It’s common that after being on appetite suppressants for a while, you develop tolerance to it. The mechanism of this tolerance may be due to depletion of serotonin in your brain. That’s why we use an SSRI to increase the effective concentration of serotonin in the brain for phentermine to work better. The common SSRIs that we use are trazadone and fluoxetine. The other product that we use to treat this tolerance is an amino acid compound (Neuroreplete or D5). Ideally SSRI and D5 should be used together with phentermine. But due to cost (D5 costs ~$100/month), we use only SSRI ($10/month) in our standard protocol. D5 is added only after a patient has developed tolerance. This approach seems to work well for most people.
How to manage phentermine tolerance (or tolerance to other appetite suppressants)?
- First of all, determine if phentermine still works for you. If you feel any appetite suppression or increased energy after taking phentermine, then it still works.
- Next, determine how long phentermine controls your appetite. Let’s say you take a phentermine tablet around 8am and you start feeling hungry around 4pm. This means that phentermine is able to control your appetite for about ~8 hours.
- Then determine when is the best time to take your phentermine. Take the above example where you take phentermine around 8 am and feel hungry around 4pm. Let’s say your sleep time is 11 pm. So between 4pm and 11pm, there is ~7 hours without effective appetite suppression.
- Now change the time you take phentermine. In the example above, in the 7 hours before your bed time, you don’t have effective appetite suppression. You need to push the time you take phentermine ~7 hours later, from 8 am to ~3pm.
- If you take phentermine too early, you’ll feel hungry. If you take it too late, you won’t be able to sleep. You need to use what I described above to adjust the timing of phentermine to achieve your appetite suppression goal. The Goal is that you don’t feel hungry in the evening hours and you can go to sleep near your regular hours (10-12 pm for most people).