/publications/issue/2008/2008-06/2008-06-8587

compounding HOTLINE

Author: Martin A. Erickson III, RPh


Mr. Erickson is director of professional affairs at Gallipot Inc.


 

I have a request to compound a combination of liothyronine (T3) and levothyroxine (T4) as a "sustained- release" (SR) or "slow-release" capsule. The commercially manufactured preparations are not "SR." What is the logic?

 

Presuming that the request is based upon the special needs of a particular patient and does not duplicate therapy that could be administered using commercially manufactured drug products, compounding a capsule of this type is appropriate. T3 and T4 are administered in very small doses, which means that the pharmacist must employ aliquot dilution technique to obtain accurate dosing where a balance with readability to 1 mg is employed. (Accuracy is 20 mg.) A bolus-forming cellulose material such as Methocel E4M Premium often is included as 1/3 of the capsule formulation to permit a "medicated" bolus to form in the stomach after administration. The bolus apparently erodes as it passes through the intestine at a rate dependent upon motility, gut contents, etc, to release the drug(s). Clinical observation reportedly suggests that patients experience reduced incidence of side effects with the slower release or delayed-release form; T4 has a longer half-life than T3, but is often included in the formulation to improve patient compliance. Nomenclature is important? any terminology requiring support from time/absorption studies ("continuous release," "slow release," "extended release") should be avoided because extemporaneous compounding does not employ such studies.

E-mail your compounding questions to .

Example dilution:

7.5-mcg liothyronine capsules

Grams

Dilution (1)

Liothyronine USP

0.2

Corn starch NF

24.75

Dilution (2)

Take of the above mixture

0.75

Corn starch NF

99.25

Dilution (3)

Take of the above mixture

33.0

Methocel E4M Premium

33.0

Corn starch NF

51.15

Silica gel

0.3

Makes 330 capsules. (#1)