Phentermine is a short-term appetite suppressant primarily used to treat patients whose obesity may lead to serious health problems. This medication works by regulating hunger signals in the central nervous system, reducing the desire to eat and decreasing caloric intake. It is usually recommended to be used in conjunction with dietary control, exercise programs, and behavioral therapy to enhance weight loss effects. Its mechanism involves stimulating the sympathetic nervous system to release catecholamines, which suppress appetite.
The efficacy of Phentermine typically becomes evident within a few weeks of starting use, but it is approved only for short-term treatment (usually not exceeding 12 weeks). Long-term use may lead to tolerance or increased side effects; therefore, physicians prescribe it based on the patient’s body mass index (BMI) and health risk assessment. This medication is not suitable for mild weight issues and is only provided as a short-term aid for high-risk patients.
The generic name for Phentermine is "Fenfluramine," with common brand names including Adipex, Lomaira, and Ionamin. Different brands may have dosage adjustments due to formulation types or added ingredients, but the active component remains the same. In Taiwan or Hong Kong, this medication may be available under different commercial names, depending on local drug approval regulations.
Patients should pay attention to the brand name and generic name on the prescription label provided by the doctor, and verify the ingredients listed on the packaging. If allergic to any components, discontinue use immediately and contact a healthcare provider. Combination formulations may contain other weight-loss ingredients; it is important to confirm whether Phentermine is included to avoid duplicate medication use.
Phentermine is classified as an "appetite suppressant" and is a derivative of phenylethylamine. These drugs primarily act on the central nervous system by affecting neurotransmitters such as norepinephrine and dopamine to regulate appetite. Its pharmacological action is similar to amphetamines, but due to its shorter duration of action and lower dependency potential, it is approved for obesity treatment.
This classification requires special attention to addiction risk. Although Phentermine has a lower addictive potential compared to other amphetamines, prolonged or excessive use can still lead to psychological or physiological dependence. Physicians strictly control the usage cycle and regularly evaluate risk-benefit ratios during prescription.
Phentermine is mainly used for patients with a BMI (Body Mass Index) ≥30 who are severely obese, or BMI ≥27 with obesity-related conditions such as hypertension or diabetes. It is suitable for short-term (usually not exceeding 12 weeks) weight loss assistance, combined with daily calorie control and regular exercise. For some patients, short-term use can help establish healthy lifestyle habits and gradually reduce dependence on medication.
It is not recommended for patients with mild obesity or those seeking purely cosmetic weight loss. The U.S. Food and Drug Administration (FDA) approves its use only for medically necessary weight reduction, with regular monitoring of weight changes and side effects. Physicians will assess suitability based on age, health status, and medical history.
Mild side effects include dry mouth, insomnia, dizziness, nausea, and anxiety, which usually occur early in treatment and diminish over time. Some patients may experience palpitations, increased blood pressure, or arrhythmias, requiring regular vital sign monitoring. Gastrointestinal discomfort such as diarrhea or constipation may also occur; taking medication with meals can help reduce gastrointestinal irritation.
Serious side effects requiring immediate medical attention:
If any of these symptoms occur, stop medication immediately and notify healthcare personnel.
Contraindications include:
This medication has a risk of addiction; caution is advised for individuals with a history of substance abuse. Pregnant or breastfeeding women should not use it, as it may harm the fetus or inhibit milk production.
The FDA has issued a "black box warning" emphasizing its addiction potential and cardiovascular side effects. Regular monitoring of blood pressure and electrocardiograms is necessary during use, especially for patients with a history of heart disease. Elderly patients over 65 or those with liver or kidney impairment should have dosage adjustments to prevent accumulation and toxicity.
Phentermine should not be combined with monoamine oxidase inhibitors (MAOIs); at least 14 days should pass after stopping MAOIs before starting Phentermine. Combining with other stimulants such as Adderall or Ritalin can increase cardiac workload and may induce arrhythmias. When used with antihypertensive medications, it may reduce their effectiveness, requiring dose adjustments.
Avoid combining with caffeine-containing drinks or supplements (such as Ephedra), as this may cause a significant increase in blood pressure. Certain antidepressants like SSRIs may increase the risk of serotonin syndrome, requiring medical evaluation and adjustment of medication plans. Before using traditional Chinese medicines or herbal supplements, inform your doctor, especially if containing Ma Huang or ephedra components.
Starting doses typically range from 3.75 mg to 15 mg, taken on an empty stomach in the morning. The physician may adjust the dose up to a maximum of 30 mg based on efficacy, with close monitoring for side effects. Tablets should not be chewed or broken; swallow whole to ensure proper release. If a dose is missed, take it as soon as remembered, but if close to the next dose, skip the missed dose to avoid doubling.
The treatment duration usually does not exceed 12 weeks. Before continuing, re-evaluate weight changes and health indicators. Doses should be carefully adjusted for children, adolescents, and the elderly; use in patients under 18 is only in extreme cases. The medication may affect sleep quality, so it is recommended to take it between 8-10 am to reduce insomnia risk.
If a dose is missed and less than 2 hours remain before the next scheduled dose, take it immediately and continue with the regular schedule. If more than 4 hours have passed since the missed dose, skip it and resume normal dosing; do not double the dose to compensate. For multiple missed doses or prolonged discontinuation, record the missed instances and consult your doctor for assessment.
Set daily reminders for medication, such as alarms or mobile apps. If medication is temporarily stopped due to side effects, contact your doctor immediately rather than adjusting the dose yourself. Store medication out of reach of children and do not share with others.
Overdose can cause severe symptoms including hypertensive crisis, ventricular fibrillation, hyperthermia, and seizures. If overdose is suspected, seek emergency medical help immediately and bring the medication container for reference. Symptoms may include body temperature up to 40°C, pulse over 120 bpm, or altered consciousness. Overdose can be life-threatening and should not be waited out.
Emergency measures include stopping the medication immediately and removing any remaining pills. Medical personnel may use beta-blockers to lower blood pressure or activated charcoal to prevent gastrointestinal absorption. Long-term abuse may lead to cardiac hypertrophy or psychological dependence, requiring addiction treatment and psychological counseling. Patients should store medication properly to prevent accidental ingestion by teenagers or others.
Do I need to follow a specific diet plan while taking Fenfluramine?
It is recommended to follow a low-calorie, high-fiber diet plan during Fenfluramine use. While this medication suppresses appetite, it alone may not achieve long-term weight loss; it should be combined with a balanced diet and moderate exercise. Doctors usually suggest creating a personalized diet plan and regularly monitoring eating habits.
How can I alleviate dizziness or insomnia caused by Fenfluramine?
Dizziness or insomnia are common side effects. Taking the medication in the morning may reduce nighttime effects. If symptoms persist, your doctor may adjust the dose or recommend short-term sleep aids such as magnesium or melatonin. If symptoms are severe, stop medication immediately and seek medical attention, avoiding increasing the dose on your own.
What are the risks of using Fenfluramine with antidepressants?
Using with selective serotonin reuptake inhibitors (SSRIs) or tricyclic antidepressants may increase the risk of serotonin syndrome, characterized by high fever, muscle spasms, or altered consciousness. Inform your doctor of all medications you are taking, especially psychiatric drugs, before use.
Will weight rebound quickly after stopping short-term use?
If diet and exercise habits are not maintained after stopping medication, about 50-70% of patients may regain their original weight within 6-12 months. It is advisable to develop healthy habits during medication use and continue monitoring afterward. Your doctor may recommend behavioral therapy or long-term low-dose medication.
Can patients with hypertension use Fenfluramine?
This drug may raise blood pressure; therefore, patients with hypertension or cardiovascular disease should use it cautiously. Blood pressure should be measured before starting, and monitored at least twice weekly during treatment. If blood pressure exceeds 160/100 mmHg, the doctor may suspend use and evaluate alternative options.
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