Cisapride is a motility drug used in cats primarily to treat chronic constipation and megacolon. It works by stimulating the muscles of the digestive tract to push contents forward, making it one of the most commonly prescribed medications for cats whose colons have lost the ability to move stool effectively on their own. It’s also used for certain upper digestive problems like acid reflux and megaesophagus.
How Cisapride Works
Cisapride targets serotonin receptors on the nerve cells that control the smooth muscle lining the digestive tract. When the drug activates these receptors, the nerves release acetylcholine, a chemical messenger that causes the muscle to contract. The result is stronger, more coordinated waves of movement from the lower esophageal sphincter all the way down to the colon. This is why cisapride is effective for problems at multiple points along the digestive tract, not just constipation.
Megacolon and Chronic Constipation
The most common reason a veterinarian prescribes cisapride for a cat is megacolon, a condition where the colon becomes severely stretched and loses its ability to contract. Cats with megacolon produce hard, dry stool that accumulates in an increasingly distended colon, leading to painful and infrequent bowel movements. Over time, the colon wall weakens further, creating a cycle that’s difficult to break without medication.
Cisapride helps by restoring some of the colon’s ability to push stool forward. For cats with idiopathic constipation (chronic constipation with no identifiable structural cause), cisapride is typically used alongside dietary changes like increased fiber or hydration support. The goal is to keep the cat passing stool regularly enough to prevent the colon from stretching further. In early to moderate cases, cisapride can be very effective. In advanced megacolon where the colon wall has already been irreversibly damaged, surgery to remove part of the colon may eventually become necessary.
Upper Digestive Tract Uses
Because cisapride strengthens muscle contraction throughout the entire digestive tract, it has applications beyond constipation. It increases pressure at the lower esophageal sphincter, which helps prevent stomach acid from flowing backward into the esophagus. This makes it useful for cats with gastroesophageal reflux, particularly those recovering from anesthesia or dealing with chronic reflux issues.
Cisapride has also been found helpful in some cases of megaesophagus, a condition where the esophagus loses tone and becomes dilated, causing food to sit in the esophagus rather than moving into the stomach. Additionally, because the drug promotes stomach emptying, it can reduce nausea caused by food sitting too long in the stomach. It does not, however, act on the brain’s nausea center the way some other anti-nausea drugs do.
Less Common Uses
Because cisapride affects smooth muscle contraction generally, veterinarians occasionally use it to help cats with urinary retention, where the bladder isn’t contracting strongly enough to empty fully. This application is uncommon but reflects the drug’s broad effect on smooth muscle throughout the body.
Side Effects
Most cats tolerate cisapride well. When side effects do occur, they’re usually mild: vomiting, diarrhea, or general stomach discomfort. These often resolve on their own or with a dose adjustment.
More concerning signs include drooling, incoordination, muscle twitches, agitation, unusual behavior, elevated body temperature, or seizures. These reactions typically indicate the dose is too high and warrant prompt veterinary attention. Cisapride should not be given to cats with a known gastrointestinal obstruction or perforation, since stimulating the gut to contract against a blockage can cause serious harm.
Drug Interactions to Know About
Cisapride is broken down in the body by a specific liver enzyme. Several common medications block that same enzyme, which can cause cisapride to build up to dangerously high levels in the bloodstream. The most relevant ones for cat owners to be aware of include certain antifungal medications (ketoconazole, itraconazole, fluconazole) and specific antibiotics like erythromycin and clarithromycin. The acid-reducing drug cimetidine also interferes with cisapride metabolism, though alternatives like famotidine do not. If your cat is on any other medications, your veterinarian will check for interactions before adding cisapride.
Dosing and Administration
Cisapride is given by mouth, typically every 8 to 12 hours. For cats with idiopathic constipation, a common starting dose is 2.5 mg two to three times daily, though your veterinarian will adjust this based on your cat’s weight and response. Some cats need the drug long-term, while others use it for a defined period alongside other interventions like diet changes or laxatives.
Why You Need a Compounding Pharmacy
Cisapride was pulled from the U.S. human market in 2000 due to cardiac side effects in people. It is no longer commercially manufactured in standard tablet form. For veterinary use, it must be obtained through a compounding pharmacy, which creates custom preparations based on a veterinarian’s prescription. Compounding pharmacies typically offer cisapride as flavored liquids, capsules, or chewable treats, which makes dosing easier for cat owners. Your veterinarian will write the prescription and can usually direct you to a pharmacy experienced in preparing it.