By Dr. Asnat Raziel, bariatric surgeon specializing in obesity treatment, metabolic health and healthy longevity; Director of the Multidisciplinary Center for Obesity Treatment, Assia Medical, Assuta Ramat HaChayal, Tel Aviv
Razin (phentermine): the veteran pill that still works
Razin (phentermine) is one of the longest-established pills for treating obesity, and it remains an important tool even in the era of injections. Its active ingredient is phentermine, and it reduces hunger by acting on the appetite centers in the brain. That makes it especially suitable for people who struggle with strong hunger throughout the day.
It is also a convenient, readily available pill that does not act on the satiety hormones. However, it is suitable only after a medical evaluation, because it affects heart rate and blood pressure.
What is Razin and how does it work?
Razin, the Israeli brand name for phentermine, belongs to the family of mild stimulants. It raises levels of norepinephrine in the brain and, to a lesser extent, dopamine and serotonin. As a result, hunger decreases and portion control improves.
Unlike drugs from the GLP-1 family, Razin does not slow stomach emptying, so nausea and a feeling of fullness are rare. On the other hand, it can cause a rapid heart rate, dry mouth and trouble falling asleep.
Most people feel the effect on appetite within the first few days. Many people describe a quieter mind around food, which makes it easier to stick with a structured eating plan from the start.
How much weight can you lose with Razin (phentermine)?
In a controlled study published in the journal Obesity, a 28-week trial tested phentermine at a dose of 15 mg. Of the participants in this group, 46.2% lost at least 5% of their body weight. In contrast, participants in the placebo group lost an average of only 1.7% of their weight.
What’s more, a large study based on medical records followed 13,972 phentermine users. About 8 in 10 were women, and the average BMI was 38. The researchers found that people who stayed on treatment for a long time lost more weight than those who stopped after three months.
For example, 144 users took the drug continuously for more than a year. Over two years of follow-up, they maintained a loss of more than 7% of their starting weight. In addition, those who lost at least 3% of their weight in the first three months generally went on to succeed later as well.
Can Razin be used long-term?
In the past, Israeli rules limited treatment with Razin to three months. However, in November 2024 the Israeli Ministry of Health clarified that treatment duration is not part of the product’s approved indication. In other words, a doctor may prescribe Razin long-term, as long as the patient has regular follow-up.
Moreover, the large follow-up study found no increase in the risk of cardiovascular events or death with long-term use, up to three years from the start of treatment. In total, researchers recorded a serious event in 41 users (0.3%), and none of them were in the long-term user group. In addition, systolic blood pressure in long-term users actually fell over two years of follow-up.
How to take it and dosing
Razin comes in capsules containing 15 mg of phentermine. Take one capsule in the morning, before breakfast or shortly after. Avoid taking it in the evening, because the drug can disrupt sleep.
Your doctor will decide how long to continue treatment based on your response, blood pressure and heart rate. It’s a good idea to measure your blood pressure at home during the first few weeks and bring the readings to your follow-up visit.
Side effects of Razin (phentermine)
Most patients adapt to treatment well. However, there are some side effects worth knowing about:
- Rapid heart rate or palpitations
- Increased blood pressure
- Dry mouth and an unpleasant taste
- Trouble falling asleep, especially if you take it late in the day
- Irritability, restlessness or headache
- Constipation or diarrhea
Very rarely, doctors have reported pulmonary hypertension. Anyone who develops new shortness of breath, chest pain, fainting or leg swelling should stop the drug and see a doctor.
Who should not take Razin?
According to the product information, patients should not take phentermine in the following situations:
- Cardiovascular disease, including coronary artery disease, stroke, arrhythmias and heart failure
- Uncontrolled high blood pressure
- Overactive thyroid
- Glaucoma
- Severe anxiety or agitation
- A history of substance misuse
- Pregnancy and breastfeeding
- Taking MAO inhibitors, or within 14 days of stopping them
Combining Razin (phentermine) with other medications
Today, many doctors combine Razin (phentermine) with advanced treatments such as Mounjaro or semaglutide. The combination is mainly suitable for patients with persistent hunger or weight loss that is too slow. Doctors can also combine it with Xenical, which acts in the digestive tract.
However, any combination requires personalized adjustment and close follow-up. You can read more in my articles on combined obesity treatment and on personalizing weight-loss medications.
A holistic approach: a window of opportunity for change
The drug works best as part of a comprehensive program. First, a diet tailored to the patient’s characteristics. Second, gradually increasing physical activity, along with balanced sleep and stress management. It’s also important to address emotional eating when it is present.
Razin creates a “window of opportunity”: hunger subsides, and the patient can build new habits. That way, even if the patient stops the drug in the future, those habits will help maintain the result.
Frequently asked questions about Razin
How long does it take to see an effect?
Most people notice the reduction in appetite within the first few days. However, weight loss develops gradually, so doctors assess it after about three months.
Can Razin be taken for more than three months?
Yes. The Israeli Ministry of Health has clarified that treatment duration is not part of the approved indication, so your doctor can continue it at their discretion, with follow-up.
What happens when you stop?
Appetite returns gradually, so regaining weight is common. That’s why you and your doctor should plan the stopping phase, or the switch to another treatment, in advance.
The bottom line
Razin (phentermine) is a long-established, accessible and effective treatment that fits well even in the era of the new medications. It reduces hunger quickly, and with appropriate medical follow-up, patients can use it long-term. It’s worth discussing with a doctor who is familiar with the full range of obesity treatment options.
The information in this article is general and does not replace personalized medical advice.
Dr. Acosta of the Mayo Clinic talks about the types of obesity and how doctors tailor treatment to each:
References
Razin: Israeli Ministry of Health clarification on treatment duration (in Hebrew)
Using phentermine for weight loss more than 3 months seems safe and effective
