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Phentermine-Prozac (Phen-Pro) for losing weight: An update with Michael Anchors (1998)
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Wednesday, September 10, 2003 3:51 pm Email this article
This is an update to the interview with Michael Anchors, M.D., Ph.D. about the use of Phen-Pro, the combination of phentermine and Prozac or certain other SSRIs.
This interview was first published in Obesity Research Update, August 1997, Volume 2 Number 8.
Dr. Anchors can be reached as follows:
Michael Anchors, MD, PhD
16220 Frederick Rd Ste 210
Gaithersburg, MD 20877
(301) 990-6061
(301) 990-6064 Fax
.(JavaScript must be enabled to view this email address)
Hobbs: What is the drug combination that you are using for weight loss?
Anchors: Phentermine and Prozac (Phen-Prozac).
Hobbs: When did you start using Phen-Prozac?
Anchors: March 1995.
Hobbs: How many patients have you treated with Phen-Prozac?
Anchors: About 620.
Hobbs: Do you ever use phentermine alone?
Anchors: No. Phentermine alone isn’t very effective. Patients lost a little weight at first, but gained it back even when they kept taking it. Phen-Prozac works much better.
Hobbs: Did you ever prescribe Fen-Phen?
Anchors: No. I considered fenfluramine to have unnecessary risks such as primary pulmonary hypertension (PPH) and possible heart valve damage. In fact, in the book (page 59) I predicted that we would see cases of heart valve damage in some people taking fenfluramine.
Hobbs: Does Prozac increase the risk of PPH?
Anchors: No. Eli Lilly, the company that manufactures Prozac, has received only 8 reports of PPH in people taking Prozac out of 19 million users worldwide. This is even fewer cases than would be expected in the general population. The reason is that Prozac does not force the release of serotonin like fenfluramine does. It only blocks the reuptake. Prozac is also more than 98% protein-bound in the blood, whereas fenfluramine is much less protein-bound and so is more available to cause trouble.
Hobbs: Will you comment on the letter from Bostwick and Brown (1996) regarding a toxic reaction from combining phentermine and Prozac.
(Reference: Bostwick JM, Brown TM. A toxic reaction from combining fluoxetine and phentermine [letter]. Journal of Clinical Psychopharmacology, 1996 Apr, 16(2):189-90.)
Anchors: First of all the phentermine was started at a dose of 30 mg, which should not be done. And second, the “toxic reaction” occurred 8 days after the Prozac was stopped.
Hobbs: How does Phen-Prozac compare in to Fen-Phen as far as efficacy?
Anchors: I believe they are equally effective.
Hobbs: How does Phen-Prozac compare to Redux as far as efficacy?
Anchors: I think that Phen-Prozac or Fen-Phen, for that matter, is more effective than Redux. I’ve treated a number of patients who failed to lose weight with Redux, but were successful with Phen-Prozac.
Hobbs: How do they compare as far as side effects?
Anchors: Phen-Prozac generally causes fewer side effects than Fen-Phen. And Phen-Prozac is better tolerated than either phentermine or Prozac alone.
Hobbs: Have you had any problems with anxiety using Phen-Prozac?
Anchors: Rarely. It’s probably because I start with a small dose of phentermine and gradually increase it and I only use 10 mg of Prozac.
Hobbs: If Fen-Phen didn’t work for someone, is it likely that Phen-Prozac might work?
Anchors: I have some patients who did not lose weight with Fen-Phen, but did lose weight with Phen-Prozac. I think it is certainly worth a try.
Hobbs: What percentage of your Phen-Prozac patients have lost weight?
Anchors: Most of them. Only 10 out of 620 failed to lose when following the program. A few dozen more failed to lose weight because they didn’t take the medicines as prescribed, ate when they weren’t hungry or didn’t exercise.
Hobbs: How did you decide to use Phen-Prozac rather than Fen-Phen?
Anchors: There were a couple reasons. First, fenfluramine is not covered by most insurance plans, but Prozac is. Second, fenfluramine has a shorter half-life, so it has to be taken two or three times per day, whereas Prozac only has to be taken once per day. Prozac also generally has fewer side effects than fenfluramine.
Hobbs: What is the dose of Phen-Prozac that you use?
Anchors: 30 mg of phentermine plus 10 mg of Prozac. But I always have patients start with only 15 mg of phentermine for the first week or two and then increase it to 30 mg to reduce the initial side effects.
Hobbs: Why do you think it is that only 10 mg of Prozac is necessary when combined with phentermine, whereas using Prozac alone seems to require at least 60 mg?
Anchors: Only 10 mg is needed for weight loss, although a higher dose is needed to treat depression.
Hobbs: Studies indicate that weight loss with Prozac alone only lasts for 6 months or so and then patients return to their previous weight. Have you had any problem with patients regaining a substantial amount of weight using Phen-Prozac?
Anchors: No. I have never seen a patient gain weight on Phen-Prozac.
Hobbs: What do you do when patients reach their target weight?
Anchors: About 25% of patients are able to stop taking the medicines, and the other 75% still need a small dose to maintain their lower weight.
Hobbs: What do you mean by a small dose?
Anchors: Typically, 15 mg of phentermine plus 10 mg of Prozac every other day for some weeks of the month.
Hobbs: Can other serotonin reuptake inhibitors (SSRI) be substituted for Prozac?
Anchors: Yes. Phen-Zoloft, Phen-Trazodone, and Phen-Luvox all seem to work.
Hobbs: How do you decide whether to use Prozac, Zoloft, trazodone or Luvox?
Anchors: If a patient is controlling their depression with one particular SSRI I’ll keep them on that and just add the phentermine. Or if I start a patient on Phen-Prozac and they experience side effects I may switch them to another SSRI.
Hobbs: For example?
Anchors: Zoloft is a good choice when patients are also taking medications for other conditions because it is less likely to interfere with other drugs. Zoloft also loosens the stool which is useful for patients who experience too much constipation from phentermine.
If a patient has problems sleeping trazodone is a good choice. It’s also available as a generic so it’s cheap.
And Luvox is a good choice for patients who experience a decrease in libido from Prozac.
Hobbs: What doses do you use?
Anchors: When I use Phen-Trazodone I have them take the phentermine in the morning and 50 to 100 mg of trazodone at night.
When I use Phen-Luvox I have them take 25 to 50 mg of Luvox.
And with Zoloft I use 25 to 50 mg.
The dose of phentermine is always 30 mg.
Hobbs: Do you ever combine phentermine with 2 SSRIs like Phen-Prozac-Trazodone or Phen-Trazodone-Luvox?
Anchors: Yes. Sometimes I combine low dose Prozac with low dose trazodone in depressed patients, because trazodone helps them sleep.
Hobbs: Have you tried any other combinations like Phen-Tryptophan or Phen-5HTP (5-hydroxytryptophan)?
Anchors: No. I think that tryptophan is capable of causing heart valve disease for the same reason that fenfluramine does.
Hobbs: What criteria do you use for trying a patient on Phen-Prozac?
Anchors: The usual. I’ll try it only if they: 1) have failed to maintain weight loss by diet and exercise; 2) have a body mass index (BMI) greater than 30 or; 3) a BMI of 27 if they have obesity-related health problems. And, of course, they can’t have any contraindications to the medicines.
Hobbs: Are there SSRIs or other antidepressants that don’t work?
Anchors: Yes. Elavil√? (amitriptyline) and Pamelor√? (nortriptyline) don’t work because they stimulate appetite. Paxil√? doesn’t work either. Neither does Wellbutrin√? or Serzone√?.
Hobbs: What other benefits have you found with Phen-Prozac?
Anchors: Many of my patients have said they found it easier to stop smoking or drinking.
I’ve also found that phentermine is an effective treatment for attention deficit disorder (ADD). I discovered this after some of my Phen-Prozac patients told me that could concentrate better. So I tried substituting phentermine for Ritalin in young obese patients with ADD and I found that phentermine worked just as well an Ritalin and they lost weight. Dr. Rothman previously published a paper on using phentermine for ADD.
Rothman RB. Treatment of a 4-year-old boy with ADHD with the dopamine releaser phentermine [letter]. Journal of Clinical Psychiatry, 1996 Jul, 57(7):308-9.)
Anchors: I’ve also found that Phen-Prozac works for obsessive-compulsive disorder (OCD). After taking Phen-Prozac for a while one of my patients confessed that she previously had a compulsion to buy compact discs and had purchased 10,000 of them! After taking Phen-Prozac her compulsion went away and she lost 94 lbs. Other patients have told me that have stopped using their credit cards compulsively.
And, as I mentioned before, Phen-Prozac seem to have an easier time stopping addictive behaviors like smoking, drinking and illicit drugs.
Dr. Michael Anchors on Phen-Prozac (updated in October 2000)
Hobbs: How many patients have you treated with Phen-Prozac?
Anchors: 1058. This is the total of all my patients on “Phen-Pro”, which consists of phentermine plus one of the serotonin reuptake inhibitors (SSRIs). About 70 percent of my patients are on Phen-Prozac, 20 percent of Phen-Zoloft, 10 percent on Phen-Luvox and 10 percent on Phen-Trazodone.
Hobbs: Have you tried Phen-Wellbutrin, Phen-Effexor, Phen-Serzone or Phen-Paxil?
Anchors: Yes, I’ve tried all of these. Phen-Wellbutrin doesn’t work any better than phentermine alone. That is tachyphylaxis develops after 6 weeks. It makes sense that Wellbutrin would not work because it doesn’t work on serotonin. The 3 times I tried it Phen-Serzone was not tolerated. And in all of the patients I tried Phen-Effexor they developed nausea. But now that slow-release Effexor XR has become available, it might be worth a second look. And Phen-Paxil does not work.
Hobbs: How do you decide whether to use Prozac, Zoloft, trazodone or Luvox?
Anchors: If a patient is controlling their depression with one particular SSRI I’ll keep them on that and just add the phentermine. Or if I start a patient on Phen-Prozac and they experience side effects I may switch them to another SSRI.
Hobbs: For example?
Anchors: Zoloft is a good choice when patients are also taking medications for other conditions because it is less likely to interfere with other drugs. Zoloft also loosens the stool which is useful for patients who experience too much constipation from phentermine.
If a patient has problems sleeping trazodone is a good choice. It’s also available as a generic so it’s cheap.
And Luvox is a good choice for patients who experience a decrease in libido from Prozac.
Hobbs: What doses do you use?
Anchors: The same doses that I suggested in Safer Than Phen-Fen, that is 10 or 20 mg of Prozac; 25 or 50 mg of Zoloft; 25 or 50 mg of Luvox; or 25 or 50 mg of Trazodone. Padla’s study showed that higher doses cause less weight loss than lower doses. I’ve confirmed this to be true.
Hobbs: Do you ever combine phentermine with two SSRIs like Phen-Prozac-Trazodone or Phen-Trazodone-Luvox?
Anchors: Yes. Sometimes I combine low dose Prozac with low dose trazodone in depressed patients, because trazodone helps them sleep.
Hobbs: What percentage of your Phen-Prozac patients have lost weight?
Anchors: Twenty-eight percent of my patients reached ideal body weight; 50 percent lost a significant amount of weight but plateaued; and the remaining 22 percent did not take the medicine or were lost to follow-up. I’ve only had 14 patients out of 1058 √? just over one percent √? who took the medicine and did not lose weight.
Hobbs: What do you do when patients reach their target weight?
Anchors: About 25 percent of patients are able to stop taking the medicines, and the other 75 percent still need a small dose to maintain their lower weight.
Hobbs: What do you mean by a small dose?
Anchors: Typically, 15 mg of phentermine plus 10 mg of Prozac every other day for some weeks of the month.
Hobbs: Do patients tend to regain weight after the initial 6 months of weight loss?
Anchors: Except in one case, I have NEVER seen a patient regain more than 10 pounds while taking the medicines. The one exception was one of the six people who lost 150 pounds. She regained 70 lbs while taking up to 90 mg of phentermine and low-doses of an SSRI. This is the only time I have ever tried 90 mg of phentermine, but it just didn’t work. I have no idea what’s going on with her. She reached a plateau from the underside! I offered her gastroplasty surgery, but her insurance is foot-dragging, so we are really waiting for other medicines to come out.
Hobbs: Have you tried 5-hydroxytryptophan (5-HTP) combined with phentermine?
Hobbs: What dietary advice do you give?
Anchors: I suggest my patients follow my 10 commandments. They are…
1. Eat only when hungry, eat slowly and stop when full.
2. Don’t even buy what you shouldn’t eat.
3. Get aerobic exercise.
4. Fill your plate with side-dishes first.
5. Eat less of foods from land animals.
6. Choose restaurants with smaller portions.
7. Eat foods that are spicier and more aromatic.
8. Reduce alcohol intake.
9. Drink two big glasses of water with each meal.
10. Don’t stay up late eating.
It is also equally important to remove any interfering drugs and behaviors. Follow-up is also very important. I used to have patients come in every month for follow-up, but now I follow-up with a majority of them via email. It works very well. Simply handing patients a prescription without instructions on diet and exercise just doesn’t work.
Phen-Prozac: Adding 5-HTP helpful about half of the time
This is an update to the Interview with Dr. Michael Anchors which appeared in Obesity Research Update September/October 2000.
Dr. Michael Anchors has found that adding 5-HTP to Phentermine-Proac helps about half of plauteaed patients to lose more weight.
Michael Anchors, M.D., Ph.D. was the first to describe the use of phentermine combined with Prozac (fluoxetine) and other SSRIs in his best-seller Safer Than Phen-Fen (Prima Publishing, 1997). He is a clinical professor of medicine at Georgetown University and has a family practice in Gaithersburg, Maryland. A little over a year ago he started adding 5-hydroxytryptophan (5-HTP) in some of his patients taking Phen-Prozac. Larry Hobbs interviewed Dr. Anchors by email to find out what effect, if any, it has had.
Dr. Anchors can be reached at:
Michael Anchors, MD, PhD
16220 Frederick Rd Ste 210
Gaithersburg, MD 20877
(301) 990-6061
(301) 990-6064 Fax
.(JavaScript must be enabled to view this email address)
Hobbs: How many patients have you treated with Phen-Prozac√?a combination of phentermine and an SSRI?
Anchors: 1706 patients.
Hobbs: How many have reached ideal body weight√?a body mass index (BMI) less than 25?
Anchors: 521.
Hobbs: Has weight regain been a problem?
Anchors: No. Only one patient has gained back more than 10 pounds.
Hobbs: How often do you use each of these SSRIs or drugs with phentermine and what doses do you use?
Anchors: My answers to this question are based on my current practice. Most of the drugs marked 0% were tried previously and did not work.
- Prozac (fluoxetine) 10-20 mg in 70 percent of patients.
- Desyrel (trazodone) 50 mg in 8 percent of patients.
- Zoloft (sertraline) 50 mg in 5 percent of patients.
- Celexa (citalopram) 20 mg in 4 percent of patients.
- Effexor XR (venlafaxine) 75 mg 2 percent of patients.
- Luvox (fluvoxamine) 50 mgin 1 percent of patients.
- Paxil (paroxetine)—Never. Paxil can cause weight gain.
- Wellbutrin (bupropion) —Never. Wellbutrin did not work for me.
- Serzone (nefazodone)—Never. Serzone did not work for me.
Hobbs: How do you decide which drug to use?
Anchors: I use Prozac first unless the patient is already on one of the five other effective SSRIs, in which case I leave the patient on their current SSRIs although I sometimes adjusting the dose downward since higher doses of SSRIs block the effect of phentermine (see Padla in NAASO abstracts November 1997). Prozac works fine for two-thirds of patients. In the other one-third I have to switch to another SSRI such as Celexa, Luvox or Effexor when a patient reports anorgasmia, that is inability to orgasm, or switch them to Trazodone if they report having insomnia.
Hobbs: What side effects are most common with each drug?
Anchors: The only side-effect specifically traceable to the SSRI is anorgasmia, that is inability to orgasm. It occurs more often in women than men. In those cases I switch them to Celexa or Effexor which are less likely to cause this problem. The SSRI’s seldom have side-effects with the small doses that I use. The side effects that patients report most often√?dry mouth, insomnia, fast heartbeat, sweating, etc.√?are caused by the phentermine, but they are not a problem for most people. Most of these side-effects, if they occur at all, occur to a mild degree during the first ten days as the patient is adjusting to the medication and then go away. That is why it is so important for physicians to start phentermine at a dose of 15 mg per day, and then only after the patients gets used to the medicine to increase it to 30 mg.
Hobbs: Do you ever add 5-hydroxytryptophan (5-HTP) to Phen-Pro (Phentermine-Prozac or other SSRI)?
Anchors: Yes.
Hobbs: In what percent of patients?
Anchors:
Hobbs: When do you add 5-HTP?
Anchors: Whenever a patient’s rate of weight-loss slows down and their hunger increases.
Hobbs: Does it help to break plateaus?
Anchors: Yes. That’s exactly what it does.
Hobbs: How often does it work?
Anchors: About half the time.
Hobbs: Does it reduce cravings?
Anchors: It’s difficult to say. The idea of √?cravings√? means different things to different people.
Hobbs: Does 5-HTP help reduce the symptoms of PMS?
Anchors: I don’t know. Many patients have reported a reduction in PMS with the initial use of an SSRI and since I don’t add the 5-HTP until later I don’t have a way of separating out the two.
Hobbs: Do you know why it is that sometimes 5-HTP doesn’t help?
Anchors: I don’t know for sure. Maybe their renewed hunger wasn’t caused by a reduction in serotonin. Or maybe the patient didn’t really have renewed hunger, but instead only claimed renewed hunger to cover for their behavior of eating when they weren’t hungry. I don’t really know.
Hobbs: Do patients notice any subjective differences when 5-HTP is added to Phen-Pro?
Anchors: A few patients have reported having nausea with the addition of 5-HTP, otherwise they have not reported any other differences.
Hobbs: Does it provide better appetite suppression?
Anchors: Yes, it definitely does in people who respond.
Hobbs: Does it help to reduce night time eating?
Anchors: I don’t know. I haven’t asked.
Hobbs: Have patients reported any effect improvement in insomnia, headaches, PMS, fibromyalgia?
Anchors: No, not that I have been told.
Hobbs: What is the average weight loss with Phen-Prozac vs Phen-Prozac-5HTP?
Anchors: I don’t know as far as total weight loss because everyone is started on Phen-Prozac and then 5-HTP is added later. The initial weight loss with phen-Prozac ranges from zero to 5.8 pounds per week with the average being about two pounds per week. After six weeks the rate usually settles down to somewhere between zero and three pounds per week with an average of about 1 pound per week. When a person plateaus and has stopped losing weight and I add 5-HTP weight loss returns to about one pound per week.
Hobbs: Do patients report any effect on mood with the addition of 5-HTP?
Anchors: No. I haven’t had anyone tell me that it has affected their mood.
Hobbs: Do patients report any effect on energy or fatigue?
Anchors: No.
Hobbs: Have you had any reports of daytime sleepiness?
Anchors: No.
Hobbs: What time of the day do you give it√?before meals or before bedtime?
Anchors: I found and patients have reported less nausea when 5-HTP is taken with food.
Hobbs: Is 5-HTP any less effective when taken with food?
Anchors: No. I’ve found weight loss to be the same whether they take it with food or on an empty stomach.
Hobbs: Do you ever vary the dose depending on the response, that is increase the dose if it doesn’t seem to be working?
Anchors: I would if it was necessary but the response seems pretty consistent in people who respond. I’ve had only one patient out of more than a hundred say that they found that 100 mg per day had no effect on their appetite, but increasing it to 200 mg was effective.
Hobbs: What is the smallest dose that you have found effective?
Anchors: 100 mg. 50 mg is simply not enough. This is one reason I am confident that the effect from 5-HTP effect is not a placebo effect.
Hobbs: What is the largest dose that you have found necessary?
Anchors: 200 mg.
Hobbs: Do you ever vary the dose depending on a woman’s cycle or if a person is under additional stress?
Anchors: No.
Hobbs: Do you keep patients on 5-HTP continuously?
Anchors: Yes, generally I have patient continue to take it, but I also tell them they can stop if they want to and see if their hunger returns at which time they can begin taking it again. However most of my patients have wanted to continue taking it for fear of gaining the weight back.
Hobbs: Do you have any patients taking it intermittently only when they feel it is necessary?
Anchors: A few, but not many.
Hobbs: Have you noticed any difference in response between men and women?
Anchors: Yes. Women are much more likely than men to respond to 5-HTP. But this may be because women are more honest with me about the return of hunger. Men are better at denial and rationalizing, and worse at following instructions or deferring to authority.
Hobbs: Have you found any difference in the response to 5-HTP depending on which SSRI you used?
Anchors: I don’t know. I haven’t looked at this.
Hobbs: With the addition of 5-HTP how much more common are: Nausea? Headaches? Sexual dysfunction?
Anchors: Nausea is the only problem. I have not had any reports of headaches or sexual dysfunction with 5-HTP.
Hobbs: Have you had any suspected cases of serotonin syndrome with the addition of 5-HTP?
Anchors: No. And I have carefully watched for this.
Hobbs: Have you tried adding carbidopa with 5-HTP as Richard Rothman suggests? If so, was it helpful? And did it cause any additional side effects?
Anchors: Initially I only gave 5-HTP with carbidopa. But later I found that 5-HTP alone was more effective, much better tolerated, and much cheaper. Theoretically it seems that 5-HTP-plus-carbidopa should work better, but this was not my experience.
—END
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