Editorial: Quality Assurance in Compounding, Part 7

United States Pharmacopeia (USP) Chapter <841> Specific Gravity

Specific gravity can be used for a number of quality assurance tests in a compounding pharmacy. It can be used to confirm the identity of liquids received and compared to the Certificate of Analysis or other standard, such as the USP-NF monographs. It can also be used to help confirm the general composition of a routinely compounded liquid preparation. For example, an oral liquid containing a large percentage of alcohol may have a specific gravity of less than 1.00; one containing a large amount of dissolved solids will have a specific gravity of more than 1.00. It has also been used in converting volume to weight for automated parenteral nutrition compounding devices.

Specific gravity is the ratio of the weight of a substance to the weight of an equal volume of distilled water at the same temperature. The methods used to determine the specific gravity of liquids include a pycnometer, Westphal balance, hydrometer, and weighing the exact volume of a liquid. Additionally, in some cases, the refractive index of a liquid can be correlated to its specific gravity. The most common methods include the pycnometer and weighing an exact volume of a liquid.

Pycnometers are generally available in 5- to 15-mL volumes. The pycnometer should be cleaned with water, then alcohol and allowed to thoroughly dry. It is then weighed and filled to the mark with the liquid sample. It is again weighed and the weight of the pycnometer subtracted to obtain the net weight of the liquid. The weight is then divided by the volume of the pycnometer to obtain the specific gravity.

Specific gravity can be used to confirm the volume of graduates, syringes, pipets, etc. Using water with a specific gravity of 1, a graduated cylinder containing 100 mL of water should weigh 100 grams net weight. When emptied into a tared plastic weigh-boat, the water from a 10-mL syringe should weigh 10 grams.

Also, hydrometers are available that are placed in the liquid and the specific gravity is indicated on a graduated scale on the upper tube of the device.

Specific gravity is a simple and useful technique that can be incorporated into several procedures in a compounding pharmacy.


Loyd V. Allen, Jr., Ph.D., R.Ph
Editor-in-Chief

USP is conducting a survey regarding compounded medications used in pediatric and geriatric patients to determine the most frequently compounded medications and how often these medications are requested. USP is interested in providing quality standards for compounded medications in order to assist those practitioners who provide this service to patients, and to ensure that the medications compounded are safe for patients and consumers.

Every respondent, who completes the survey and provides their name, address, and e-mail, will receive a $5.00 gift certificate to Starbucks. As a further incentive, the first 10 respondents will receive a free USP Pharmacists' Pharmacopeia (a $225.00 value). For more information see http://www.usp.org/hqi/pharmInfo/compoundingPharmSurvey.html

FDA warned pharmaceutical manufacturers, suppliers, drug repackers, and healthcare professionals who compound medications using glycerin of the importance of assuring that the glycerin used is not contaminated with diethylene glycol (DEG), a known poison used in antifreeze and as a solvent. Glycerin is a sweetener commonly used worldwide in liquid over-the-counter and prescription drug products. Although, at the present time, FDA has no reason to believe that the U. S. supply of glycerin is contaminated with DEG, it is aware of reports from other countries over the past several years in which DEG contaminated glycerin has caused human deaths. FDA emphasizes the importance of testing glycerin for DEG due to the serious nature of this potentially fatal problem. FDA issued guidance to industry recommending methods of testing glycerin and other controls to identify any contamination with DEG before using glycerin in the manufacture or preparation of pharmaceutical products.

Read the complete 2007 safety summary, including a link to the FDA's News Release regarding this issue at: http://www.fda.gov/medwatch/safety/2007/safety07.htm#Glycerin

This Regulatory Update has been provided by the American Pharmacists Association.

Your Feedback is Needed: FDA to Hold a Public Hearing on Use of Medication Guides
June 12-13, 2007, the FDA's Center for Drug Evaluation and Research (CDER) will hold a public meeting to obtain feedback on the Medication Guide program. APhA is concerned with the growing number of Medication Guides and the logistics for handling them in the pharmacy and would appreciate your feedback as we develop our comments to the FDA...Provide your feedback to APhA at http://r.listpilot.net/c/aphanet/1c8vcw0/deee

NPI Application Reminder
While CMS is implementing a contingency plan that will allow acceptance of legacy provider numbers for most covered entities (including pharmacists) that will not meet the NPI deadline, the requirement to use the NPI remains. HIPAA covered entities, including pharmacists, are required to begin using the NPI by May 23, 2007. See if NCPDP has current NPI information for you or your pharmacy at http://r.listpilot.net/c/aphanet/1c8vcw0/de74 ...Apply for an NPI online at http://r.listpilot.net/c/aphanet/1c8vcw0/c6c0

The Library CDs contain each issue of the Journal published during the respective calendar year while the Themed CDs contain all articles published from 1997-2006 about a particular topic. Take a look at all 21 CDs available at www.ijpc.com/products

Home Health Quality Improvement Campaign 2007
Learn about the Home Health Quality Improvement National Campaign 2007 at www.homehealthquality.org/hh/

Hospice Care Does Not Hasten Death, Study Shows
Researchers hope a new study will help dispel the myth that medications used in a hospice to relieve pain and other symptoms hasten death. On the contrary, they've found that hospice care may actually prolong life. See http://tinyurl.com/365wv7

Check out the dermatomes chart available to help treat pain patients at www.ijpc.com/Products/ProductDescription.cfm?PID=2466

Better Capsules
When encapsulating powders using a capsule machine, better results can be obtained by: Keeping the plastic scraper vertical (perpendicular) and simply moving the powder over the holes. If the scraper is held at an angle, then there is some pressure exerted on part of the holes resulting in some holes having tighter packing than others. Moving the scraper while holding it vertical, allows the powder to "drop" down into the holes the same as large scale capsule machines function.

Next week, how to use the tamper—another tip to obtain uniform capsules with very close tolerances.