It's not technically possible to develop resistance to spiro, but the drug's effectiveness depended on brand, you may want to check the brand and change it to another before trying other anti-androgen.
Note: Androcur is not superior to spiro as an antiandrogen due to 5 factors:
1) substantially increasing SHBG and reducing androgen levels, thereby making less estrogen bioavailable.
2) inhibit growth hormone secretion and reduce growth hormone levels.
3) exert weak to mild androgenic action thereby weakly to mildly inhibiting breast growth.
4) reduce estrogen receptor levels, thereby making cells less sensitive to estrogen.
5) reduce natural conversion of androgens into estrogens, thru androgen depletion.