Phentermine Side Effects

by on June 22, 2012


Commonly prescribed as part of a comprehensive treatment plan for obesity, phentermine may be accompanied by a few side effects. Elevated heart rates, a rise in blood pressure, or feelings of restlessness are not uncommon during the first days of treatment, but could be serious if they persist. Dry mouth, an unpleasant taste, constipation, and diarrhea are also experienced by many users. Severe side effects can occur with phentermine as well but are much less common. These include changes in mental state and certain cardiovascular disorders.

Common Phentermine Side Effects

As the body adjusts to the medication, some people may experience some of the more common side effects of phentermine. These include:

  • Constipation
  • Diarrhea
  • Headache
  • Vomiting
  • Dizziness
  • Restlessness
  • Dry mouth
  • An unpleasant taste
  • Changes in sex drive
  • Fast heart rate
  • Increased blood pressure

These symptoms should subside with continued usage. If the side effects persist or become bothersome, discuss other treatment options with your physician.

Serious Phentermine Side Effects

Some patients may experience more severe side effects while using Adipex, Suprenza, and other phentermine medications. These side effects are rare, but can be extremely dangerous if prompt medical attention is not given. Call your doctor immediately if you experience any of the symptoms below:

  • Fluctuations or a spike in blood pressure
  • Fainting or severe dizziness
  • Shortness of breath
  • Chest pain
  • Swollen legs or ankles
  • Seizures
  • Extreme mood changes
  • Tremors or uncontrolled shaking
  • Aggressive thoughts or behaviors
  • Abnormal heartbeats
  • Confusion
  • Hallucinations
  • Insomnia or changes in sleep patterns

There may be other side effects of phentermine that are not included in this list and may not be listed on the medication insert. This is particularly true for patients taking other medications with phentermine. If you experience any other adverse symptoms, contact your doctor.

Phentermine and Cardiovascular Health

In very rare cases, patients who take phentermine may develop serious problems with their heart or lungs. These conditions include heart valve disorders and primary pulmonary hypertension, and both can be fatal.

If you experience shortness of breath with mild exertion, chest pain, fainting, swelling in the legs or ankles, or any other symptom associated with these conditions, stop the medication immediately and talk to your physician. These side effects typically occur in patients taking phentermine with other weight loss supplements or for extended periods of time.

Pre-existing Medical Conditions

Patients who suffer from certain ailments and disorders may be more likely to experience serious side effects while taking Phentermine. Individuals who have been diagnosed with any of the following conditions, either now or in the past, should discuss the benefits of taking phentermine with a qualified professional.

  • High blood pressure, regardless of whether it is controlled or uncontrolled
  • Pulmonary hypertension
  • Heart disease
  • Stroke
  • A history of alcohol or drug abuse
  • Hyperthyroidism
  • Glaucoma
  • Mental or mood disorders, such as bipolar, psychosis, or severe anxiety
  • Diabetes
  • Heart conditions like irregular heartbeat, murmurs, or valve problems
  • A history of seizures

Individuals who have PKU or other conditions that cause adverse reactions to aspartame may not be able to take phentermine dissolving tablets (Suprenza). Discuss any other health concerns that may increase the risk of phentermine side effects with your physician or pharmacist before starting your prescription.

Other Medications

It is always a good practice to keep your doctor informed of all the medications you are currently taking, including vitamins, herbal supplements, and over the counter products, but it is especially important to remember to tell your physician if you are taking any of the drugs listed below.

  • Amphetamines, such as Vyvanse, Adderall, and Dexidrine
  • Antidepressants including Cymbalta, Lexapro, Effexor XR, Wellbutrin, etc.
  • Insulin medications for depression, weight loss, or diabetes
  • Sulfonylureas for diabetes, such as glipizide
  • High blood pressure medications like guanethidine, methyldopa, etc.

Possibly fatal interactions can occur between phentermine and MAO inhibitors. Drugs like linezolid, methylene blue, procarbazine, and other MAO inhibitors should not be used while taking phentermine and should be avoided 14 days before and after the treatment as well.

Phentermine can also have adverse interactions with alcohol, caffeine, and some street drugs including cocaine and ecstasy. Individuals who are taking phentermine should avoid other products that may increase the heart rate or raise their blood pressure, as well as drugs that may increase the risk of seizures, such as phenothiazines, amitriptyline, etc.

In most cases, individuals can take Adipex, Obenix, and other phentermine medications effectively without experiencing any serious side effects. When phentermine side effects do occur, they typically improve with time and are generally worth the benefits of the treatment. Remember to use phentermine as directed and to report any unusual symptoms, side effects, or interactions promptly to your doctor.