Diethylpropion vs. Phentermine: Differences and Similarities

The National Institutes of Health estimates that 70.2 percent of adults in the United States are either overweight or obese. Carrying around extra weight can contribute to a number of potentially dangerous health conditions, including heart disease, diabetes, high blood pressure, and high cholesterol, all of which can contribute to premature death. 

Many people try dieting but fail to maintain their weight loss or lose any weight at all. FDA-approved prescription drugs like diethylpropion and phentermine can help obese patients lose weight when combined with diet and exercise. When comparing diethylpropion vs. phentermine, which works better for the treatment of obesity?

Overview

Diethylpropion and phentermine are generic sympathomimetic prescription medications and central nervous system stimulants. The brand name of diethylpropion is Tenuate, with the brand name of phentermine being Adipex-P. Phentermine and diethylpropion are both classified as Schedule IV controlled substances by the U.S. Drug Enforcement Administration (DEA), meaning that the medications carry some risk of abuse or dependence and access to the medications must be controlled. These medications are intended for use in adults only.

Conditions Treated

Diethylpropion and phentermine are weight loss drugs that are used to help people who are significantly overweight lose weight to improve their health. Patients who are prescribed diethylpropion or phentermine must qualify to take the medication based on being either obese or are overweight with other risk factors, such as hypertension (high blood pressure), diabetes, and hyperlipidemia (high cholesterol). Doctors use the body mass index (BMI) scale, which is calculated by dividing a person’s weight in kilograms by the square of their height in meters, to determine if a person is categorized as overweight or obese. A normal BMI is considered 18.5 to 24.9. 

Phentermine Weight Loss Solutions

Obesity

People who suffer from obesity weigh significantly more than is considered ideal for optimal health. The condition is said to result from a number of different factors.The Centers for Disease Control and Prevention (CDC) defines obesity based on a BMI of 30.0 or higher. There are three classes of obesity:

  • Class I is defined by a BMI of 30 to 34.9
  • Class II is defined by a BMI of 35 to 39.9
  • Class III is defined by a BMI of 40 or higher

There are a number of serious health consequences  associated with obesity due to the strain that the additional weight puts on the body. An increased risk of diabetes, stroke, heart disease, and some types of cancer are all associated with obesity. People with obesity are also more likely to suffer from mental health problems than those who maintain a normal weight.

Overweight with other risk factors

The CDC considers people with a BMI of 25.0 to 29.9 to be overweight. While being overweight can be uncomfortable and start to cause health problems, it is not considered enough of a health risk on its own to justify treatment with prescription medications like diethylpropion and phentermine. In order to be prescribed one of the two medications, patients who fall into the overweight BMI category must also have other risk factors, such as high blood pressure, diabetes, or high cholesterol.

How They Work

Diethylpropion and phentermine are both appetite suppressants that are believed to work by affecting the levels of certain neurotransmitters in the brain, including serotonin, norepinephrine, and dopamine. These amphetamine-like drugs can be inhibitors or release more of the neurotransmitters in question. 

Researchers are not entirely sure how central nervous system stimulants like diethylpropion and phentermine work, but clinical trials have shown that people are less hungry when they have higher levels of norepinephrine, dopamine, and serotonin. 

Side Effects

Both diethylpropion and phentermine are associated with a long list of possible side effects. Adverse effects associated with diethylpropion and phentermine are classified as common and serious. 

Common side effects of diethylpropion include:

  • Dizziness
  • Difficulty sleeping
  • Nausea
  • Diarrhea
  • Dry mouth
  • Irritability
  • Vomiting
  • Constipation

Common side effects associated with phentermine include:

  • Dizziness
  • Headache
  • Dry mouth
  • Nausea
  • Increased heart rate
  • Increased blood pressure
  • Heart palpitations
  • Flushing
  • Sweating
  • Constipation
  • Diarrhea
  • Tremors
  • Nervousness
  • Restlessness
  • Irritability
  • Increased urination
  • Insomnia
  • Agitation
  • Altered libido

Some side effects associated with diethylpropion can be serious. Patients experiencing any of the following side effects should contact their doctor right away. Serious side effects of diethylpropion include:

  • Fast, irregular, or pounding heartbeat
  • Change in sexual ability/interest
  • Mental or mood changes, as evidenced by:
    • Agitation
    • Hallucinations
    • Uncontrolled anger
    • Nervousness
  • Uncontrolled muscle movements

Some side effects of diethylpropion can be life threatening. Seek medical treatment immediately if you experience any of the following:

  • Severe headache
  • Seizure 
  • Vision changes such as blurred vision
  • Trouble speaking
  • Weakness on one side of the body

Serious side effects associated with phentermine include:

  • Cardiovascular changes
  • Severe headache
  • Trouble speaking
  • Mental or mood changes, as evidenced by:
    • Agitation
    • Nervousness
    • Uncontrolled anger
    • Hallucinations
    • Uncontrolled muscle movements
  • Changes in libido
  • Weakness on one side of the body
  • Vision changes
  • Seizure 

If side effects continue or become more troublesome, seek medical advice from your healthcare provider. Additionally, be on the lookout for potential drug interactions when taking other medications.

Phentermine Weight Loss Solutions

Use

Diethylpropion and phentermine are both intended for use as short term medications to help patients lose weight. Both drugs should be combined with an appropriate diet or exercise routine and should not be used as the sole mechanism for weight loss. 

Diethylpropion and phentermine are not the same as over-the-counter diet pills, and they should only be used when prescribed by a medical professional. Both medications become less effective when taken over extended periods of time, so they are usually not prescribed for periods of longer than a few weeks.

Diethylpropion is available in both immediate release and extended release versions. The immediate release form of diethylpropion is taken by mouth, three times a day before meals. Some patients may take another dose in the evening to prevent nighttime eating. When the extended release version of the medication is used, patients typically take one dose in the mid morning. Diethylpropion is typically only taken for a few weeks at a time. 

Phentermine is most often taken once per day approximately one hour before breakfast, but some patients may use small doses of the medication up to three times per day. The sustained-release version of the medication is typically taken before breakfast or at least 10 to 14 hours before bedtime in order to minimize sleep disruption. Phentermine is typically only taken for a few weeks at a time.

Risks

As central nervous system stimulants, diethylpropion and phentermine can both have dangerous side effects in patients who have certain medical conditions. Both phentermine and diethylpropion are associated with a risk of abuse and dependence, which is part of why the medications should only be used for several weeks at a time. Patients should make sure to give their doctor a clear medical history when considering the use of either medication. 

Patients with any of the following medical conditions may not be able to use diethylpropion or phentermine safely:

  • Diabetes
  • High blood pressure, including high blood pressure in the lungs
  • Kidney disease
  • Personal or family history of substance abuse
  • Glaucoma
  • Heart problems, including fast or irregular heartbeat, previous heart attack, or heart valve problems
  • Mental health or mood problems such as anxiety, psychosis, bipolar disorder, and schizophrenia

In addition to the medical conditions listed above, patients with any of the following medical conditions may not be able to use phentermine safely:

  • Stroke
  • Overactive thyroid (hyperthyroidism)
  • Seizures

Which works better?

The effectiveness of diethylpropion and phentermine has been compared in several comparative studies. One study found that patients treated with phentermine lost significantly more weight than patients who were treated with diethylpropion over the study period of 12 weeks. 

The majority of the weight loss occurred during the last four weeks of the study. Patients treated with phentermine also showed significant reductions in blood pressure and resting heart rate compared to the diethylpropion group, which only showed reductions in heart rate. It is believed that these reductions occurred as a result of weight loss rather than as effects of the medications.

Cost

Phentermine and diethylpropion are both generic medications that are available at a low cost that is affordable for most people. The immediate release version of diethylpropion is available at a cost of approximately $15 per month, while a one-month prescription of the extended-release version of the medication costs approximately $58. A one month supply of generic phentermine will cost less than $15. Both are short-term use medications that are typically not taken for more than a few weeks at a time in order to avoid dependence. The generic drugs are covered by most forms of commercial insurance, as well as Medicaid and Medicare.

Summary

Diethylpropion and phentermine are both prescription medications intended to help patients lose body weight over a short treatment period. Studies have shown that phentermine is more effective than diethylpropion at helping patients lose weight, particularly in the last four weeks of a treatment period. However, both medications lose their effectiveness quickly and should not be taken for more than a few weeks at a time. 

Patients can save on the cost of either medication with a pharmacy discount card from USA Rx.

Sources:
https://www.cdc.gov/obesity/adult/defining.html 
https://www.cdc.gov/obesity/adult/causes.html 
https://www.dea.gov/drug-scheduling 
https://www.niddk.nih.gov/health-information/health-statistics/overweight-obesity 
https://pubmed.ncbi.nlm.nih.gov/6844367/ 
https://www.webmd.com/drugs/2/drug-7858/diethylpropion-oral/details 
https://pubmed.ncbi.nlm.nih.gov/30209803/

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