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Phentermine

This article examines the use of phentermine, a medication approved for short-term weight loss, in various clinical trials. Researchers are investigating phentermine’s effectiveness, safety, and potential for long-term use in treating obesity, often in combination with other drugs or interventions. The trials aim to better understand how phentermine affects weight loss, eating behaviors, and obesity-related health issues.

Table of Contents

What is Phentermine?

Phentermine is a medication primarily used for weight loss in overweight and obese individuals. It’s known by several brand names, including Adipex-P, Lomaira, and Ionamin[1]. Phentermine has been approved by the US Food and Drug Administration (FDA) for weight management since 1959[2]. It’s classified as an anti-obesity medication and is often prescribed as part of a comprehensive weight loss program that includes diet and exercise.

Uses of Phentermine

Phentermine is primarily used for:

  • Weight Loss: It’s prescribed to help overweight or obese individuals lose weight[3].
  • Chronic Weight Management: Some studies have explored its use in long-term weight management[3].
  • Obesity-related Conditions: It may be used in patients with weight-related health issues like hypertension (high blood pressure), dyslipidemia (abnormal blood fats), or sleep apnea[3].

How Phentermine Works

Phentermine belongs to a class of drugs called anorectics or appetite suppressants. It works by:

  • Stimulating the release of certain brain chemicals that help reduce appetite[1].
  • Increasing the feeling of fullness, which can help you eat less[1].

Dosage and Administration

The dosage of phentermine can vary depending on the specific formulation and the patient’s needs. Common dosages include:

  • 15-37.5 mg taken orally once daily[4].
  • Some formulations, like Lomaira, come in 8 mg tablets that can be taken up to three times a day[2].

It’s typically recommended to take phentermine in the morning to help reduce potential insomnia[3]. Always follow your doctor’s instructions regarding dosage and timing.

Phentermine Combinations

Phentermine is sometimes used in combination with other medications for enhanced weight loss effects:

  • Phentermine-Topiramate (Qsymia): This combination has been studied for its effects on weight loss and blood pressure[5].
  • Phentermine-Lorcaserin: This combination has been studied for its potential in weight loss[3].
  • Phentermine-Orlistat: This combination has been studied for its effects on weight loss and vascular function in overweight patients with back pain[6].

Effectiveness

Studies have shown that phentermine can be effective for weight loss when used as part of a comprehensive weight management program. Some key findings include:

  • Phentermine, when combined with lifestyle interventions, can lead to significant weight loss over 12 weeks[3].
  • In some studies, phentermine has been shown to help patients achieve 5% or more weight loss[3].
  • Combination therapies, such as phentermine-topiramate, have shown promising results in long-term weight management[5].

Side Effects and Safety

Like all medications, phentermine can cause side effects. Common side effects may include:

  • Headache, dizziness, nausea, fatigue, dry mouth, diarrhea, vomiting, insomnia, and anxiety[3].
  • Increased blood pressure and heart rate[6].

It’s important to note that phentermine is a controlled substance due to its potential for abuse and dependence[2]. Always use it as prescribed by your doctor.

Long-term Use

Traditionally, phentermine has been approved for short-term use (up to 12 weeks). However, recent studies are exploring its potential for longer-term use:

  • The LEAP (Long-term Effectiveness of the Anti-obesity medication Phentermine) trial is studying the effects of phentermine use for up to 2 years[2].
  • Some experts argue that since obesity is a chronic disease, long-term use of anti-obesity medications like phentermine may be beneficial[2].

Use in Special Populations

Phentermine has been studied in various populations:

  • Bariatric Surgery Patients: Some studies have looked at using phentermine before bariatric surgery to reduce liver fat and make the surgery easier[7].
  • Patients with Back Pain: The combination of phentermine and orlistat has been studied in overweight patients with back pain[6].
  • Patients with Gastric Bands: Research has explored whether phentermine can enhance weight loss in patients who have had gastric band surgery[8].
Aspect Details
Primary Uses Short-term weight management, appetite suppression
Combination Therapies Studied with lorcaserin, topiramate, and B12
Duration of Studies Ranging from 12 weeks to 2 years
Key Outcomes Measured Weight loss, changes in BMI, blood pressure, eating behavior
Special Populations Obese adults, bariatric surgery patients
Safety Monitoring Cardiovascular effects, dependence potential, adverse events
Novel Applications Pre-surgical weight loss, long-term obesity management
Dosage Forms Immediate-release and modified-release formulations

FAQ

  • What is phentermine and how does it work for weight loss? Phentermine is an appetite-suppressing medication approved for short-term weight management. It works by stimulating the release of certain brain chemicals that help reduce hunger and increase feelings of fullness, making it easier for people to eat less and lose weight.
  • Are there any clinical trials studying the long-term use of phentermine? Yes, the LEAP (Long-term Effectiveness of the Anti-obesity medication Phentermine) trial is investigating the effects of phentermine use for up to 2 years. This study aims to understand the long-term impacts on weight, blood pressure, and other health outcomes when phentermine is used beyond the currently approved 12-week period.
  • Is phentermine being studied in combination with other weight loss treatments? Several trials are exploring phentermine in combination with other treatments. For example, one study is investigating the combination of phentermine with lorcaserin, while another is looking at phentermine combined with topiramate. These combination approaches aim to enhance weight loss effectiveness.
  • What are some potential side effects of phentermine being monitored in clinical trials? Clinical trials are monitoring various potential side effects of phentermine, including changes in blood pressure, heart rate, and cardiac function. Some studies are also assessing the risk of dependence on the medication and tracking any adverse events related to cardiovascular health.
  • How is phentermine being studied in relation to bariatric surgery? Some clinical trials are investigating the use of phentermine before or after bariatric surgery. For instance, one study is examining whether phentermine can help reduce intrahepatic fat and adipose tissue in patients preparing for bariatric surgery, while another is looking at its potential to augment weight loss following gastric band surgery.

Ongoing Clinical Trials on Phentermine

  • Study Comparing Amitriptyline, Flunarizine, Topiramate, and Propranolol for Preventing Migraines in Primary Care Patients

    Recruiting

    1 1 1 1
    Investigated drugs:
    Spain

Glossary

  • Phentermine: A medication approved for short-term use in weight management that works by suppressing appetite.
  • BMI (Body Mass Index): A measure used to assess body fat based on height and weight, often used to categorize individuals as underweight, normal weight, overweight, or obese.
  • Lorcaserin: A weight loss medication that works by activating serotonin receptors in the brain to help people feel full with smaller amounts of food.
  • Topiramate: An anticonvulsant medication that, when combined with phentermine, is used for weight loss in some formulations.
  • Bariatric Surgery: Surgical procedures performed on the stomach or intestines to induce weight loss in severely obese individuals.
  • Intrahepatic Fat: Fat stored within the liver cells, which can be associated with obesity and metabolic disorders.
  • Pharmacokinetics: The study of how a drug is absorbed, distributed, metabolized, and eliminated by the body.
  • Placebo: An inactive substance or treatment used in clinical trials as a control to compare against the effects of the drug being studied.
  • Adverse Event: Any unfavorable and unintended sign, symptom, or disease temporarily associated with the use of a medical treatment or procedure.
  • Resting Metabolic Rate (RMR): The number of calories your body burns while at rest, which can be affected by weight loss interventions.

References

  1. https://clinicaltrials.gov/study/NCT01886937
  2. https://clinicaltrials.gov/study/NCT05176626
  3. https://clinicaltrials.gov/study/NCT01987427
  4. https://clinicaltrials.gov/study/NCT03374956
  5. https://clinicaltrials.gov/study/NCT05215418
  6. https://clinicaltrials.gov/study/NCT03675191
  7. https://clinicaltrials.gov/study/NCT03849729
  8. https://clinicaltrials.gov/study/NCT00771654