This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy, Subject name: Pharmacology
Which of the following anti-HIV drug should never be given as rechallenge once history of producing allergic reaction with drug is known? 
Select and explain. 
A. Lamivudine, B. Abacavir, C. Zidovudine, D. Nelfinavir
B: Abacavir
Answer: B: Abacavir 
Explanation: Abacavir (ABC) This guanosine analogue is a potent ARV drug that acts after intracellular conversion to carbovir triphosphate. Resistance to ABC develops slowly, and it exhibits little cross resistance with other Nis. Its oral bioavailability is 80% and it is mainly eliminated by metabolism. The plasma half life is 1-1.5 hour, but intracellular half life of active metabolite is > 12 hours. Hypersensitivity reactions such as rashes, fever, flu-like symptoms are the major problems. Some fatalities have occurred when patients developing the reaction were given fuher doses of ABC. Avoidance of alcohol is advised. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:772