, phentermine prescriptions often allow for limited refills.

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Written by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Austin Ulrich, PharmD, BCACP

​​Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. Ulrich’s experience includes direct patient care in hospital and community pharmacies.

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