Medical Advice

Phentermine vs Vyvanse: How Are Two Meds Different?

phentermine vs vyvanse

ADHD is a condition of the brain characterized by a lack of focus, impulsive actions, and hyperactive actions. Many safe ADHD medications are available in the USA and other countries with a doctor’s prescription. Vyvanse is one of the best medications that people are used to treat this disorder. Today we will discuss this medication and comparing with another medication namely Phentermine (phentermine vs vyvanse). Which will be helpful for ADHD patients as well as for obese and overweight people.

So, Let’s understand the difference between phentermine and Vyvanse on the basis of their uses, side effects, and precautions while using them.

What is Phentermine?

This is a prescription drug that helps obese and overweight people to reduce weight by combining diet and exercise. As this is a controlled substance it has a high risk of drug dependency.

This medicine belongs to the family of drugs known as anorectics and works in such a way as to decrease hunger. A person having a body mass index (BMI) of 30 more is known to be obese and people whose BMI ranges from 25 -29.9, are considered overweight. Healthcare experts can prescribe phentermine for these obese and overweight people.

What is Vyvanse?

Vyvanse is a CNS stimulant used in treating ADHD problems in grownups and in children 6 years of age or older. This drug is an FDA-approved drug. This drug is also used for treating binge eating disorders (BED) in adults.

Vyvanse is a Schedule II controlled substance. This means those people can take this medicine who have a prescription from a healthcare expert. As the misuse and overdosing chances are high of this medicine.

Differences: Phentermine vs Vyvanse Drugs

1) Uses and Function

a) Phentermine

Mostly used for weight loss in obese people, can also be used to treat certain eating disorders as BED. Although the FDA approval for this medicine is for a short-term duration up to 12 weeks, healthcare experts often recommend this drug for longer use. Phentermine with topiramate can be used for longer terms in adults who require long-term weight control.

It has been known that the average decrease in weight when taking phentermine is 3 % of one’s initial body weight after 3 months, and 5-7 % after 6 months.

This drug affects the CNS by reducing appetite. Phentermine aids in release of chemical neurotransmitters in the brain, such as norepinephrine, which restricts appetite. Reduced appetite means a reduction in the calorie intake which will ultimately lead to weight loss.

b) Vyvanse

This drug is an ADHD medication and is used to control impulsive and hyperactive behavior. It helps an individual to focus and control one’s impulse behavior.

This medicine functions by increasing the chemicals in the brain known as dopamine and norepinephrine levels. Norepinephrine is a stimulating agent and dopamine occurs naturally, helping in the stimulating effect. These together help in better concentration, control of emotions, and performing tasks more effectively at school or other places.

Almost 80 % of the people on taking this medicine, concluded that there was a major improvement in their symptoms.

2) Dosage Strengths and Doses: Phentermine vs Vyvanse

a) Phentermine

In the generic variant phentermine, the capsules are available as:

This drug is also available in the form of an oral tablet in the dosage strength Phentermine 37.5 mg

In Brand, Adipex-P is available in oral tablet form in the strengths of :

The adult dosage for weight control can vary from 15 to 37.5 mg one tablet daily, before taking breakfast or 1 to 2 hours after breakfast. The maximum dosage of the drug is 37.5 Adipex mg per day.

b) Vyvanse

Vyvanse comes in chewable tablets or capsules. This drug is available in the dosage strengths as follows-

The dosage strengths of chewable tablets are:

  • Vyvanse 10 mg
  • Vyvanse 20 mg
  • Vyvanse 30 mg
  • Vyvanse 40 mg
  • Vyvanse 50 mg
  • Vyvanse 60 mg

The starting dosage for ADHD and BED people is 30 mg one tablet daily. The Maximum dosage is 70 mg once daily.

The dosage strengths of capsules are:

The starting dosage for ADHD and BED people is 30 mg one tablet daily. The health care expert will start with a low dose and gradually increase the doses depending on the health of the patient. The dosage can vary from per day 30 mg to 70 mg.

3) Side Effects: Phentermine vs Vyvanse

a) Phentermine

Some common side effects of phentermine drug are-

  • Constipation
  • Feeling of nervousness
  • Sleeping problems
  • Increase in heartbeat
  • Increase in blood pressure
  • Dry mouth
  • Feeling of restlessness

Severe side effects can include:

  • Misuse and dependence
  • Damage to the heart
  • Pulmonary hypertension
  • Impaired functioning of the immune system

b) Vyvanse Drug

Some common side effects of Vyvanse Drug are –

  • Diarrhea
  • Loss of hunger or decrease in hunger
  • Anxiety
  • Insomnia (sleeping problems)
  • Weight loss

Common side effects in patients taking Vyvanse for BED can be:

  • Decrease in appetite
  • Dry mouth
  • Insomnia
  • Increase in heartbeat
  • Constipation

Vyvanse Serious side effects:

  • Blood circulation problems in the fingers and toes, including Raynaud’s disease.
  • Serotonin Syndrome, (a fatal condition caused by high levels of the brain chemical serotonin).
  • Cardiovascular problems can include heart attack, stroke, and increase in blood pressure.
  • Mental health problems such as depression, worsening of current psychosis (losing touch with reality), mania (feeling high and excited), and so on.

Precaution and Warnings for Both Medicines:

1) Taking the drugs as per the doctor’s prescription.

People can take this as per the doctor or healthcare expert’s recommendation like prescribed dose quantity, and dosage timings which can help the patient in getting quick relief and a speedy recovery.

2) Misuse or dependence of the drug.

Vyvanse is a Schedule II drug. It may be habit-forming. So, tell the doctor about your medical history. Stimulants have led to high blood pressure, heart attacks, and sudden death in people suffering from heart disease or high blood pressure.

3) Blood circulation problems.

Having low blood circulation in the hands, legs, feet, and arms can lead to numbness or discoloration in the feet or toes.

4) Vyvanse in pregnant women can cause premature deaths, withdrawal symptoms, low birth weight, and some toxic effects in the newborn. Before using Vyvanse talk to the doctor if going for pregnancy.

5) Phentermine has a tendency to increase the heart rate. If it happens consult with doctor as soon as possible.

6) Mental illness

Sometimes people may experience some unusual behavior like suicidal thoughts. If one is experiencing a change in mood or has a family history of mania or psychosis then one should consult with a doctor and discuss it in detail.


In conclusion, Both the medicine Phentermine and Vyvanse are FDA-approved and prescription medicines. Obese and overweight people use Phentermine to lose weight, whereas Adderall is used to treat Attention Deficit Hyperactivity Disorder in people.

Both drugs vary regarding requirements of age, dosing, and potential side effects. It comes under controlled substances and comes with dependency and abuse.

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