Terfamex: Phentermine Weight Loss Pills

Terfamex is a Mexican brand of phentermine weight loss pills. Available in both capsule and orally disintegrating tablet (ODT) form, this medication helps suppress appetite and boost energy so that patients can lose weight more quickly and easily. It is only sold under a doctor’s prescription and should not be used for more than 12 weeks at a time. Terfamex is available in Mexico, Venezuela, Peru, Colombia, Panama, and Argentina.


Too busy for the full read? Here’s what you need to know:

  • Terfamex is a Mexican brand of phentermine weight loss pills that suppress appetite and boost energy.
  • Terfamex is only available with a doctor’s prescription.
  • This medication is available in capsule and orally disintegrating tablet form and in three different doses (15mg, 30mg, and 37.5mg).
  • Terfamex should not be used for more than 12 weeks at a time.
  • It is suitable for people with a BMI greater than 30 or those with a BMI greater than 27 coupled with a weight-related condition like type 2 diabetes or high blood pressure.
  • Terfamex can have side effects, including dry mouth, insomnia, constipation, headache, rapid heart rate, mood changes, and changes in sex drive.

What is Terfamex?

woman holding an apple that is wrapped in a measuring tape
Terfamex is a popular brand of phentermine that is used to help obese patients lose weight

Terfamex is a Mexican brand of phentermine weight loss pills that are sold in Latin America. It’s a branded preparation of the popular prescription appetite suppressant, phentermine hydrochloride (phentermine HCL).

This medication helps overweight patients eat less and move more to lose weight faster by suppressing their appetite and giving them an extra boost of energy.

Given its strength and addictive potential, the compound is classified as a class IV controlled substance. As a result, Terfamex (phentermine) is a short-term medication and is only available under a doctor’s prescription.

Who Can Take Terfamex?

This medication is an option for people with a body mass index (BMI) greater than 30, who are considered medically obese. It is also available for overweight patients with a BMI greater than 27 if the individual also struggles with a weight-related condition like type 2 diabetes or high blood pressure.
However, a patient’s level of obesity is not the only factor to consider.

It is also important to asses why a patient is overweight, as well as their current health status, other medications, and medical history.

Terfamex (phentermine) should not be used in the presence of some medical conditions or in combination with some medications ( 1 ).

Learn more here: Phentermine Contraindications


Terfamex is currently available in two different presentations and three different doses. At your prescribing appointment, your doctor will work with you to determine which dose and presentation are correct for you.


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Terfamex 15mg

Fifteen milligrams is the lowest dose of this medication. It is the only dose that is sold in both capsule and ODT form.

Terfamex 15 mg box

Terfamex 15 mg pills can be taken one or two times per day, depending on the doctor’s orders.

People who struggle with nighttime cravings or binging sometimes prefer to take two smaller doses of phentermine throughout the day so that the medication’s effects last longer. However, if you struggle with insomnia, this may not be the best option.

Terfamex 30 mg

Terfamex 30 mg is the highest dose of Terfamex available in capsule form.

Terfamex 30 mg box

It should only be taken once a day. Most patients take this pill before breakfast (first thing in the morning) with a full glass of water.

Terfamex 37.5 mg

In Latin America, 37.5 mg is the maximum daily dose of phentermine. Terfamex offers this dose as an ODT. 

Terfamex OD box

Terfamex OD should only be taken once a day, preferably in the early morning.

However, since it dissolves on your tongue, Terfamex 37.5 can be taken with or without water. ODTs are a good option for people that have trouble swallowing pills, but they tend to cost more than traditional capsules or tablets ( 2 , 3 ).


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How To Take Terfamex

Since this is a prescription medicine, your doctor and pharmacist will give you clear directions about how to take Terfamex. Follow these instructions.

Always take this medication EXACTLY as prescribed.

Given the medication’s addictive potential, as well as its progressive loss of efficacy, Terfamex should only be taken for 12 weeks at a time. The United States FDA only approved phentermine for this short course of treatment, and research has not assessed the safety of taking the medication for longer periods of time ( 1 ).

If you and your doctor feel that you need more than three months of treatment to reach a healthy weight, your prescribing physician may choose to prescribe you multiple rounds of phentermine punctuated by regular breaks.  

When to Take Terfamex

Your doctor will talk to you about specific dosing instructions to accommodate your individual schedule, but phentermine is usually taken:

  • First thing in the morning (before breakfast), or
  • 1-2 hours after breakfast.

Given the simulant properties of phentermine HCL, do not take Terfamex within 8 hours of bedtime. This should be easy if you are only taking one pill per day, but if you take 15 mg twice per day, take your second dose relatively early in the afternoon so that you can sleep at night.

Side Effects

Woman holding her head, suffering from a headache
Terfamex side effects include dry mouth, headache, and constipation

Phentermine is a phenomenally effective weight loss medication, but it can also cause some serious side effects.

While most patients experience only mild reactions – such as dry mouth, headache, or insomnia – others are forced to deal with more severe effects.

Severe Side Effects

A severe reaction to Terfamex may be evidenced by one or more of the following symptoms:

  • Chest pain
  • Trouble breathing
  • Fainting
  • Swelling of feet or lower legs
  • Difficulty in carrying-out day to day activities

 Go to the hospital or seek immediate medical attention if you experience any of the above symptoms while taking Terfamex (phentermine).

Common Side Effects

While it is important to remain aware of serious potential side effects, most patients only experience mild reactions to this medication. Common side effects of phentermine include: 

  • Dry mouth (xerostomia)
  • Trouble sleeping (insomnia)
  • Constipation
  • Headache
  • Dizziness
  • Rapid heart rate
  • Mood changes (e.g. “phen rage”)
  • Changes in sex drive

Read more here: Phentermine Side Effects

Contact your doctor if you have ANY Terfamex side effect that bothers you, doesn’t go away, or seems to be getting worse.

Other Considerations

assorted packets of pills
Tell your doctor about all other medications and supplements before starting Terfamex diet pills

While taking Terfamex, or before pursuing a prescription for this weight loss medication, consider the following factors:

Terfamex and Alcohol

Phentermine is an “upper” while alcohol is a “downer.”

The combination of these two substances increases patients’ risk of cardiovascular and other side effects, like dizziness, racing heart, and high blood pressure.

Since both phentermine and alcohol affect each person differently, it’s risky and potentially dangerous to combine the two substances. Do NOT drink alcohol while taking Terfamex ( 4 ).

Terfamex and Pregnancy

You should not take Terfamex if you are pregnant or trying to conceive. In the US, phentermine is classified as pregnancy category X.

Professionals are not sure whether phentermine passes into the breast milk, so you should also avoid this medication if you are nursing or pumping milk ( 1 , 5 ).

Given these recommendations, many female patients ask specifically about Terfamex and birth control.

While many people use birth control successfully alongside phentermine, some sources indicate that taking a birth control pill with phentermine can increase the risk of thrombosis. As a result, it’s important to talk to your prescribing doctor, pharmacist, and gynecologist about Terfamex and birth control before starting treatment.

Terfamex and Other Medications

Terfamex interacts with many medications and supplements. Always ask your doctor and pharmacist before combining any new medication or supplement with phentermine.

It is especially important to tell your prescribing doctor if you take, or have recently taken any:

  • Antidepressant medications, including monoamine oxidase inhibitors (MAOIs) or selective serotonin reuptake inhibitors (SSRIs)
  • Blood pressure medications, such as guanadrel o guanethidine ( 3 ).

However, these are not the only pills that interact with phentermine. For this reason, it’s important to tell your doctor and pharmacist about all recent medications (prescription and OTC) and supplements before starting phentermine.

Read more here: Medications and Other Phentermine Contraindications

Where to Buy Terfamex

If you are interested in taking phentermine for weight loss, speak to your doctor about a prescription. He or she will evaluate the appropriateness of this medication in your specific case and then assess whether this medication is right for you.

After obtaining a valid prescription, you can buy Terfamex at most major pharmacies in:

  • Mexico
  • Venezuela
  • Peru
  • Colombia
  • Panama
  • Argentina

Read more here: How to Get a Prescription for Phentermine

Terfamex Without a Prescription

Terfamex is NOT available without a prescription.

The main ingredient (phentermine HCL) is a controlled substance, so distribution and sale of these prescription weight loss pills is tightly controlled. It is illegal and dangerous to purchase this medication without a prescription.


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Price of Terfamex

Terfamex costs about 180-460 Mexican pesos (or 9-25 US dollars) for 30 pills, which typically equates to a one-month supply of medication.
The table below shows the average price of Terfamex at major Mexican pharmacies:

CapsulesAverage Cost of 30 Pills
15 mg$179 (MXN)-$260 (MXN)
$9 (USD)-$14 (USD)
30 mg$298 MXN (MXN)-$425 (MXN)
$15 (USD)-$22 (USD)
ODTAverage Cost of 30 Pills
15 mg$327 (MXN)-$367 (MXN)
$17 (USD)-$19 (USD)
37.5 mg$399 MXN (MXN)-$464 (MXN)
$21 (USD)-$25 (USD)

NOTE: These prices are only estimates and do not represent any type of guarantee or coupon. Last updated May 2023 ( 6 , 7 , 8, , 9 ).

Terfamex vs. Other Weight Loss Pills

Interested in prescription weight loss medications, but not sure if Terfamex is right for you? Here’s a comparison of this brand of phentermine to other medications and supplements on the market.

Terfamex vs. Acxion

Terfamex and Acxion are two brands of phentermine weight loss pills available in Mexico.

box of IFA acxion (phentermine)

Both pills contain the same active ingredient and come in a variety of doses, but the presentations are different.

Both brands have capsules, but Terfamex also comes in an ODT, while Acxion offers extended-release tablets.

The two brands cost about the same.

Terfamex vs. Orlistat

Terfamex and Orlistat are both prescription weight-loss medications, but they contain different active ingredients.

While Terfamex contains phentermine HCL as its active ingredient, Orlistat is the generic name (and active ingredient) of weight loss medications like Xenical and Alli.

Orlistat box

Unlike phentermine which acts as a stimulant, Orlistat decreases fat absorption to help patients lose weight ( 9 ). It does not affect appetite or energy, so eating proper portions and staying active is left up to you and your willpower while taking Orlistat.

Orlistat is legal in most countries, including many that have banned phentermine. It is sold under various brand names, including Andanza, Lindeza, Redustat, Orlistat MK, Xenical, and Alli.

Terfamex vs. Redotex

Redotex is often called the “Mexican Miracle Diet Drug”, but actual reviews of the prescription-only weight loss medication are very mixed. In fact, Redotex is banned in the USA due to safety concerns.

box of Redotex NF

Unlike Terfamex, which contains phentermine HCL as its active ingredient, Redotex relies on a cocktail of potentially-dangerous stimulant ingredients, including norpseudoephedrine, atropine sulfate, diazepam, aloin, and triiodothyronine.

Talk to your doctor about the benefits and risks of different diet pills before filling your prescription.

Terfamex Reviews

Does Terfamex actually help them lose weight? Are the side effects worth it? Recent reviewers indicate that the pills work well, but often cause a myriad of uncomfortable side effects.

Terfamex has an average user rating of 4.3/5.

Here are some recent Terfamex reviews:

Isabella – Positive Results
Today is my last day taking Terfamex 30mg. I’ve seen a lot of positive results in my body and my health, and I’m happy that I haven’t had side effects like other people I’ve read about. I took Redotex NF before, and even though I lost weight, the side effects were too much.

Maribell – Deception
I tried this medicine because my girlfriends insisted that it was the best thing to lose weight, but it’s not… The side effects are too much. The constipation was the worst, and the headaches were unbearable, and it made my mouth taste bad too. I lost 21 pounds, but that’s not enough, given how miserable I felt.

Nathy – Incredible!
I think this pill is better than the original USA one. I’ve lost 32 pounds so far and still going strong.

Who Makes Terfamex?

Terfamex was developed by KVK-TECH, but it is currently manufactured and distributed by Medix S.A. The two companies reached this agreement in 2017, in an effort to expand KVK-TECH’s business into Central America.

Medix Laboratories logo

Productos Medix S.A. de C.V.
Calzada del Hueso No. 39, Ex Ejido de Santa Ursula Coapa, Deleg. Coyoacán, 04650, México, D.F.
IPPA Code: KEAR-06330022080212/RM2008


Terfamex vs Phentermine – what’s the difference?

Terfamex is a phentermine-based weight loss medication that contains phentermine hydrochloride (phentermine HCL) as its main ingredient. Terfamex is sold in Mexico and Latin America.

Do I need a prescription for Terfamex?

Yes, Terfamex is a prescription medication. It’s important to consult with a doctor before using it, as it can have significant side effects and may not be suitable for everyone. Your doctor is the only person to assess your health condition and determine if Terfamex is right for you.

Where is Terfamex available?

Terfamex is primarily available in Mexico, but it can also be found in other Latin American countries such as Venezuela, Peru, Colombia, Panama, and Argentina.

Can I Buy Terfamex at Amazon?

No, you cannot get Terfamex at Amazon. The medication’s main ingredient (phentermine HCL) is a class IV controlled substance, and it is illegal and dangerous to purchase Terfamex without a prescription.

How long can I use Terfamex?

Terfamex should not be used for more than 12 weeks at a time, as it is intended for short-term use. This is because the effects of the medication tend to decrease over time, and prolonged use can lead to dependency. Always follow your doctor’s specific instructions for use.

  1. Piqueras, C. (2018, June 18). Terfamex (Fentermina), Qué es, Cómo Funciona, Efectos Secundarios!!!
  2. Farmacias San Pablo. (2018). Terfamex.
  3. NDrugs.com. (2018, April 07). Terfamex Overdose, Warnings, Precautions, Missdose.
  4. SDrugs.com. (2017, March 07). Terfamex drug & pharmaceuticals. Terfamex available forms, doses, prices.
  5. Jakubowicz, S., Dr. (2014, June 16). Cómo tomar Terfamex (fentermina) para adelgazar 11 kgs.
  6. Superama en línea. (2018). Terfamex.
  7. Walmart. (2018). Terfamex.
  8. FarmaListo. (2018). Buscar “termafex”.
  9. Pastillas para adelgazar (2016, October 06) Orlistat dosis y contraindicaciones.