Question 20 from the first paper of 2009 asks the candidates to define ideal body weight, as a segue into a discussion of pharmacokinetic changes in morbid obesity. Apart from the ideal body weight, other measures of body composition play a role in pharmacokinetics. These include the total body weight, the body surface area index, the lean body weight, and the predicted normal weight. Drug dosing in the instructions of the manufacturer may favour one measure over the others, and specific pharmacokinetic properties of various drugs may influence which weight measure you choose to calculate their weight-adjusted dose.
Information regarding this specific topic is quite hard to find. The de Baerdmaeker article from 2004 is probably the most illuminating in terms of discussing ideal body weight and lean body weight. Ingrande and Lemmens (2010) discuss the other measures in brief. These articles were used a sources for the summary offered below.
De Baerdemaeker, Luc EC, Eric P. Mortier, and Michel MRF Struys. "Pharmacokinetics in obese patients." Continuing Education in Anaesthesia, Critical Care & Pain 4.5 (2004): 152-155.
Cheymol, Georges. "Effects of obesity on pharmacokinetics." Clinical pharmacokinetics 39.3 (2000): 215-231.
Wells, J. C. K., and M. S. Fewtrell. "Measuring body composition." Archives of Disease in Childhood 91.7 (2006): 612-617.
Ingrande, J., and H. J. M. Lemmens. "Dose adjustment of anaesthetics in the morbidly obese." British journal of anaesthesia 105.suppl 1 (2010): i16-i23.
Mosteller, R. D. "Simplified calculation of body-surface area." The New England journal of medicine 317.17 (1987): 1098.
Gurney, H. "How to calculate the dose of chemotherapy." British journal of cancer 86.8 (2002): 1297-1302.
Gurney, Howard. "Dose calculation of anticancer drugs: a review of the current practice and introduction of an alternative." Journal of Clinical Oncology 14.9 (1996): 2590-2611.