Phentermine Vs. Saxenda: Drug Comparison

Phentermine is the active ingredient in brand-name medications including Adipex-P^®. The information below is about brand name Adipex-P. According to the FDA, “Generic medicines use the same active ingredients as brand-name medicines and work the same way, so they have the same risks and benefits as the brand-name medicines.”

Adipex-P (phentermine hydrochloride) is a prescription medication used as a short-term adjunct to weight loss in patients with obesity. It works as an appetite suppressant by stimulating the central nervous system, which increases heart rate and blood pressure while reducing hunger. Adipex-P is typically prescribed alongside a reduced-calorie diet and exercise regimen to enhance weight loss efforts. Common side effects include increased heart rate, dry mouth, insomnia, and nervousness. It is important to note that Adipex-P is intended for short-term use due to the potential for dependence and other adverse effects​.

Saxenda^® (liraglutide) is an injectable medication used for chronic weight management in adults with obesity or overweight with at least one weight-related condition, such as hypertension, type 2 diabetes, or high cholesterol. It works by mimicking the hormone glucagon-like peptide-1 (GLP-1), which helps regulate appetite and food intake, leading to reduced caloric consumption and weight loss. Administered once daily, Saxenda is used in conjunction with a reduced-calorie diet and increased physical activity. Common side effects include nausea, diarrhea, and constipation, and it should be used with caution in patients with a history of pancreatitis​.

Sympathomimetic amine anorectic

Glucagon-like peptide-1 (GLP-1) receptor agonist

Adipex-P (phentermine hydrochloride) is indicated:

• As a short-term adjunct (a few weeks) in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m², or greater than or equal to 27 kg/m² in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia)

Saxenda (liraglutide) is indicated:

• As an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in:

  • Adult patients with an initial body mass index (BMI) of:

    • 30 kg/m² or greater (obese), or

    • 27 kg/m² or greater (overweight) in the presence of at least one weight-related comorbid condition (e.g., hypertension, type 2 diabetes mellitus, or dyslipidemia)

  • Pediatric patients aged 12 years and older with:

    • Body weight above 60 kg and

An initial BMI corresponding to 30 kg/m² for adults (obese) by international cut-offs

• Typically taken orally once daily

• Comes in 37.5 mg tablets

• Typically taken as an injection once daily

• Comes in single-patient-use pens that deliver 0.6 mg, 1.2 mg, 1.8 mg, 2.4 mg, or 3 mg per injection

Adverse events have been reported in the following systems:

• Cardiovascular

• Central nervous system

• Gastrointestinal

• Allergic

• Endocrine

Most common adverse reactions, reported in greater than or equal to 5% are:

• Nausea

• Diarrhea

• Constipation

• Vomiting

• Injection site reactions

• Headache

• Low blood sugar

• Indigestion

• Fatigue

• Dizziness

• Abdominal pain

• Increased lipase

• Upper abdominal pain

• Fever

• Inflammation of the digestive system

• History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension)

• During or within 14 days following the administration of monoamine oxidase inhibitors

• Hyperthyroidism

• Glaucoma

• Agitated states

• History of drug abuse

• Pregnancy

• Nursing

• Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines

• Drug interactions: Monoamine oxidase inhibitors, alcohol, insulin and oral hypoglycemics, adrenergic neuron blocking drugs

• Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2

• Hypersensitivity to liraglutide or any excipients in Saxenda

• Pregnancy

• Drug interactions: Saxenda delays gastric emptying. May impact absorption of concomitantly administered oral medications

• Coadministration with other drugs for weight loss is not recommended

• Rare cases of primary pulmonary hypertension have been reported

• Rare cases of serious regurgitant cardiac valvular disease have been reported

• Tolerance to the anorectic effect usually develops within a few weeks

• Adipex-P may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle

• Risk of abuse and dependence

• Concomitant alcohol use may result in an adverse drug reaction

• Use caution in patients with even mild high blood pressure

• A reduction in dose of insulin or oral hypoglycemic medication may be required in some patients

• Breastfeeding: Discontinue drug or nursing taking into consideration importance of drug to mother

• Thyroid C-cell tumors

• Acute pancreatitis

• Acute gallbladder disease

• Low blood sugar: Can occur in adults when Saxenda is used with an insulin secretagogue (e.g., a sulfonylurea) or insulin

• Heart rate increase

• Renal impairment

• Hypersensitivity reactions

• Suicidal behavior and ideation

WARNING: RISK OF THYROID C-CELL TUMORS

Liraglutide causes thyroid C-cell tumors at clinically relevant exposures in both genders of rats and mice. It is unknown whether Saxenda causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, as the human relevance of liraglutide-induced rodent thyroid C-cell tumors has not been determined.

Saxenda is contraindicated in patients with a personal or family history of MTC or in patients with multiple endocrine neoplasia syndrome type 2 (MEN 2). Counsel patients regarding the potential risk of MTC and the symptoms of thyroid tumors.

*This information is from the label for brand name Adipex-P^®. See the Full Prescribing Information for more complete information. Phentermine, the active ingredient in Adipex-P, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient phentermine.

*This information is from the label for brand name Saxenda^®. See the Full Prescribing Information for more complete information. Liraglutide, the active ingredient in Saxenda, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient liraglutide.