Phentermine (fen-ter-meen) is an appetite suppressant used to help overweight and obese individuals lose weight. It primarily affects the central nervous system. Phentermine is used together with diet and exercise to treat obesity in people with risk factors such as high blood pressure, high cholesterol or diabetes. When used correctly and in conjunction with a healthy diet and activity, it results in fast and optimal weight loss. However, as with any drug, there are certain precautions and possible side effects to be aware of.
What it is Phentermine
The word phentermine is a contraction of “phenyl-tertiary-butylamine”. With pharmacology similar to amphetamines, it is a psychostimulant drug of the phenethylamine class. It’s medical usage is an appetite suppressant.
In the mid-1990′s doctors discovered that Phentermine when combined with Fenfluramine, or ‘Fen-Phen’, led to an increase in weight loss among overweight and obese patients. Fenfluramine stimulates the production of serotonin, the happy hormone that regulates mood, while Phentermine causes the body to burn more fat. However, the combination ended up causing heart damage in many patients who took the drug, and Fenluramine was pulled off the market.
Phentermine, though, was considered safe for continued use. However, it is only for short-term use as the longer it is used, the greater the chance of heart damage and tolerance.
When used in tandem with a healthy lifestyle consisting of a reduced-calorie diet and exercise, Phentermine results in fast, optimal weight loss; especially for people that are not seeing sufficient results from diet and exercise alone. However, as with any drug, there are precautions and side effects to be aware of.
How It Works
Phentermine stimulates the adrenal glands to release norepinephrine. It does so by working in the hypothalamus section of the brain. The neurotransmitter norepinephrine is a chemical messenger used to signal to our body what is often referred to as the ‘flight-or-flight response’. This response stimulates the hypothalamus which in turn begins a succession of nerve cell firing and the release of chemicals.
This stimulation and resulting firing of nerve cells and chemicals causes digestion to slow by inhibiting stomach and upper intestinal action. This also frees nutrients, especially those in the form of glucose and fat, which are typically very hard to reach in normal circumstances.
Phentermine interacts with the body’s central nervous system, muscular system and cardiovascular system. In the same pharmaceutical class as phenylethylamine and amphetamine, it has similar effects. This class of drugs stimulates neurons in the central nervous system in order to release increased levels of catecholamine. Catecholamine are a group of neurotransmitters – including adrenaline, dopamine and norepinephrine – which, when levels are raised, can inhibit messages of hunger sent to the brain. This has the effect of a decreased appetite resulting then in eating less. All of this might seem like advanced medical jargon, but it can be broken down fairly simply as follows:
Phentermine works to release adrenaline, which is a neurotransmitter responsible for the flight or fight response. When the body enters this response, the signals of hunger are blocked. Essentially, your body prioritizes the current perceived threat and decides that eating can wait until it’s resolved.
Another function of Phentermine is to indirectly affect the leptin levels in your body. Leptin is a protein hormone partly responsible for the regulation of your metabolism. Leptin also decides the rate at which energy is taken in and used. As such, when the leptin levels are increased by taking Phentermine, your brain decides the stomach is full already. It thinks your body alerady have plenty of fuel and therefore do not need to take in any more. Therefore, it is an important factor with great impact on the appetite.
The action Neuropeptide Y is also inhibited by Phentermine. This peptide is responsible for determining how much stored energy (fat) is necessary for your body. When there is a decrease in stored fat, this peptide sends a signal telling your body to rest so that no further energy is consumed. It’s often why overweight people often feel exhausted when they try to lose weight, and makes exercise difficult. If that weren’t enough, it additionally sends hunger signals so that you will eat and increase fat storage. Hence, stopping the peptide from carrying out these actions – which Phentermine does – tricks your body into burning more of these stored calories.
The exact dosage is determine by your doctor, who bases it on your medical history, condition and response to therapy. Your dosage will be adjusted by your doctor until the best level is found. Take this medicine at regular intervals and precisely as prescribed by your doctor to achieve the best results.
Phentermine is usually only taken short term, 3 to 6 weeks in duration. It should not be taken with other appetite suppressants. It often starts to lose it’s effectiveness after a few weeks of taking it.
The average adult dose for Phentermine is 37.5 mg by mouth, once a day either before breakfast or an hour or two after it. For some people, a 15 mg daily dose is sufficient, while in other cases it may be best to take 15 mg two times per day. Due to the possible side effect of insomnia, it’s best to avoid taking Pherntermine late in the evening.
Withdrawal symptoms can arise if you stop taking Phentermine suddenly. This is especially true if you have taken it for an extended period of time or in large doses. In these cases, withdrawal symptoms like depression and extreme tiredness can. Gradually reducing your dosage over time may prevent these reactions to withdrawal.
By and large, Phentermine is tolerated well if taken at the prescribed dosage and not for longer than 12 weeks. However, there are still sometimes side effects. The most common ones include a bad taste in the mouth, decreased sex drive, constipation, diarrhea, anxiety, sleeplessness, dry mouth, nervousness and upset stomach.
It’s less common, but more sever side effects include:
- Convulsions (seizures)
- Hostility with aggression
- Irregular blood pressure
- Exaggerated sense of well-being
- Light-headedness, fainting or headahce
- Fast or irregular heartbeat
- Tremors, trembling, or shaking
- Regurgitant cardiovascular disease
- Shortness of breath
- Overactive reflexes
Phentermine use is contraindicated in those who are:
- Allergic to phentermine or any of it’s metabolites (e.g. pseudoephedrine)
- Taking amphetamine (i.e. Dexedrine, Adderall, Vyvanse), bupropion (WellButrin), dexfenfluramine, fenflulramine, furazolidone, guanadrel, guanethidine
- Have taken a monoamine oxidase inhibitor (MAOI) (e.g. phenelzine) within the last fourteen days
- Subject to an overactive thyroid, high blood pressure, glaucoma, heart or blood vessel diease, diabetes, severe narrowing of the blood vessels, a brain or spinal cord disorder, high cholesterol, hardening of the arteries, or high lipid levels
- In an agitated state or have a history of substance abuse
- Pregnant, planning to become pregnant or breast-feeding
- Taking any prescription or non-prescription drugs, herbal supplement or product, or dietary supplement.
The Bottom Line
Phentermine is an amphetamine-like prescription medication used to suppress the appetite. It greatly aid your weight loss efforts by decreasing hunger and increasing energy. It should be used as part of an overall plan for weight loss, used in conjunction with a good diet and exercise. When used correctly Phentermine is a safe way to kick-start your plan and see results in fast and optimum weight loss, but it is not for long-term use.
like most drugs it has some potentially serious side effects you should be aware of, including:
- Increased blood pressure
- Dry mouth