Stanley M. Shaw
M.S. - 1959 - South Dakota State University
Ph.D. - 1962 - Purdue University
The availability of a drug for absorption from a capsule is influenced greatly by the dissolution of the capsule product in the gastrointestinal tract. Various factors such as the formulation and the manufacturing process affect the dissolution of the capsule. Commercially available sodium iodide I-131 capsules vary in formulation and the manufacturing process. Differences in the bioavailability of the I-131 from capsules prepared by different vendors could exist and could influence clinical considerations for thyroid diagnostic studies and radiothyroid therapy.
We have employed the USP XXIII dissolution test to determine dissolution profiles for diagnostic and therapeutic sodium iodide I-131 capsules from three commercial vendors. The results of the study indicated that differences in dissolution do exist between the products. Consequently, we conducted further studies with sodium iodide I-131 capsules prepared in-house to ascertain the influence of diluents, type of lubricant, and the concentration of lubricant on the invitro release rate of I-131. Lactose, calcium phosphate, a dicalcium phosphate-Avicel PH 101 mixture, and a sodium phosphate formulation consisting of lactose and L-cysteine hydrochloride were chosen as diluents. Various concentrations of talc or magnesium stearate as lubricants were mixed with the diluent formulations. The results of the study indicated that magnesium stearate decreased the dissolution rate of I-131. Increasing the concentration of the lubricant generally reduced the release rate. The same observation was made for talc as the lubricant. In addition to the lubricant, the diluent influenced the release rate of I-131 from the sodium iodide I-131 capsules.
We are in the process of determining the relationship of dissolution profiles observed with the USP XXIII dissolution test to the uptake of radioiodine in the thyroid of the cat. Hyperthyroid cats receive I-123 sodium iodide capsules prepared to provide poor vs. good dissolution profiles. Thyroid I-123 uptake is determined over time with a gamma camera and percentage uptake values calculated. Preliminary data indicate that the formulation utilized to prepare radioiodinated capsules may influence the uptake value obtained in the thyroid.
Additional studies on-going in our laboratory are related to the influence of drugs and other agents on the uptake of radioiodine in the thyroid. While it is well known that certain agents may reduce the uptake of the radioiodine and compromise the quality of a thyroid function study, data are relatively limited regarding the length of time that a problem exists. Studies are being conducted in rodents with select agents known to affect radioiodine thyroid uptake.
Alterations in Radiopharmaceutical Biodistribution
Radiopharmaceuticals, radioactive drugs, are designed to localize in organs and tissues based upon functions and or biochemical processes ongoing within the system. The radiopharmaceutical serves as a tracer to aid in determination of normal versus an altered condition that may be indicative of a pathological condition. Studies with radiopharmaceuticals are termed nuclear medicine procedures. Prescription drugs, self-care medications or agents given to a patient during another diagnostic examination may interfere with the uptake, retention or treatment of a radiopharmaceutical given to the patient. This type of situation could lead to confusion in the outcome of the nuclear medicine study and, potentially, to an improper diagnosis. Considerable information has been published as a result of clinical observations with patients. There is a need to document potential problems through controlled investigations with laboratory animals and conditions that allow extrapolation to clinical conditions in the human.
M-D. Yu, G. E. Peck, J. C. Scott-Moncrieff, W. E. Blevins, and S. M. Shaw, "The Effect of Formulation on Radioiodide Thyroid Uptake in the Hyperthryroid Cat," Drug Dev. Indust. Pharm., 25, 567-572 (1999).
M-D. Yu, T. Quinton, and S. M. Shaw, "Influence of Iodine-131 Solution Volume and Storage Time on In Vitro Dissolution," J. Nucl. Med. Tech., 26, 274-277 (1998).
S. M. Shaw, "Introduction to Nuclear Pharmacy," Int. J. Pharm. Comp., 2, 424-425 (1998)
M-D. Yu, W. S. Huang, and S. M. Shaw, "Pharmaceutical Factors That May Affect Diagnostic and Therapeutic Outcomes of Thyroid Disorders," Ann. Nucl. Med. Sci., Vol. 11, No. 2, 41-55 (1998).
S. M. Shaw, "Diagnostic Imaging: An Overview for the Pharmacist," J. Am. Pharm. Assoc., Vol. 37, No. 1, 99-108 (1997).
W. R. Widmer, S. M. Shaw, and D. E. Thrall, "Effects of Low-Level Exposure to Ionizing Radiation: Current Concepts and Concerns for Veterinary Workers", Veterinary Radiology and Ultrasound, 37 (3), 227-239 (1996).
Y. Lee, S. Shaw, and G. Peck, "The Effect of Formulation on I-131 Dissolution In Vitro from Sodium Iodide Capsules," Drug Dev. Ind. Pharm, 21, 663-673 (1995).
S. M. Shaw, "Nuclear Pharmacy and Radiopharmaceuticals," Hospital Pharmacy Times, 61 (6), 5-15 (1995).
S. M. Shaw, "Approaches to Education in Nuclear Pharmacy," American Journal of Pharmaceutical Education, 59 (3), 296-298 (1995).
S. M. Shaw, "Diagnostic Imaging and Pharmaceutical Care" American Journal of Pharmaceutical Education, 58,Ý190-193 (1994).