Brief Answer:
Prescription based antibiotics, metronidazole and anti-inflammatory

Detailed Answer:
Hi.

Thanks for your query, albeit short and specific.

Noted the history and understood the concerns.
I hope you mean to say fistula in ano.
Since this has a tract that extends from the inner part of anal canal and/or rectum to the skin outside, there are no products that can help to cure the fistula.
You can surely apply liquid Betadine locally to avoid secondary infection.
Take an antibiotic, metronidazole which needs a prescription from your Doctor/Surgeon.
You can take an anti-inflammatory like Ibuprofen if it suits you.
Consult a General Surgeon or a Proctologist for evaluation, investigations like Fistulogram and or MRI Fistulogram to know the type of fistula to plan for proper surgery.

Please give feedback.
I hope this answer helps you.

Take care.

With Regards.
Dr T Chandrakant.

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