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Phentermine

Phentermine is a phenethylamine primary used as an appetite suppressant. It is typically prescribed for individuals who are at increased medical risk because of their weight, as opposed to cosmetic weight loss. more...

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Phentermine is sold either as an immediate-release formulation (Adipex®) or as a slow-release resin (Ionamin®, Australia:Duromine®).

History

Phentermine is one of two drugs in the Fen-phen anti-obesity medication, the other being fenfluramine or dexfenfluramine. Fenfluramine was withdrawn from the U.S. market in 1997 after reports of valvular heart disease and pulmonary hypertension.

Phentermine is still available by itself in most countries, including the U.S. However, because it is similar to the amphetamines, individuals may develop an addiction to it. Hence, it is classified as a controlled substance in many countries. Internationally, phentermine is a schedule IV drug under the Convention on Psychotropic Substances (PDF file). In the United States, it is classified as a Schedule IV controlled substance under the Controlled Substances Act.

Mechanism of action

Phentermine, as many other prescription drugs, works with neurotransmitters in the brain. It is a centrally-acting stimulant chemically related to the amphetamines. It stimulates neuron bundles to release a particular group of neurotransmitters known as catecholamines; these include dopamine, epinephrine (also known as adrenalin), and norepinephrine (noradrenaline). This is the same mechanism of action as other stimulant appetite suppresants such as sibutramine, diethylpropion, and dextroamphetamine.

The neurotransmitters signal a fight-or-flight response in the body which, in turn, puts a halt to the hunger signal. As a result, it causes a loss in appetite because the brain does not receive the hunger message.

Clinical use

Generally, it is recommended by the FDA that phentermine should be used short-term (usually interpreted as 'up to 12 weeks'), while following nonpharmacological approaches to weight loss such as healthy dieting and exercise. However, recommendations limiting its use for short-term treatment may be controversial. One reason given behind limiting its use to 12 weeks is drug tolerance, whereby phentermine loses its appetite-suppressing effects after the body adjusts to the drug. On the contrary, it has been shown that phentermine did not lose effectiveness in a 36-week trial (PMID 11054601). However, the risk of drug addiction may be a significant reason in limiting phentermine for short-term use.

Due to the risk of insomnia, it is generally recommended that the drug be taken either before breakfast or 1-2 hours after breakfast.

Side effects

Because phentermine acts through sympathomimetic pathways, the drug may increase blood pressure and heart rate. It may also cause palpitations, restlessness, and insomnia. Additionally, individuals taking this drug on a long-term basis may develop euphoria and a psychological addiction to it. Heart valve damage and pulmonary hypertension, severe enough to cause permanent disability or death have been seen with phentermine alone.

Read more at Wikipedia.org


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You told us: in March, we asked if you've used weight-loss enhancement products. Here's what some of you told us
From Shape, 6/1/04

* I lost 50 pounds with the help of weight-loss pills, but while I was taking them, I was extremely moody and irritable. When I stopped taking the pills, I gained back 25 pounds. I would never recommend these types of products to anyone. Not only are they "quick fixes" that don't work, but they can turn you into an unpleasant person that no one wants to be around.

--Xochitl G. Ripperger, Cincinnati

* I've used several types of weight-loss supplements, and they not only provided an energy boost, but they also helped me deal with food cravings between meals.

--Judie Taylor, Odenton, Md.

* I lost 25 pounds in three months by using fen-phen (a combination of the drugs fenfluramine and phentermine) back in the mid-1990s. I quit using it when I heard about the associated risk of heart problems. I underwent extensive testing and luckily, I was healthy, but this scare was enough for me to realize that no weight-loss drug is worth harming my health. I would rather be a little heavier and healthy than be thin with a damaged heart.

--Nancy M. Szymanik, West Danville, Vt.

* I've tried many weight-loss products, and the results were the same: dry mouth, heart palpitations, headaches and insomnia--but no weight loss. Once the pill wore off, I'd be starving and eat everything in sight. No pill can ever replace a healthy lifestyle.

--Linda Yakup-Epstein, Metuchen, N.J.

* I took fen-phen in my teens and loved the results--I lost 10 pounds in a week. However, I couldn't sleep or concentrate, but that didn't matter because I was finally skinny. When the Food and Drug Administration recalled fen-phen, I had to stop using it. Not only did I gain back the weight I had lost, but I also started suffering from an irregular heartbeat, asthma and memory problems.

--Kristy Carter, Leachville, Ark.

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