d is more geared towards isolation of active alkaloids, and studying the pharmacokinetics
for medical benefit.(yes you were right spade22.. thanks)
Either way, try contributing rather than correcting. Most of the numbers you threw out there were accurate though.
All of these drugs lose efficiency after time, even the ones with long half lives. The reason some may appear to lose it quicker is because the ones with shorter half lives are more prone to dose escalation :).