Taking Phentermine And Adderall Together

In our latest question and answer, the pharmacist discusses the use of phentermine with Adderall.


Can you find PubMed articles or guidelines supporting that phentermine and Adderall should not be prescribed together? I've tried but can't seem to find anything. Looking for documentation to send to the prescribers in my area that expect me to dispense both at the same time.

Asked by Jocelyn On Apr 11, 2019

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Apr 11, 2019
Can Adderall Be Used With Phentermine With Blue Capsule Background


It's unlikely that you will find any scientific articles evaluating the combined use of Adderall (mixed amphetamine salts) and phentermine since they are essentially the same type of drug (sympathomimetics).

In fact, the prescribing information for phentermine (and drugs that contain phentermine, like Qsymia) discusses the amphetamine-like nature of the drug:[1]

Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and dll-amphetamine).

Combined Use

Combining sympathomimetic drugs is generally not recommended due to the increased risk of certain side effects, including:[2][3]

  • Increased Blood Pressure
  • Agitation
  • Irritability
  • Increased heart rate

There are no medical guidelines that recommend the combined use of phentermine and Adderall (amphetamine salts). Additionally, there is no drug product approved by the FDA that combines the two.

There was an investigational drug undergoing clinical trials in the 1960s, Bionamin, that combined phentermine and amphetamine salts but it was never approved due to the lack of efficacy and concern over side effects.[4][5]

Side Effect Concern

In terms of anti-obesity drugs structurally similar to phentermine, they are all associated with serious side effects. These side effects include primary pulmonary hypertension (PPH) and cardiac valvulopathy.[6]

Phentermine appears to be the safest amphetamine-like drug indicated to treat obesity and whether or not there is a risk of the serious side effects listed above (when used at recommended doses) is disputed.[7]

Nevertheless, a slew of drugs similar to phentermine that were once available on the market have all been withdrawn due to their association with those negative side effects (sibutramine, fenfluramine etc...)[8]

Using Two Stimulants?

Going back to potentially combining phentermine and Adderall, their use together isn't recommended due to their potentially additive effects since they work the same way (by causing the release of several neurotransmitters, including norepinephrine, dopamine and to a lesser extent, serotonin).

Guidelines for ADHD and for the treatment of obesity don't recommend combined use of stimulants (i.e. sympathomimetics).[9][10]

If combined pharmacologic therapy is needed, it generally is only with a stimulant and a non-stimulant.

For example, for ADHD, a combination of methylphenidate and guanfacine has been studied. For obesity, phentermine and topiramate together has been studied).[11][12]

Certainly, if phentermine and amphetamine are used together, routine monitoring of blood pressure and emotional state should be done at the very least.

Final Words

Based on your question, you seem to be a pharmacist and are being asked to dispense phentermine and Adderall at the same time, which is certainly a cause for concern.

Be sure to use your professional judgment on a case-by-case basis and speak with the prescriber to make sure they fully consider the risks and benefits of this therapy. Always document your conversations!  Additionally, be sure the patient knows the risks.


Combined use of phentermine and Adderall (mixed amphetamine salts) is generally not recommended due to their similar mechanism of action and risk of additive side effects.

  1. ^ Apidex-P Prescribing Information
  2. ^ Phentermine--a "weighty" or a dangerous substance? PubMed
  3. ^ Anti-Obesity Drugs: A Review about Their Effects and Safety. PubMed
  4. ^ Comparison of phentermine-amphetamine resin complex with sustained-release dextroamphetamine and placebo in the treatment of exogenous obesity. PubMed
  5. ^ Competitive problems in the drug industry. Google Books
  6. ^ Pulmonary Hypertension Associated with Use of Phentermine. PubMed
  7. ^ RE: Pulmonary Hypertension Associated with Use of Phentermine? PubMed
  8. ^ FDA Drug Safety Communication: FDA Recommends Against the Continued Use of Meridia (sibutramine)? FDA
  9. ^ Diagnosis and Management of Attention-Deficit/Hyperactivity Disorder in Adult. American Family Physician
  11. ^ Combined Stimulant and Guanfacine Administration in Attention-Deficit/Hyperactivity Disorder: A Controlled, Comparative Study PubMed
  12. ^ Clinical utility of phentermine/topiramate (Qsymia™) combination for the treatment of obesity. PubMed

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Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of PharmacistAnswers.com. He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Brian.Staiger@PharmacistAnswers.com Office: 716-389-3076

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