Comparing Phentermine 37.5 vs Adipex

Comparing Phentermine 37.5 and Adipex is an extremely common thing to do on search engines such as Google.  However, what many people don’t realize is that there isn’t actually all that much that differentiates the two medications.

That is, there really isn’t a Phentermine 37.5 vs Adipex for comparing.  Instead, while there are some things that are very slightly different between the two of them, for many people, they may as well be identical.  If you’ve been prescribed either one of these obesity drugs, or if you’re considering asking your doctor about them, then read on.  This will help you to better understand what they’re all about and why people tend to try to compare them. 

That way, you’ll be prepared for an informed, productive discussion with your physician.  You’ll know that you’re not really looking at Phentermine 37.5 vs Adipex in terms of two vastly different drugs as much as you’re just comparing the minor differences to fine tune your final decision about what’s best for you.

What are Adipex and Phentermine 37.5?

Comparing Phentermine 37.5 vs Adipex

The fast answer with respect to what Adipex and Phentermine 37.5 mg are is that they are the same and yet slightly different prescription obesity drugs.  That made things worse, didn’t it?  Fair enough.  Consider it a jumping off point while you’re comparing them. 

A Basic Comparison of Adipex vs Phentermine 37.5

Basically speaking, they are the same because they are both drugs prescribed by doctors.  They are prescribed to people suffering from obesity and who need assistance in adopting the new healthy lifestyle habits their doctors recommend for dropping the pounds.  They are composed of the same active ingredient medication.

On the other hand, looking at it from an Adipex vs Phentermine 37.7 comparison standpoint, there are indeed some differences.  The main difference is that the former is a brand name version of this drug while the latter is a generic form.  Moreover, their inactive ingredients – that is, the substances that don’t actually have an impact on the obesity you’re treating, but that comprise the pill itself, such as binders or the outer capsule – may not be identical. 

Furthermore, while there are some exceptions, the generic is usually less expensive than the brand name and is more likely to be covered by a health insurance policy.

Not much of a difference, right?  Let’s look a little deeper.  Nothing changes the fact that they’re essentially an identical medication, but it doesn’t mean that taking them both will provide the same exact experience.

How Are Brand Name and Generic Phentermine the Same?

Both of these drugs are based on the active ingredient phentermine hydrochloride.  This is the only active ingredient in both medications regardless of whether they are in capsule or tablet form.  That drug was the first diet pill to receive F.D.A. approval for action based on suppressing the appetite.

As such, it became – and remains – the most commonly prescribed obesity drug in the United States.  It is more commonly prescribed as generic Phentermine 37.5 mg than Adipex, but that is typically due to the reduced cost of the medication as opposed to some reason involving its action.

Phentermine hydrochloride is believed to work on appetite suppression by stimulating the central nervous system.  This includes the nerves as well as the brain.  More specifically, it alters the hypothalamus, the appetite center of the brain, through several chemical changes. 

Comparing the Use of Adipex and Phentermine 37.5

When either one of those medications is prescribed, it’s important to follow the directions to the letter.  If you have received a prescription and are unsure about how to use your obesity drug properly, be sure to ask the prescribing doctor or your pharmacist for further guidance.

Typically speaking, a prescription for Adipex or Phentermine 37.5 won’t require only swallowing a pill.  Instead, it will also include dietary changes as well as other potential lifestyle changes such as boosting physical activity, focusing on stress reduction, making a higher priority of getting regular restful sleep, and more.

There is really no comparing Adipex and Phentermine 37.5 in this way as they both require the same type of change.  Dietary changes typically mean that the patient will need to restrict caloric intake to within a certain range.  That range will likely change as weight loss continues.  They will also involve a fitness appropriate exercise strategy to keep up physical activity levels.

Neither drug is meant to cause weight loss on its own.  Instead, they help to suppress the appetite so it’s easier to cut back on calories.  Beyond that, they also boost energy levels to make it easier to maintain motivation levels.  This way, it’s easier to stay on track with the new eating strategy and regular workouts.  Beyond that, extra energy can also go a long way to help power through workouts and burn the most possible fat and calories.


If you are prescribed Adipex or Phentermine 37.5, make sure to tell your doctor or pharmacist about any other medical conditions you may have, as well as medications you are taking (prescription or non-prescription) or dietary supplements you use or plan to use at the same time as your obesity drug.

The reason is that these tablets and capsules are not appropriate for everyone, even if you suffer from obesity.  They are known to contradict with over 130 other medications – many of them quite common.  They can also cause problems with several types of medical conditions. 

This doesn’t necessarily mean that you won’t be able to use Adipex or Phentermine 37.5, but it will mean that your doctor will need to do a comparison of the benefits versus drawbacks and may alter the prescription for this drug or one of the other medications you’re using in order to ensure it will be safe for you. 

It’s also important to note that even if you take these pills properly, there is still a risk of side effects.  Most are mild and temporary, but there is a chance of more severe side effects.  Side effects for Adipex and Phentermine 37.5 include (but aren’t limited to):

  • Nausea
  • Vomiting
  • Irritability
  • Diarrhea
  • Insomnia and other sleep struggles
  • Dry mouth
  • Dizziness
  • Constipation
  • Blood pressure changes
  • Mental/mood changes
  • A fast/pounding/irregular heartbeat
  • Agitation/uncontrolled anger/nervousness/hallucinations
  • Uncontrolled muscle movements
  • Change in sexual interest/ability
  • Severe headache
  • Seizure
  • Slurred speech
  • Weakness on one side of the body
  • Blurred vision or other vision changes
  • Dangerous lung or heart problems

Do the Differences Matter?

After reading (or skimming, let’s be real) everything so far, you may wonder if there are any factors at all for comparing Adipex vs Phentermine 37.5 that would make one stand out above the other.  Is there really a difference between the two that would mean one is more appropriate for you than the other? 

At the ground level, the answer would be “no”.  Essentially, if you get one medication, you’ll enjoy the same benefits and drawbacks as you would if you were prescribed the other.  That said, among the differences between the two, you might find that one is just slightly more appropriate for you even though it has nothing to do with the way it benefits your efforts to overcome obesity.

The first has to do with allergies.  Since the only way the pills themselves truly differ is in their inactive ingredients, then if you are allergic to the inactive ingredients in one but not the other, then the choice for one over the other would be very easy.  It’s important to note that an allergy to the non-active ingredients in these pills is extremely rare, but it is worth pointing out when comparing Adipex vs. Phentermine 37.5 in this context. 

The second is cost.  Assuming you don’t have an allergy to the inactive ingredients in either of these obesity drugs, most people tend to lean toward using the generic Phentermine 37.5 pill.  The reason is that it doesn’t cost as much as Adipex.  Moreover, many drug plans will only cover generic versions of a medication (where they exist), so people with health insurance coverage including a drug plan will typically opt for the generic for that reason.