Contrave Vs. Phentermine: Drug Comparison

Contrave^® (naltrexone hydrochloride and bupropion hydrochloride) is a prescription medication used for weight management in adults, combining two active ingredients: naltrexone, which affects the brain's reward system, and bupropion, which influences appetite and cravings. It works by targeting the hypothalamus to reduce hunger and the mesolimbic reward system (a pathway in the brain that plays a key role in regulating feelings of pleasure, motivation, and reinforcement) to curb food cravings. Contrave is FDA-approved for chronic weight management. Common side effects include nausea, constipation, headache, and insomnia, while drug interactions can occur with MAO inhibitors, opioid pain medications, and drugs that lower the seizure threshold. Contrave carries a boxed warning for an increased risk of suicidal thoughts and behaviors, particularly in young adults, due to its bupropion component.

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​.

Naltrexone: opioid antagonist

Bupropion: aminoketone antidepressant

Sympathomimetic amine anorectic

Contrave (naltrexone hydrochloride and bupropion hydrochloride) is indicated:

• As an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adults with an initial body mass index (BMI) of:

  • 30 kg/m² or greater (obese)

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

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)

• Typically taken orally twice daily

• Comes as 8 mg/90 mg extended-release tablets

• Typically taken orally once daily

• Comes in 37.5 mg tablets

Most common adverse reactions (greater than or equal to 5%):

• Nausea

• Constipation

• Headache

• Vomiting

• Dizziness

• Insomnia

• Dry mouth

• Diarrhea

Adverse events have been reported in the following systems:

• Cardiovascular

• Central nervous system

• Gastrointestinal

• Allergic

• Endocrine

• Uncontrolled hypertension

• Seizure disorders, anorexia nervosa or bulimia, or undergoing abrupt discontinuation of alcohol, benzodiazepines, barbiturates, and antiepileptic drugs

• Use of other bupropion-containing products

• Chronic opioid use

• During or within 14 days of taking monoamine oxidase inhibitors (MAOI)

• Known allergy to any of the ingredients in Contrave

• Drug interactions: MAOIs, antidepressants (e.g., selective serotonin reuptake inhibitors and many tricyclics), antipsychotics (e.g., haloperidol, risperidone, and thioridazine), beta-blockers (e.g., metoprolol), type 1C antiarrhythmics (e.g., propafenone and flecainide), digoxin, CYP2B6 inhibitors (e.g., ticlopidine or clopidogrel), CYP2B6 inducers (e.g., ritonavir, lopinavir, efavirenz, carbamazepine, phenobarbital, and phenytoin), drugs that lower seizure threshold, dopaminergic drugs (levodopa and amantadine)

• 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

• Suicidal behavior and ideation

• Neuropsychiatric adverse events during smoking cessation

• Risk of seizure may be minimized by adhering to the recommended dosing schedule and avoiding coadministration with high-fat meal

• Increase in blood pressure and heart rate

• Liver toxicity

• Angle-closure glaucoma

• Use of antidiabetic medications: Weight loss may cause hypoglycemia

• Pregnancy: Weight loss during pregnancy may cause fetal harm. Discontinue when a pregnancy is recognized

• 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

WARNING: SUICIDAL THOUGHTS AND BEHAVIORS

Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants for major depressive disorder and other psychiatric disorders. Monitor for worsening and emergence of suicidal thoughts and behaviors.

Contrave has not been studied in pediatric patients.

*This information is from the label for brand name Contrave^®. See the Full Prescribing Information for more complete information. Naltrexone and bupropion, the active ingredients in Contrave, may also be the active ingredients in other medications, and this information may not be accurate for all medications that include the active ingredients naltrexone and bupropion.

*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.