Phentermine is a tablet that helps to reduce weight. This usually shows complete absorption after administration. It absorbs from the gastrointestinal tract and reaches maximum concentration in blood. The absorption rate differs for different composition of the dosage form. Absorption from hydrochloride salt is higher than absorption from the resin complex. It stays in the body till complete excretion of the drug through urine either in metabolized or unchanged form.
Role of the other factors in its removal:
Different factors like metabolism of the patient, age, height, duration of use, body fat and dose-effect its removal. Normally it leaves the body in 2 to 3 days but exercise and drinking more fluid speeds up its removal from the body.
Duration of phentermine’s stay in the blood:
After absorption in the body, it comes into the blood circulation and is expected to present in blood up to 24 hours after administration (typical dose of 37.5mg). If the dose is higher, the duration of the stay becomes longer. Phentermine shows 17.5% plasma protein binding means the remaining drug is available for action.
When does it start functioning in the human body:
Phentermine starts working in 3 to 4 hours after taking the tablet. In the case of the extended-release capsule, it is administered once in a day and in the case of tablets, it is administered 3 times a day. So it does not take it much time before it starts working in the human system.
The half-life of the Phentermine:
Half-life is the time, which is taken to metabolize half of the dosage of the drug or excrete unchanged drug in urine. The terminal half-life of phentermine is approximately 25 hours but it depends on the pH of urine. If the PH of the urine is acidic then the elimination half-life of the drug becomes 7-8 hours (pH <5)
The duration of its stay in the urine:
The route of excretion of the phentermine is mainly urine. Almost 70-80% of administered dose remains unchanged and the remaining dose gets metabolized by the liver. Phentermine can be detected in urine for 1 to 4 days which may vary depending on the dose. The detection of the presence of the drug is mostly performed by urine tests. Urine acidification affects the stay of phentermine in the urine. The half-life of phentermine decreases from 25 hours to 7-8 hours because of more acidic PH.