For large cystic acne, really, I feel that Isotretinoin is the best option as it goes down to the pathophysiology of reducing oil secretion. Combining it with antibiotics would solve it systemically.
Cortisone injections is a directed therapy for large cystic acne, and there is the risk of skin dimpling due to poor technique.
I would also suggest that you consider carbon laser therapy which has shown some efficacy in reducing the severity of cystic acne in a study.
Seek the right treatment after discussing with your physician
Winston
