1 What is Adipex-P?

Brand: Adipex-P, Lonamin, Oby- Cap, Pro-Fast, Suprenza, T- Diet, Zantryl

Generic: Phentermine Hydrochloride

Adipex-P is an oral medication for weight loss in patients who are obese and who have an initial body mass index which is greater or equal to 30 kg/m2, or greater or equal to 27 kg/m2 in the presence of other risk factors such as hypertension, diabetes and hyperlipidemia. It serves as an adjunct to diet and exercise. It contains phentermine hydrochloride, a sympathomimetic amine.

Adipex-P is available as capsules and tablets, both containing phentermine hydrochloride 37.5 milligrams.


Adipex-P should be taken by mouth usually once a day. It is usually taken one hour before breakfast or 1 to 2 hours after breakfast. The dosage should be adjusted according to doctor’s instructions.

Sustained-release capsules are usually once a day before breakfast or at least 10 to 14 hours before bedtime.

You should swallow the medication whole and avoid crushing or chewing sustained-release capsules so that side effects are minimized. Do not take Adipex-P with other appetite suppressants. Do not increase the dose unless instructed by your doctor.

If you miss a dose, use it as soon as you remember. Continue to use it as prescribed by your doctor or as stated on the package label.


Adipex-P may interact with drugs such as the following:

  • Other appetite-suppressant drugs in the past year such as diethylpropion, sibutramine, or ephedra/ma huang)
  • MAO inhibitors such as isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, and tranylcypromine
  • Drugs for depression such asTCAs (imipramine, SSRIs and SNRIs such as paroxetine, fluoxetine, venlafaxine, duloxetine)
  • Drugs for diabetes such as insulin, sulfonylureas (glipizide)
  • High blood pressure medicine such as guanethidine and methyldopa
  • Phenothiazines such asprochlorperazine, promethazine and chlorpromazine
  • Other stimulants such as amphetamines, methylphenidate, street drugs such as cocaine or MDMA/"ecstasy"
  • Certain antihistamines such as diphenhydramine
  • Anti-seizure drugs such as carbamazepine
  • Medicine for sleep or anxiety such as alprazolam, diazepam or zolpidem
  • Muscle relaxants
  • Narcotic pain relievers such as codeine
  • Psychiatric medicines such as risperidone, amitriptyline, and trazodone
  • Isoniazid (INH)
  • Theophylline
  • Caffeine

Side Effects

There are no side effects known aside from a possible allergic reaction in people who have previous or unknown hypersensitivity to the drug.

Watch out for signs of allergic reactions such as:

  • Rash
  • Itching
  • Swelling


Before taking this medication, tell your doctor or pharmacist if you have the following conditions:

  • Allergy to phentermine and to other sympathomimetic amines such as pseudoephedrine, amphetamine, and diethylpropion
  • Uncontrolled high blood pressure
  • Glaucoma
  • History of alcohol or drug abuse
  • Vascular heart disease such as chest pain and heart attack
  • Mood problems such as severe anxiety, bipolar disorder, psychosis or schizophrenia
  • High blood pressure in the lungs or pulmonary hypertension
  • Stroke
  • Overactive thyroid (hyperthyroidism)
  • Diabetes
  • Controlled high blood pressure
  • Other heart problems such as heart murmur, abnormal heartbeat and heart valve problems
  • Kidney disease
  • Seizure problem
  • Pregnancy and lactation