In the Laboratory
Quality Control Analysis of Student-Generated Pharmaceutical Capsules Ehren C. Bucholtz,* Lisa M. French, Jaie P. Lavoie, and Claude J. Gaebelein Division of Basic and Pharmaceutical Sciences, St. Louis College of Pharmacy, St. Louis, Missouri 63110 *
[email protected] Whereas most drugs dispensed at the pharmacy are in readyto-take form, some drug preparations called compounds need to be made. Compounding is the pharmaceutical term for the preparation, mixing, assembling, and packaging of a drug as a result of a doctor's prescription (1). Compounds are produced for many different situations: converting one dosage form to another (e.g., oral to rectal, injection to oral); making the drugs more palatable to children; preparing a drug product that is discontinued due to low profits in manufacturing; testing new drug applications or new drugs that have not been manufactured; covering drug shortages due to miscalculations in just-in-time manufacturing; and combining multiple prescriptions to decrease number of pills taken and increase patient compliance. It is estimated that the percentage of prescriptions that are compounded approaches 11% and nearly 88% of pharmacies surveyed provided some sort of compounded drug (2). Compounding is not regulated under federal law, but under each state's board of pharmacy (3). A movement has been gaining strength to regulate compounded preparations under the Food and Drug Administration. The change in regulation is due to the increasing number of compounded prescriptions that have resulted in injury or death (4). The negative outcomes are most often attributed to issues of sterility of compounds injected or errors in potency (the quantity of drug present in a sample). A recent case involved the death of 21 polo horses in Florida attributed to an error in calculations (5). To address these issues, many pharmacy boards have instituted screening programs to ascertain quality of the products being compounded. Between fall 2003 and fall 2008, the Missouri Board of Pharmacy randomly tested 254 capsules provided by compounding pharmacies throughout the state to evaluate the quality of compounded preparations.1 Of these capsules, 25% failed to meet the labeled potency as defined by (10% of the stated mass of active compound. Of those capsules that failed, potency ranged anywhere from 0% to 250% of the stated quantity. This result met with some alarm as certain drugs have a very small therapeutic index2 and potency errors can be disastrous. To entice students who are interested in pursuing careers in health sciences into learning chemical analysis, many articles in this Journal focus on the determination of active ingredients in various over-the-counter medications (6-14). The challenge of making drug preparations provides an opportunity for students to experience the role of a pharmacist while employing skills taught in many chemistry courses. Uniform solid drug mixtures are difficult to achieve. Large-scale drug mixtures are achieved by stirring machines, but small-scale batches in community pharmacies are mixed using mortars and pestles. Because mixtures are affected by particle characteristics (size, shape, charge, and density), final active ingredient concentration, and mixing time, 1108
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it is inherently difficult using tools that pharmacists have most ready access to prepare solid drug mixtures (15). In this multiweek interdisciplinary laboratory experiment, the outcomes of a pharmacy practice laboratory are integrated with the outcomes of the organic chemistry laboratory in a scenario where students make capsules and determine if the correct potency is achieved. Although the experiment is performed as an interdisciplinary experience, it fits well within multiple courses in the chemistry curriculum. The experiment presents students with two problems: (i) preparation of a homogeneous solid mixture and (ii) spectrophotometric analysis. Description of the Experiment The experiment is completed in two laboratory periods: a 2-h laboratory period to complete the capsule formation and prescription labeling and a 3-h laboratory period to determine potency. Students receive a prescription to fill 20 hand-punched3 capsules of given active ingredient. In tablets and capsules, a second solid (lactose) is used as a diluent or excipient to help absorption, stability, and dissolution. The solids are triturated using a mortar and pestle to make particle size even, and the two solids are mixed with geometric dilution.4 Gelatin capsules are filled, capped, and weighed. The mass of the capsule contents should equal the mass of active ingredient plus an equal mass of lactose. The expectation is that students will produce capsules that are (10% of the given expected potency of the active ingredient, which is the variability allowed by United States Pharmacopeia production standards (1). Analysis is completed using ultraviolet spectroscopy. Student pairs weigh three capsules with an analytical balance to ascertain the mass of capsules as an indicator of variability. After weighing, capsules are either (i) opened and contents dissolved to make a 1 L stock solution or (ii) dissolved intact with heating to make 1 L stock solutions. Serial dilutions of the stock solutions are made to afford concentrations that would yield an absorbance of approximately 1.2 for a properly compounded capsule. Calibration curves are determined using standards provided by the laboratory manager, but standards made by students could be part of the activity. Results and Discussion To make the exercise resemble a prescription that students might encounter in a pharmacy compounding setting, we chose to have students make capsules containing either 325 mg of acetaminophen or 100 mg of caffeine. Although it is preferable to analyze ethanolic solutions, we chose to analyze aqueous solutions to decrease the cost of the experiment. In establishing
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Vol. 87 No. 10 October 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed100483c Published on Web 08/09/2010
In the Laboratory
protocols for this experiment, we were not able to discern any significant difference in analysis between aqueous or ethanolic solutions. This experiment was conducted in spring 2008 and spring 2009. In 2008, 183 acetaminophen capsules were produced. The overall failure rate based on potency was 36%. When excluding capsules that were filled improperly (capsule mass either too high or low), the fail rate was 26% with even distribution between capsules with either too high or low potency. To address the issues that might affect the variability in the active content, we (i) switched to caffeine and (ii) dissolved the whole capsule when preparing the initial stock solution to ensure complete transfer. Caffeine has a greater solubility in water and whole capsule dissolution allows for a more complete transfer of the contents. In 2009, 237 caffeine capsules were produced. The overall failure rate on potency was 34% with a 26% failure rate within the subset of capsules having allowable mass variations. This demonstrates that alteration of the protocol did not affect overall failure rate. The high failure rate can be attributed to either improper capsule formulation or to analytical technique. In a separate experiment by the authors, 3.00 g of caffeine and 3.00 g of lactose were mixed with proper geometric dilution technique.4 Eight 200 mg aliquots of the mixed material were analyzed and determined to contain 100.5 ( 1.3 mg of caffeine. To test the students' analytical ability, a randomly selected set of students was given 15 capsules made from this caffeine mixture. Student analysis of this mixture indicated a caffeine content of 105 ( 3.7 mg; only two capsules slightly exceeded the acceptable range ((10%; 113 and 111 mg). These results indicate that errors in student capsule formulation, rather than improper analytical technique, are most likely responsible for the observed variability and potency errors. This difficulty making solid mixtures is an outcome that has been previously described (15). In the student-generated capsules, the quantity of active ingredient for acetaminophen and caffeine ranged from 19% to 192% of the intended dose. The health consequences of such errors can be dire when a drug with a small therapeutic window is compounded. Variations on this experiment may include a subset of students who purposely use incorrect technique or change the ratio of active ingredient to diluent to emphasize the variability in potency errors due to trituration. Another change to the experiment resulted from misinterpretation of data by the students. Specifically, a number of 2008 students calculated quantities of acetaminophen that exceeded the mass of the capsules, but failed to recognize this as dilution error. To address this issue, we included a question in the postlab assignment in which students had to resolve this discrepancy. Hazards Caffeine and acetaminophen are harmful if swallowed in large doses and are skin, eye, and respiratory irritants. Summary Although the chemistry in this experiment is not novel, this experiment is unique in that students have an opportunity to practice chemical analysis related to the manufacture and quality control of pharmaceuticals. Students learn the challenges of making compounded pharmaceuticals and are surprised at the failure rate among practicing pharmacists and their own work. The experiment emphasizes the requirement for good technique
r 2010 American Chemical Society and Division of Chemical Education, Inc.
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in preparation of homogeneous mixtures and identifies one method to determine the quality of their product. Acknowledgment The authors thank the Missouri Board of Pharmacy for sharing capsule data analyzed between 2003 and 2008. We also thank David Mount and Rhonda Bilger for overseeing capsule production. Notes 1. The Missouri Board of Pharmacy produces annual reports for all compounded products; however, it does not publish specific data on fail rates on individual compounded preparations. Sid Werges, R.Ph. from the Board compiled data that pertain only to compounded capsules. 2. The therapeutic index is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes death. Quantitatively, it is the ratio given by the median lethal dose (LD50) divided by the median effective dose (ED50). 3. A powder mixture containing active drug is placed on a powder paper or ointment slab and leveled with a spatula to a height approximately half the length of the capsule body. The capsule cap is removed and the base of the capsule is held vertically. The open end is repeatedly pushed or “punched” until the capsule is filled; the cap is then replaced to seal the capsule. 4. Geometric dilution is described in the supporting information.
Literature Cited 1. United States Pharmacopeia 30/National Formulary 25. The United States Pharmacopeial Convention, Inc.: Rockville, MD, 2008; Chapter 1075 Good Compounding Practices. 2. Capehart, K. D. Am. J. Pharm. Educ. 2008, 72, 119. 3. Johnson, P. E. J. Pharm. Care Pain Sympt. Control 1997, 5, 47–57. 4. Brushwood, D. B.; Smith, W. T. Am. J. Health-Syst. Pharm. 2009, 66, 495–498. 5. Haas, B. Diaz, M. Los Angeles Times http://articles.latimes.com/ 2009/apr/24/nation/na-dead-horses24 (accessed Jul 2010) 6. Canepa Kittredge, M.; Kittredge, K. W.; Sokol, M. S.; Sarquis, A. M.; Sennet, L. M. J. Chem. Educ. 2008, 85, 1655. 7. Ferguson, G. K. J. Chem. Educ. 1998, 75, 467–469. 8. Hein, J.; Jeannot, M. J. Chem. Educ. 2001, 78, 224–225. 9. Simonson, L. A. J. Chem. Educ. 2001, 78, 1387. 10. Yang, S. P.; Tsai, R.-Y. J. Chem. Educ. 2006, 83, 906–909. 11. Mitchell-Koch, J. T.; Reid, K. R.; Meyerhoff, M. E. J. Chem. Educ. 2008, 85, 1658. 12. Byrd, H.; O'Donnell, S. E. J. Chem. Educ. 2003, 80, 174. 13. Walsh, T. D.; Koontz, C. S. J. Chem. Educ. 1997, 74, 585. 14. Douglas, R. H.; Muldowney, C. A.; Mohamed, R.; Keohane, F.; Shanahan, C.; Walsh, J. J.; Kavanagh, P. V. J. Chem. Educ. 2007, 84, 829. 15. Venables, H. J.; Wells, J. I. Drug Dev. Ind. Pharm. 2001, 27, 599.
Supporting Information Available Student laboratory handout including prelab and postlab questions; instructor notes. This material is available via the Internet at http://pubs.acs.org.
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