Can You Take Armour Thyroid With Phentermine?

In our latest question and answer, the pharmacist discusses whether or not Armour Thyroid can be taken with Adipex-P (phentermine).

Jan 20, 2018

Ivonne5 asked

I have been taking Armor Thyroid (dessicated thyroid( for several years. I was recently prescribed Adipex-P (phentermine) for 30 days to kick start some necessary weight loss. I am wondering if these two medicines can be take together at the same time - since they both say to take on an empty stomach before breakfast.


Armour Thyroid should be taken on an empty stomach with a glass of water at least 30 minutes prior to breakfast. Adipex-P (phentermine) should be taken before breakfast or 1-2 hours after breakfast. Armour Thyroid is more sensitive to decreased absorption if taken with food or other drugs. Some drugs can reduce the absorption of Armour Thyroid and other thyroid medications. These include drugs containing aluminum or calcium salts, cholestyramine, and antacids. Adipex-P does not contain any of these ingredients, but it is unclear whether it would affect thyroid absorption.

Taking Armour Thyroid And Phentermine Together

It may be best to take Armour Thyroid 30-60 minutes prior to breakfast and take Adipex-P at least 1-2 hours after breakfast. Both drugs should be absorbed well in this scenario as Adipex-P is not significantly impacted by food according to the manufacturer.

There is a moderate drug interaction when taking thyroid hormones along with sympathomimetics such as Adipex-P. A "sympathomimetic" is a synthetic medication which stimulates the sympathetic nervous system. Well know stimulants include:

  • Epinephrine
  • Norepinephrine
  • Amphetamine Salts

Both Armour Thyroid and phentermine can increase stimulation on the cardiovascular system. This could be significant in patients with heart disease. Adipex-P is contraindicated in patients with heart disease, stroke, or high blood pressure. Treatment should be discontinued in patients who experience new onset breathing problems, chest pain, fainting, or swelling of the lower extremities.

Adipex-P is generally only indicated for short-term use for weight reduction. Additionally, it is recommended to complement usage with lifestyle modifications including diet and exercise. Phentermine has a similar mechanism as amphetamines and is classified as a type of sympathomimetic. This stimulates the CNS, may elevate blood pressure, and reduces appetite.

In the 1990’s, phentermine was commonly prescribed with fenfluramine. This combination, known as “fen-phen” was linked to an increased risk of heart valve disease in women. Fenfluramine and dexfenfliuramine were soon taken off the market, but phentermine has remained. Phentermine has been associated with pulmonary hypertension and cardiac valve disease. Phentermine may also cause dizziness, sleeplessness, and tremor due to its sympathomimetic effects.  


Source: Adipex package insert, Armour Thyroid package insert, NY Times

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