Mounjaro Vs Phentermine: Which Is Best For Weight Loss

Mounjaro Vs Phentermine is a comparison article of these two drugs although both of these drugs have not been investigated in a head-to-head comparison trial. Mounjaro is a once-weekly injectable diabetes medicine and its FDA approval as a weight loss drug is still pending. Phentermine, on the other hand, is a drug that suppresses appetite and boosts metabolism.

Phentermine is available in the markets under the brand names Adipex-P and Suprenza. It was approved by the FDA for the short-term treatment of weight loss in addition to diet and exercise.

However, the FDA now recommends using Phentermine for weight loss only in combination with a topiramate combo drug that is available in the markets under the brand name Qsymia.

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The Basic Differences Between Mounjaro and Phentermine:

Mounjaro is a newly-approved first-in-its-class dual incretin mimetic drug. It is also called Twincretin as it enhances the action of both GLP-1 and GIP in the body.

Mounjaro is used as a once-a-week subcutaneous injection. It is initiated in a dose of 2.5 mg once weekly for four weeks and then titrated every four weeks by 2.5 mg up to a maximum dose of 15 mg per week.

It is approved only for use in Type 2 Diabetic individuals and is considered the most potent diabetes medicine. Currently, its approval as a weight loss drug by the FDA is pending. The manufacturer, Eli Lilly hopes that Mounjaro will get approved by the end of 2023.

Phentermine is an orally disintegrating tablet that gets dissolved readily when kept over the tongue. It is available in three different strengths 15, 30, and 37.5 mg as Phentermine Hydrochloride (equivalent to 12, 24, and 30 mg of phentermine).

It is a stimulant and appetite suppressant drug, approved for weight loss in combination with Topiramate as Qsymia.

Phentermine Vs Mounjaro: Basics
	Phentermine	Mounjaro
Class	Sympathomimetic	Dual GLP-1 and GIP analog
Drug/Brand	Adipex-P, Suprenza	Tirzepatide
Manufacturer	Teva, Akrimax	Eli Lilly
Uses (Approved Indication)	Weight Loss (with Topiramate)	Diabetes Type 2

One major difference between Mounjaro and Phentermine (Adipex-P) is that Mounjaro is a prescription-only medicine while Phentermine (Adipex-P) is available over the counter (OTC medicine).

Phentermine is sold @ 39 USD on Amazon while one monthly cost of Mounjaro is around USD 1100 without insurance and USD 35 with Insurance.

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How effective is Mounjaro Vs Phentermine for Weight Loss?

Tirzepatide (Mounjaro) and phentermine have not been studied in a head-to-head comparison. The weight loss effects presented here are indirect comparisons vs placebo.

In a study performed in a Mexican obese otherwise healthy population, Phentermine in a dose of 15 mg and 30 mg was evaluated for 3 to 6 months.

The weight loss effects ranged from 4 to 8 kgs as presented here in the table below:

Weight loss [Ref]	Phentermine 15 mg	Phentermine 30 mg
Weight lost at 3 months	-4.5 kg	-5.8 kg
Weight lost at 6 months	-6.9 kg	-8.4 kg

The weight loss effect of Mounjaro was also evaluated in obese individuals. The study included more than 2500 participants who were obese or overweight with at least one obesity-related medical condition like hypertension, dyslipidemia, sleep apnea, etc excluding diabetes [Ref])

Mounjaro significantly lowered body weight ranging from 15 to 21% at different doses. The picture below summarizes the weight loss effects of Mounjaro vs Placebo.

percentage weight loss with mounjaro — **Percentage weight loss with Mounjaro**

Mounjaro Vs Phentermine: Weight loss difference vs Placebo:

Mounjaro is considered more potent than Phentermine. In fact, Phentermine is not approved as a weight loss drug. It is only approved for weight loss with Topiramate as Qsymia.

However, the table below is given for the sake of comparison to determine the difference in weight loss between Mounjaro and Phentermine:

Mounjaro Vs Phentermine: Weight Loss Difference Vs Placebo
Efficacy	Mounjaro	Phentermine
Weight Loss	5 mg: -5.3 kg 10 mg: -6 kg 15 mg: -6.8 kg	-5.3 kg [Ref]
Percent weight loss	5 mg: -11.9 % 10 mg: -16.4 % 15 mg: -17.8 % (at 72 weeks [Ref])	4.4% (at 28 weeks [Ref])

The weight loss effects of Mounjaro 5 mg and Phentermine are probably comparable. However, as the dose of Mounjaro is increased, it is associated with significantly greater weight loss than Phentermine.

From the table above, it may be concluded that Mounjaro is associated with 7% to 13% greater weight loss than Phentermine.

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Mounjaro Vs Phentermine Side Effects and Drug Interactions:

Mounjaro (Tirzepatide) is way more safe than Phentermine. Apart from the gastrointestinal side effects associated with Mounjaro, it is not associated with significant side effects.

On the other hand, Phentermine is a stimulant drug. It has got an addictive potential. Like other stimulant drugs, it may be misused by people to achieve euphoria and become overactive. In addition, it is also associated with withdrawal symptoms.

However, the big difference in terms of side effects is that Phentermine may cause angina, hypertension, and worsen heart failure. On the other hand, Mounjaro may protect your heart.

Here is a table summarizing the side effects of Mounjaro Vs Phentermine:

Mounjaro Vs Phentermine Side Effects and Contraindications
Side effects	Mounjaro	Phentermine
Contraindications	Allergic reactions MEN II syndrome Medullary thyroid carcinoma	Cardiac diseases (angina, heart failure, stroke, hypertension, arrhythmias) Hyperthyroidism Glaucoma Agitation Drug dependence in the past Allergic reactions Pregnancy and Breastfeeding Use with MAO Inhibitors
Side effects of Mounjaro and Phentermine	Hypoglycemia Pancreatitis Renal failure Nausea Vomiting Diarrhea Abdominal pain Constipation Gallstones Amylase elevation Lipase elevation Injection-site reactions Fatigue Palpitations	Pulmonary hypertension Drug Tolerance Abuse and dependence Withdrawal effects Palpitations Hypertension Overstimulated, agitation, and euphoria Psychosis Headaches Dry mouth constipation or Diarrhea Altered taste Urticaria Loss of libido Impotence

There are certain drugs that should be avoided when you are using Mounjaro or Phentermine. The table below summarizes these drug interactions:

Mounjaro Vs Phentermine Drug Interactions
Drug Interactions	Mounjaro	Phentermine
Avoid	Bexarotene Gatifloxacin	MAO Inhibitors
Monitor when given in combination	Insulin Oral Contraceptives Oral antidiabetic medications Warfarin Corticosteroids Diuretics Fenofibrate Salmeterol Antidepressants (MAO inhibitors)	Alcohol Insulin Oral hypoglycemic drugs Sympathomimetics Adrenergic blockers

It is important to note that since Mounjaro is a drug used for diabetes, most drug interactions are related to anti-diabetics.

Furthermore, Mounjaro delays gastric emptying and may impair the absorption of some important medicines like levothyroxine and warfarin.

Phentermine is a stimulant drug and if given within 14 days of using an MAO inhibitor, it may result in a hypertensive crisis. In addition, the patient may need to adjust his/ her blood pressure medications when starting Phentermine for weight loss.

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