Unfortunately, many people cannot tolerate the adverse effects of NTG, and as a result, its use is often limited. The main contraindication to surgery for an anal fissure is impaired fecal continence, a state that could be exacerbated by surgery. Painkillers If you experience prolonged burning pain after passing stools, your doctor may recommend taking common over-the-counter painkillers, such as paracetamol or ibuprofen. The internal sphincter spasm is the main factor in the pathogenesis of chronic anal fissure. The internal anal sphincter, one of two muscles that control the anus, is always under tension. No other complications have been noticed.