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Pharmacy and Medications

Dosage Equivalencies

03/10/2011

Question:

What is the equivalent dose of dessicated porcine thyroid to replace 100mcg of Levoxyl? The dessicated thyroid comes in milligrams so it appears that the numbers don`t translate directly.

Answer:

The reason that the numbers do not translate directly is that the desiccated thyroid (ArmourTM Thyroid) product is a natural product derived from porcine thyroid containing both T4 (levothyroxine) and T3 (liothyroxine) in a ratio of 4.22:1. Levoxyl® on the other hand is a synthetic compound containing only levothyroxine (T4).

The general conversion used for switching from Levoxyl® to desiccated thyroid is generally 25mcgs of Levoxyl® for every 15mgs (1/4 grains) of desiccated thyroid. So when switching from 100mg of Levoxyl®, the equivalent dose of desiccated thyroid would be 60mgs (1 grain).1

1. Drug facts and Comparisons:2009 Edition. Wolters Kluwer Health; 2009:486-95

Answer submitted by Charles Skluzacek, Ohio State University-College of Pharmacy, PharmD Candidate, Class of 2011

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Response by:

David Baker, PharmD, DABAT
Formerly, Clinical Assistant Professor of Pharmacy
College of Medicine
The Ohio State University