This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Acne and chemical peeling, Subject name: Dental
Drug of choice for nodulocystic acne is: 
Select and explain. 
A. Tetracyclines, B. Azithromycin, C. Isotretioin, D. Coicosteroids
C: Isotretioin
Answer: C: Isotretioin 
Explanation: Nodulocystic acne / grade IV acne- DOC- Isotretinoin. Isotretinoin- 13 cis isomer of retinoic acid Dose :0.5-1mg/kg/ k/bwt Max cumulative dose: 120-150mg/kg/bwt