What Is Phentermine Hydrochloride (HCl)?

Phentermine has been used consistently for medical weight management since it was first approved in 1959. Phentermine is indicated for short term use (generally interpreted as up to 12 weeks) for patients with a BMI* of 30 or more (obese) or 27 or more (overweight) with at least one weight-related condition such as controlled high blood pressure, diabetes, or high cholesterol and should be used in combination with regular exercise and a reduced-calorie diet.

Phentermine is in the class of drugs called “anorectics”, also known as appetite suppressants. The exact mechanism(s) for this suppressant effect is/are unknown, although phentermine is thought to act by increasing the number of various neurotransmitters (norephinephrine, serotonin, dopamine and possibly others) in the spaces between nerve cells in the brain. When these chemicals are increased, the feeling of hunger is minimized.

Recent FDA Actions

In the last five years, the Food and Drug Administration (FDA) has approved five new prescription medicines to help adults manage their weight in combination with diet, exercise, and behavior modification. These medicines include Qsymia® (phentermine and topiramate extended-release) capsules CIV, Belviq® (lorcaserin HCl) CIV, Contrave® (naltrexone HCl and bupropion HCl) extended-release tablets and Saxenda® (liraglutide) injection. Despite the new entrants, phentermine continues to be the most commonly prescribed medicine for weight loss in the United States. Over 7 million prescriptions are written for phentermine yearly by a wide range of healthcare professionals (HCPs), including obesity medicine specialists, family practitioners, endocrinologists, internists and cardiologists.

The fifth and most recent approval (September 2016) in the battle against the disease of obesity is Lomaira™ (phentermine hydrochloride USP) 8 mg tablets CIV, a low-dose formulation of phentermine that can be used up to three times a day before meals. Unlike current dosage forms of phentermine HCl [Adipex-P® (phentermine hydrochloride USP) CIV and generic phentermine 15 mg, 30 mg, and 37.5 mg] that are dosed in the morning before or shortly after breakfast, Lomaira can be dosed up to three times a day to target eating patterns throughout the day.

Personalized Treatment

Now phentermine has more flexibility in dosing, and healthcare professionals and patients can work together to personalize a comprehensive weight-loss treatment plan so that patients can take the dose they need, when they need it. Dosage can be individualized to obtain an adequate response with the lowest effective dose.


Patients should not take phentermine if they have a history of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure or uncontrolled high blood pressure); are taking or have taken a monoamine oxidase inhibitor drug (MAOI) within the past 14 days; have overactive thyroid, glaucoma (increased pressure in the eyes), agitation or a history of drug abuse; are pregnant, nursing, or allergic to sympathomimetic amines.

Generic Phentermine

KVK Tech is the leading manufacturer of phentermine for the American public and produces the most commonly prescribed 37.5 mg tablet of phentermine HCl. Generic phentermine HCl is prescribed in doses ranging from 15 to 37.5 mg and should be taken once a day before or within a few hours of breakfast. Lomaira is now the only strength of phentermine HCl that is FDA-approved to be used up to three times a day before meals. All KVK products are manufactured, packaged, and distributed by KVK in Newtown, Pennsylvania, U.S.A.


*Body Mass Index (BMI) measures the amount of fat in the body based on height and weight. BMI is measured in kg/m2.

Adidpex-P® is a registered trademark of Teva Pharmaceuticals USA, Inc. Belviq® is a registered trademark of Arena Pharmaceuticals GmbH. Contrave® is a registered trademark of Orexigen Therapeutics, Inc. Saxenda® is a registered tradedmark of Novo Nordisk, Inc.