FDA first approved Phentermine in 1959. Phentermine hydrochloride is an appetite suppressant drug, similar to amphetamine and is widely available all over the world since 1970s. It was previously sold as Fastin from King Pharmaceuticals for SmithKline Beecham; however in 1998 it was removed from the market. Medeva Pharmaceuticals sells the name brand of phentermine called Ionamin and Gate Pharmaceuticals sells it as Adipex-P. Phentermine is also currently sold as a generic.

Phentermine is a very critical drug for administration due to its addictive property. It is only prescription drug; not an over the counter drug. Phentermine is prescribed for no more than 12 weeks, due to its drug dependence properties. The usual dose is one tablet early morning, half to one hour before breakfast.

Understanding the working of Phentermine:

Phentermine acts on the central nervous system and suppresses the appetite centre; hence decreasing the potential for hunger. It also increases blood supply and blood pressure, thus a person will feel less hungry and will feel fuller for a longer time. Phentermine is similar to amphetamine in clinical physiology; hence it also has addictive properties.

Possible Adverse Effects:

Like so many other drugs, Phentermine also has some potential side effects. Out of these side effects more common side effects are:

Insomnia.
Increased blood pressure.
Irritability.
Nervousness.
Sense of well-being.
Blurred vision.
Change in sexual desire.
Clumsiness.
Confusion.
Diarrhea.
Dizziness.
Dry mouth.
Headache.
Irregular heartbeat.
Nausea or vomiting.
Psychosis.
Skin rash or itching.
Stomach pain.
Tiredness.
Unpleasant taste.

The persistence of these side effects and worsening and exaggeration of the already present side effects need immediate care and the doctor should be informed immediately.

Overdosing:

The presence of the following symptoms is highly indicative of overdose. In case of overdosing, a visit to the doctor is a must and the immediate treatment for overdose is required.

Confusion.
Convulsions (seizures).
Dizziness.
Fast Breathing.
Fever.
Hallucinations.
Hostility with urge to attack.
Irregular blood pressure.
Irregular heartbeat.
Lightheadedness or Fainting.
Mental Depression, following a period of excitement.
Tremors, Trembling, or Shaking.
Overactive Reflexes.
Panic.
Restlessness.
Severe nausea, vomiting or diarrhea.
Stomach cramps.

Precautions:

The specific precautions are required in some patients with certain conditions. Here are these patients:

Patients susceptible to or with previous history of heart disease or high blood pressure.
Patients with mild arteriosclerosis (hardening of the arteries).
Patients with an overactive thyroid gland.
Patients with history of glaucoma.
Patients who are in an agitated state.
Patients with history of drug or alcohol abuse.
Mild to moderate diabetics.
Patients with history of epilepsy or another seizure disorder.
Women who want to concieve.

Contraindications:

There is a long list of patients who can not take Phentermine at all, and these patients are:

Hypertensive patients who have moderate to extensive hypertension, uncontrolled hypertension or have serious risks relating hypertension.
Patients with advanced arteriosclerosis.
Patients with moderate to severe valvular diseases.
Patients with uncontrolled diabetes.
Pregnant women.
Breast feeding mothers.
Patients who have used MAO inhibitors in last 14 days.
Patients with sinus congestions.
Patients who have extensive anxiety states.
Patients with epilepsy or seizure disorders.
Alcohol abusers.
Drug abusers.
Patients with history of Bulimia and Anorexia.

Enlisted Drug Interactions:

Medications to treat high blood pressure.
Insulin or diabetes medication you take by mouth.
Guanadrel (Hylorel).
Guanethidine (Ismelin).
Antidepressants such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem), fluvoxamine (Luvox), paroxetine (Paxil), or sertraline (Zoloft).
Antidepressants such as amitriptyline (Elavil, Etrafon), amoxapine (Ascendin), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Janimine, Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), or trimipramine (Surmontil).
Certain herbal supplements.
Certain multivitamins.
Other weight loss medications.

Before the doctor prescribes phentermine to anyone, it is of utmost importance that the patient should tell all the medications he/she been using specially in the last month and specifically which they are still taking. Phentermine is only prescription drug and should not be used as over the counter medicine.