Prescription phentermine has been around for a long time. And when we say a long time, we mean it. The U.S. Food and Drug Administration (FDA) approved the drug in 1959 (whoa!) for the short-term treatment (just a few weeks) of obesity in adults. And it’s the most common, widely prescribed obesity drug in the United States today.
Phentermine may also ring a bell for some of us because of fen-phen, the once-popular 1990s drug combination of phentermine with either fenfluramine or dexfenfluramine. The combo, touted as a weight-loss miracle drug, was sold as a quick-fix diet pill. And although it was effective for weight loss, and each drug had been approved separately by the FDA, the “fens” were withdrawn from shelves after studies found that the fen-phen combination caused life-threatening side effects. It turned out that as many as one in three patients developed significant heart valve problems. (Side note: the FDA never approved the drugs to be used together.) So, the idea of taking phentermine may raise a few internal alarm bells.
However, phentermine, commonly known by its brand name Adipex-P®, is currently prescribed by itself, also known as monotherapy, or in combination with topiramate under the brand name Qsymia® as a weight-loss drug. Patients prescribed phentermine for weight loss must have a body mass index (BMI) of 30 or greater or a BMI of 27 or greater and at least one weight-related condition like high blood pressure (hypertension), diabetes, or high cholesterol.
Moreover, phentermine is a sympathomimetic amine, and part of a drug class called anorectics. It’s a central nervous system (CNS) stimulant that suppresses your appetite. Phentermine may help reduce your food cravings as an appetite suppressant and increase your metabolic rate so you burn body fat. It’s also chemically related to amphetamine and is a schedule IVcontrolled substance because of the potential risk for addiction.
Because phentermine is a controlled substance with a risk of abuse and dependence, those with a history of substance abuse disorder can’t take it at all. So, although it’s been widely successful for weight loss, you may want a phentermine alternative. It also comes with a host of potential side effects, like increased heart rate, hypertension, restlessness, agitation, dry mouth, headache, and insomnia, that may make you a bit hesitant about trying the popular obesity drug.
So, if you’re wondering, "what’s a good substitute for phentermine," you’ve come to the right
You have many options when considering phentermine alternatives, so choosing can be difficult. Here are five of the best alternatives to phentermine.
Wegovy is a brand name for the drug semaglutide. Wegovy is a once-weekly prescription injectable med and was FDA-approved in June 2021 as a weight-loss treatment for adults with a BMI of 30 or greater or a BMI of 27 or greater with at least one weight-related condition. Unlike phentermine, semaglutide is approved for the long-term treatment of overweight and obesity.
Manufactured by Danish pharmaceutical company Novo Nordisk, Wegovy has shown significant weight loss results in many clinical studies. For example, in a 68-week double-blind trial published in The New England Journal of Medicine in2021 that included almost 2,000 patients (and funded by Novo Nordisk), participants who received a once-weekly 2.4 mg dose of semaglutide lost an average of 14.9% of their body weight compared to the placebo group’s 2.4%.
And, in contrast to some of the most dangerous side effects of phentermine, during the clinical trial, those who received the semaglutide showed improvement in risk factors of cardiovascular events like heart attack and stroke.
Semaglutide is part of the glucagon-like peptide 1 receptor agonist (GLP-1) drug class. GLP-1s work by mimicking the GLP-1 incretin hormone your body already makes that controls appetite and hunger. It also helps to manage blood sugar levels in patients by supporting the pancreas in making enough insulin after you eat.
Wegovy also works to slow digestion, aka stomach emptying, to make you feel full longer. Typically the slow stomach emptying reduces your calorie intake and suppresses appetite. Still, because of this, it can cause some oral pills you may be taking to not be absorbed into your system., Be sure to tell your health care provider about other meds you’re on so they can ensure they’re effective.
Some common semaglutide side effects include nausea, diarrhea, vomiting, constipation, stomach (abdomen) pain, headache, tiredness (fatigue), upset stomach, dizziness, feeling bloated, belching, gas, stomach flu, and heartburn.
Tirzepatide is the active ingredient in the drug Mounjaro. Another once-a-week injectable med, Mounjaro, is currently only FDA approved to treat type 2 diabetes. It’s prescribed in combination with lifestyle changes like a healthy diet and increased physical activity to help manage blood glucose levels. But, many health care professionals prescribe Mounjaro for weight loss off-label, and there’s a very good reason why.
Mounjaro's manufacturer, Eli Lilly, announced in an April 2022 press release that in a 72-week phase 3 clinical trial, participants lost up to 22.5% of their body weight. The press release said that of those on the 15 mg dose, “63% of people taking tirzepatide achieved at least 20% body weight reductions.”
This kind of weight-loss success is unparalleled except in surgical intervention like bariatric surgery. That’s exactly why in October 2022, the FDA gave Lilly the go-ahead for Mounjaro to be studied for the treatment of obesity and gave the drug a Fast Track designation. This Fast Track means the med review and approval process for tirzepatide will be expedited to “fulfill an unmet medical need,” said the FDA.
Mounjaro belongs to a drug class all its own called a glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide 1 (GLP-1) receptor agonist. Yes, we mentioned GLP-1s above, but tirzepatide not only works by mimicking the GLP-1 hormone but also the body’s natural GIP hormone, so it’s working in two ways to help control blood-sugar levels, giving it a leg up as a diabetes drug, and eventually one for obesity.
Common side effects of Mounjaro include nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, and stomach (abdominal) pain. Lilly also notes in the prescribing information that it can decrease the efficacy of oral birth control pills, so if you’re sexually active and on an oral contraceptive, chat with your health care provider about birth control alternatives while taking Mounjaro.
Saxenda, or liraglutide, is an injectable med that’s also part of the GLP-1 drug class and is manufactured by Novo Nordisk. Although it hasn’t been around as long as phentermine, in today's terms of obesity meds, it’s been around for a while. In fact, it was approved by the FDA in 2014 for treating obesity in adults with a BMI of 30 or greater or 27 or greater with a weight-related condition like high blood pressure, type 2 diabetes mellitus, and high cholesterol. On top of that, in 2020, liraglutide was FDA-approved for children 12 years and older with obesity and who weigh more than 132 pounds to be used in combination with diet and exercise.
Saxenda is also meant for long-term weight management and is approved for continued use. A review of five randomized, placebo-controlled trials published in 2017 in the journal Obesity Science & Practice found that when patients took liraglutide together with the recommended reduced-calorie diet and increased physical activity, liraglutide consistently resulted in about a 9- to 13-pound weight loss, with more patients achieving at least 5%-10% weight loss compared with the placebo groups.
Saxenda may be a great alternative to phentermine. Just note the common side effects of liraglutide are nausea, diarrhea, constipation, vomiting, injection site reaction, low blood sugar (hypoglycemia), headache, tiredness (fatigue), dizziness, stomach pain, and change in enzyme (lipase) levels in your blood.
Because Saxenda is a GLP-1, it also works by delaying stomach emptying. The same warning also goes here about mentioning to your doctor any oral meds you may be on to ensure they maintain their efficacy in your body.
Dulaglutide is the active ingredient in the type 2 diabetes drug, Trulicity. FDA approved in 2014 for diabetes management and then in 2020 to reduce negative cardiovascular events like heart attack, stroke, and even death in adults with type 2 diabetes with established cardiovascular disease or multiple cardiovascular risk factors. Although Trulicity is approved for diabetes, doctors can prescribe Trulicity for weight loss off-label in adults with overweight or obesity.
Trulicity is manufactured by Eli Lilly and is a part of the GLP-1 family. It's been a successful weight loss treatment for patients; in a 52-week study published in 2021 in Diabetes Care of almost 2,000 patients whose type 2 diabetes was not adequately controlled by the diabetes drug metformin were given once-weekly injections of dulaglutide at doses of 1.5 mg, 3 mg, or 4.5 mg. At 36 weeks, patients treated with the 4.5 mg dose of dulaglutide lost about 10 pounds compared to those on the 1.5 mg dose, who lost about 6 pounds.
Like other GLP-1s, Trulicity has a few common side effects including nausea, diarrhea, vomiting, abdominal pain, decreased appetite, indigestion, and fatigue.
If you’re wary of phentermine diet pills, dulaglutide may be a viable phentermine substitute for you to try.
Important note: GLP-1s come with the same black box warning because of the risk of thyroid C-cell tumors. In testing, these tumors developed in mice, so be advised of this serious risk factor before taking any GLP-1 prescription drug. Do not use them if you or a family member has a history of MTC or if you have multiple endocrine neoplasia syndrome type 2 (MEN 2).
Orlistat is the generic name for the brand name Alli®. And you’ve most likely heard or seen this medication because it's the only FDA-approved over-the-counter (OTC) weight loss aid for adults 18 and older with a BMI of 25 or more. It’s made by GlaxoSmithKline (GSK), and Alli belongs to a class of drugs called lipase inhibitors. It blocks the intestines from absorbing about 25 percent of the fat you eat. This means that the fats that aren’t absorbed leave your body through bowel movements.
Unlike the GLP-1 meds we’ve covered above, Alli is an oral pill that’s typically taken within an hour of a meal up to three times a day. Orlistat was originally FDA-approved for prescription only in 1999; in 2007, Alli was approved for OTC use for weight loss.
Even more, Alli is currently approved for two years of continuous use; some of the most common side effects include stomach pain, upset stomach, oily anal discharge, gas, oily stools, increased bowel movements, headaches, back pain (which may be a symptom of kidney stones), and menstrual change.
So, if you want to steer clear of the weekly injections and stick to the oral pill route, Alli may be the answer to what you can take for weight loss instead of phentermine.
If you want to hit your weight-loss goals with something other than a prescription weight-loss medication, you may want to reconsider. Of course, many phentermine alternative supplements claim they curb your sugar cravings, trigger fat loss, or come with a 60-day money-back guarantee.But many of those are false claims. In all actuality, weight-loss supplements that boast they burn fat, suppress appetite, and boost metabolism may do more harm than good. It’s easy to fall prey to some of the marketing ads out there, so be on the alert and consult with your doctor before you try anything new.
Be cautious of over-the-counter diet pills that include thermogenic ingredients like cayenne pepper, green tea extract, green coffee, vitamin B6, and guarana. Even though they may sound innocent, extensive studies on the safety and effectiveness of natural supplements for weight loss prove otherwise.
A review published in 2019 in Critical Reviews in Food Science and Nutrition studied literature ranging from 2006 to 2016 and found that “contrary to popular belief, results of this review suggest that the use of natural supplements for weight loss are unlikely to contribute to meaningful weight loss and in some cases may contribute to harm.”
Even more, the FDA is there for a reason—to keep us healthy and safe, as well as to vet medications to ensure they’re high-quality before they’re prescribed. While the FDA does regulate supplements, they don’t need to pass through the FDA’s strict drug guidelines before being mass-marketed as OTC phentermine alternatives. In fact, in 1994, the Dietary Supplement Health and Education Act (DSHEA) was passed, giving supplement companies and distributors the power over the safety of their own products. So supplements may not be as safe as you think because they haven’t had to undergo the rigorous governmental process that drugs do.
Some other natural ingredients to be on the lookout for—and speak to your health care professional about before trying—are L-theanine, glucomannan, L-tyrosine, chromium picolinate, garcinia cambogia, phenylalanine, and rhodiola rosea. Be sure to ask about name-brand weight-loss pills that say they increase energy levels and have fat-burning abilities as natural phentermine alternatives like PhenGold, PhenQ, Phen24, PrimeShred, Leanbean®, and Trimtone before you try them.
Again, we’re not trying to harp, but your safety and care are crucial. So it's important to talk to a health care professional before beginning any new supplement, especially those that profess to be natural appetite suppressants or over-the-counter phentermine alternatives.
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Access to GLP-1s prescriptions is now available as part of Found's weight-loss program. While GLP-1s are effective for weight loss, they are not clinically appropriate for everyone. Eligibility for a GLP-1 is based on a thorough evaluation of medical history, eating behavior, lab work, and insurance coverage. If a GLP-1 is not appropriate or affordable for you, Found providers can help determine if another effective medication is.