Phentrol is based on the prescription ingredient Phentermine and works as an appetite suppressant to reduce weight in obese patients when used in short term combination with diet, exercise, and behavioral modification. It is typically used for those who are at increased medical risk in association with their weight, and it works by controlling the release of certain chemicals in the brain associated with appetite. It works with neurotransmitters in the brain, and it is a centrally acting stimulant. Its effectiveness generally ranges from about 5-12 weeks depending on the individuals, after which a cessation of use should occur with patients. All potential side effects of Phentermine should be reported to your doctor with Phentrol.