Botulinum toxin (the main brand name is Botox) is a purified protein that, when injected into a muscle in very small, precise doses, temporarily blocks the nerve signal that tells that muscle to contract. The muscle relaxes. The effect is local — it doesn't travel around the body — and it wears off on its own over time as the nerve grows new connections.
In the internal anal sphincter (the smooth muscle ring that keeps your anus closed), the Botox effect typically lasts 3–4 months. That window is usually long enough for a fissure to heal properly. Once the Botox wears off, the muscle returns to normal — ideally with the fissure fully healed so it doesn't matter.
Several brands of botulinum toxin exist (Botox, Dysport, Xeomin). They all work the same way, though the doses aren't interchangeable unit-for-unit.
Botox injection for an anal fissure is usually the right next step if:
- Your fissure has been present for more than 8–12 weeks and hasn't healed despite consistently applying a topical sphincter-relaxant ointment (nifedipine, diltiazem, or GTN) for at least 8–12 weeks
- You couldn't tolerate the ointment — for example, GTN causes bad headaches in about half of people
- You prefer to try something before surgery and are comfortable with the published 50–75% single-injection success rate and the small risk of temporary minor leakage
- Testing has shown your sphincter pressure is elevated — confirmed on anorectal manometry (a simple pressure measurement test)
Botox is generally not the best option for fissures caused by Crohn's disease (which need a different treatment approach), or for people who already have some difficulty controlling their bowel motions, where any further change in sphincter function could cause problems.
- Severe pain with every bowel motion that has been going on for more than 8 weeks
- A fissure that a doctor can see at the back of the anal opening, often with a small skin tag at the outer edge
- Pain that hasn't improved meaningfully despite consistently using cream twice a day for 8+ weeks
- The fissure is substantially affecting your quality of life — missing work, avoiding activities, dreading the toilet
- A wound that looks fibrous and pale at the base rather than fresh (a sign it's been there a while)
Botox injection for a fissure is a short day procedure — you come in, have it done, and go home the same day. It's done under light sedation or a brief general anaesthetic, not just local anaesthetic, because the injection needs to be precise and the area needs to be properly relaxed.
Before the procedure: Don't eat or drink for 4–6 hours beforehand (standard fasting for anaesthetic). No special bowel preparation is needed. The procedure itself takes about 15–20 minutes in theatre, plus time to recover from the anaesthetic.
The injection: While you're under anaesthetic, the internal anal sphincter — a ring of smooth muscle just inside the anal canal — is located. A small amount of diluted botulinum toxin (typically 20–40 units) is injected directly into the muscle, on one or both sides of the fissure.
Recovery: You'll go home the same day, usually within 2–3 hours of finishing. You'll need someone to drive you home because of the anaesthetic. Most people feel essentially fine by that evening.
Afterwards: Keep up your stool softeners, high-fibre diet, and warm sitz baths. The Botox starts working within 24–72 hours, and most people notice their bowel motions are less painful within the first week. You may also be asked to continue your topical sphincter-relaxant ointment while the fissure heals.
Your fissure isn't healing because the sphincter muscle is in constant spasm — this raises the pressure inside the anal canal, physically pulls the wound edges apart with each bowel motion, and reduces blood flow to the area (which is already limited at the back of the anal canal). Reduced blood flow is a key reason wounds can't heal.
Topical creams help by gently reducing that muscle spasm — but their effect is modest. Botox produces a more sustained drop in resting pressure for 3–4 months. That allows blood to reach the wound and the fissure to close. It's the same problem being tackled more directly.
Contact your surgeon if any of the following happen:
- Your pain is getting noticeably worse rather than better in the first 2 weeks
- You develop a fever or signs of infection around the area
- You're experiencing persistent leakage of solid stool — this is unusual and worth reporting
- The fissure still hasn't healed by 12–16 weeks after the injection
In published series, around 2–10 in every 100 people experience some temporary minor leakage of wind or liquid stool while the Botox is active. This is temporary, and resolves as the Botox wears off over 3–4 months.
Success rate
In published series, around 50–75% of chronic anal fissures heal after a single Botox injection, when stool-softening measures are kept up alongside. That makes it a useful middle step — published results are typically higher than ointment alone (around 65–75% with consistent use) and with a lower recovery burden than surgery (which heals more than 90% of cases).
Recovery timeline
Most people notice that bowel motions hurt less within the first week. By 2–4 weeks, the improvement is usually substantial. The fissure itself heals progressively over 6–12 weeks. By 3–4 months, the Botox effect has fully worn off and the sphincter is back to normal — hopefully with the fissure healed and behind you.
What if it does not work?
Around 25–50% of chronic fissures don't fully heal after one Botox injection. If that happens, a second injection can be tried, or lateral internal sphincterotomy may be discussed — a small operation that achieves healing in more than 90% of cases and often brings fast pain relief.
Lateral internal sphincterotomy (LIS) is the right choice when:
- Your fissure hasn't healed after one or two Botox injections
- You'd prefer a single, more definitive treatment rather than repeat injections
- The fissure is particularly severe or has been chronic for many years
LIS is a day procedure under general anaesthetic. A small portion of the sphincter is gently divided, permanently lowering the resting pressure. In published series, more than 90% of fissures heal after LIS, and many people notice substantial pain relief within days. Recovery is similar to a haemorrhoidectomy but often a little more comfortable — most people are back to desk work within 1–2 weeks and fully recovered by 3–4 weeks.
Both Botox and surgery address the same underlying problem — the sphincter spasm — just by different routes. Neither treatment removes the need for ongoing dietary measures. Keeping your stools soft, eating enough fibre, staying hydrated, and not straining remain important after any treatment to prevent the fissure coming back.
The injection is done under anaesthesia, so you won't feel it at the time. Afterwards, some people have mild discomfort around the area for 24–48 hours — usually less than the ongoing pain of the fissure itself. For most people, the experience is less unpleasant than anticipated.
Temporary minor leakage of liquid stool or wind is reported in around 2–10 in every 100 people and resolves as the Botox wears off over 3–4 months. Substantial incontinence of solid stool is uncommon. Because the effect is temporary, the continence risk is lower than with surgery.
Most people notice that going to the toilet hurts less within the first 1–2 weeks. Some people feel improvement within 3–5 days. The fissure itself takes longer to fully close — allow 6–12 weeks for the wound to heal completely, though your pain often improves well before the wound has fully healed.
Yes. If the fissure heals but later comes back, a repeat injection is an option. If the first injection doesn't achieve healing, a second injection — sometimes at a higher dose or slightly different site — may be tried before moving to surgery.
In Australia, Botox injection for a chronic anal fissure is a recognised surgical procedure covered by Medicare (a specific item number applies) and claimable through private health insurance for patients with appropriate hospital cover. Out-of-pocket costs depend on your insurer and surgeon's fees. The surgeon's rooms can provide a fee estimate before you book.
Keep taking a daily stool softener (lactulose or macrogol) throughout the period the Botox is active. Maintain a high-fibre diet, drink plenty of water, take warm sitz baths after every bowel motion, and continue any topical ointment your surgeon has recommended. If a stool isn't coming easily, step away from the toilet and try again later — never strain. These steps create the best possible conditions for healing while the Botox is doing its job.
Need a specialist opinion?
If something in this article matches what you're experiencing, the most useful next step is a proper assessment. A GP referral is required.