What prescription drugs treat anal fissures?
Anesthetics and steroids
Topical anesthetics (for example, xylocaine, lidocaine, tetracaine, pramoxine) are recommended especially prior to a bowel movement to reduce the pain of defecation. Often, a small amount of a steroid is combined in the anesthetic cream to reduce inflammation. The use of steroids should be limited to two weeks because longer use will result in thinning of the anoderm (atrophy), which makes it more susceptible to trauma. Oral medications to relax the smooth muscle of the internal sphincter have not been shown to aid healing.
Because of the possibility that spasm of the internal sphincter and reduced flow of blood to the sphincter play roles in the formation and healing of anal fissures, ointments with the muscle relaxant, nitroglycerin (glyceryl trinitrate), have been tried and found to be effective in healing anal fissures. Glycerin trinitrate (nitroglycerin) has been shown to cause relaxation of the internal anal sphincter and to decrease the anal resting pressure. When ointments containing nitroglycerin are applied to the anal canal, the nitroglycerin diffuses across the anoderm and relaxes the internal sphincter and reduces the pressure in the anal canal. This relieves spasm of the muscle and also may increase the flow of blood, both of which promote healing of fissures. Unlike Nitropaste, a 2.0% concentration of nitroglycerin that is used on the skin for patients with heart disease and angina, the nitroglycerin ointment used for treating anal fissures contains a concentration of nitroglycerin of only 0.2%. One randomized, controlled trial has demonstrated the healing of anal fissures in 68% of patients with nitroglycerin as compared to 8% of patients treated with placebo (inactive treatment). Other studies have shown a 33% to 47% recurrence rate of fissures following treatment with nitroglycerin. The presence of a sentinel pile is associated with a lower healing rate with nitroglycerin treatment.
The dose of nitroglycerin often is limited by side effects. The usual side effects are headache (due to dilation of blood vessels in the head) or light-headedness (due to a drop in blood pressure). This author recommends that a small amount of ointment be applied to a cotton-tipped swab with the swab then inserted into the anus only for the depth of the cotton-tipped portion of the swab. Ointment smeared only around the outside of the anus does not reach the anoderm where its effects are important, yet the nitroglycerin will be absorbed and produce side effects.
Nitroglycerin is more rapidly absorbed if blood flow in the anoderm is high. For this reason, it is recommended that nitroglycerin not be applied within 30 minutes of a bath since the warm water of the bath enlarges (dilates) the blood vessels in the skin and anoderm and increases their flow of blood. Additionally, the first application of nitroglycerin should be at bedtime while the patient is lying down in order to prevent falls due to light-headedness.
The side effects of nitroglycerin often are self-limited, that is, they become less with repeated use. Caffeine can help reduce or prevent headaches. However, if side effects are pronounced, nitroglycerin should be discontinued. Drugs for impotence (for example, sildenafil (Viagra), should not be used together with nitroglycerin since they increase the risk of developing low blood pressure.
Calcium channel blocking drugs (CCBs)
As is the case with nitroglycerin, ointments containing calcium channel blocking drugs (for example, nifedipine [Adalat] or diltiazem [Cardizem]) relax the muscles of the internal sphincter. They also expand the blood vessels of the anoderm and increase the flow of blood. Nifedipine ointment (2%) is applied in a manner similar to nitroglycerin ointment, but seems to produce fewer side effects. Although healing of chronic fissures has been reported in up to 67% of patients treated with calcium channel blockers, they are most effective with acute fissures.
Botulinum toxin (Botox) relaxes (actually paralyzes) muscles by preventing the release of acetylcholine from the nerves that normally causes muscle cells to contract. It has been used successfully to treat a variety of disorders in which there is spasm of muscles, including anal fissures. The toxin is injected into the external sphincter, the internal sphincter, the intersphincteric groove (an indentation just inside the anus that demarcates the dividing line between external and internal sphincters), or into the fissure itself. The dose is not standardized and has varied from 2.5 to 20 units of toxin in two locations (usually on either side of the fissure). The cost of a 100-unit vial of toxin is several hundred dollars and unused toxin cannot be saved. Thus, the expense for a single injection of toxin is high. In some series of patients but not all, the frequency of healing of fissures with botulinum toxin is high. When fissures recur after treatment, they usually heal again with a second injection. One representative study found that fissures healed in 87% of patients by six months after treatment with botulinum toxin. By 12 months, however, the healing rate had fallen to 75% and by 42 months to 60%. The primary side effect of botulinum toxin is weakness of the sphincters with varying degrees of incontinence (leakage of stool) that usually is transient. Other side effects are not common.
There is a great variability in the medical literature with respect to the effectiveness of drugs and botulinum toxin in the healing of anal fissures. Healing may be temporary and fissures may return with a hard bowel movement. Recurrent fissures often require a change to another form of treatment. Patients need to balance the effectiveness of treatment, short and long-term side effects, convenience, and expense in choosing their treatment. When patients are intolerant or unresponsive to non-surgical treatments, surgery becomes necessary.