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Capsule Entrapment

Sandra Justice, P.D., FACA

Many pets receive medication in the form of oral capsules or tablets. In people, tablets and capsules can take a long time to pass through the esophagus into the stomach. Sometimes tablets and capsules dissolve in the esophagus before they reach the stomach. Occasionally, these medication forms become entrapped in the esophagus and expose the mucous membranes located there to a high concentration of a medication for a prolonged time. When this happens, many medications can be ulcerogenic, in other words, they can burn a hole in the mucous membranes of the gastrointestinal tract.

While studies have shown that capsules and tablets can become entrapped in the human esophagus, little attention has been paid to the effects of capsules given orally to pets. Theoretically, cats and dogs should have an even greater risk from entrapped capsules or tablets, since they do not have an upright posture in which gravity will assist the medication in moving towards the stomach. Additionally, cats and dogs do not drink water to assist with swallowing medication. A recent study was conducted in cats to determine whether entrapment of orally administered capsules was a problem. Cats were given oral capsules on three different occasions and then examined with fluoroscopy to see what happened to the capsules. Nearly 53 percent of the orally administered capsules became trapped in the esophagus. In 56 percent of the cats, at least one of the administered capsules never reached the stomach. In 33 percent of the cats, none of the 3 administered capsules ever reached the stomach. In cats experiencing entrapment, a small amount (0.5-1 oz) of food was given. This dislodged the trapped capsule and allowed safe passage into the stomach.

Often the volume of a tablet or a capsule alone cannot stimulate enough muscular activity in the esophagus to completely carry the dosage form to the stomach. Studies in humans have proven that drinking water with medications will provide enough volume to activate these muscles. Because cats cannot be made to drink when medications are administered, they are much more likely to suffer injury from capsule entrapment. Studies also support the theory that capsules are more likely to get stuck in the esophagus than tablets. This is because gelatin, the substance capsules are made of becomes tacky when it comes in contact with the moisture of mucous membranes like the esophagus, causing the capsule to adhere. Lubricating the outside of these capsules with oils or other slippery substances has been shown to prevent capsule entrapment in humans.

Virtually all human-labeled drugs must be reformulated for appropriate doses in smaller animals. As many drugs are not stable in a liquid dosage form, capsules are often the only dosage form option for cats. Based upon results of studies in humans and incidental reports of injury from capsules in pets, it is highly recommended that the following steps be taken to prevent injury to your dog or cat when they are given medication in capsule form:

  • Have your veterinarian instruct the pharmacist to compound   medications for your pet in the smallest available capsule size, preferably   size 4 or smaller.
  • Give one-half to one ounce of food immediately following oral   administration of tablets or capsules. For medications that must be given   on an empty stomach, give small amounts of water to the animal to   facilitate passage of the drug into the stomach.
  • Elevate the head and neck during and immediately following   administration of a tablet or capsule.
  • Lubricate capsules with a small amount of corn oil or butter to prevent   adherence to the mucous membrane of the esophagus.

By following these recommendations when administering solid oral dosage forms to pets you should be able to prevent drug erosion-related injuries. In the event that any dosage form presents problems for administration, you may wish to consult with your veterinarian and compounding pharmacist who can assist you in selecting the most appropriate dosage form for your pet.