Vitamin D Toxicity - Case Report
Barley, a 1 year old male neutered Labrador, was bored. His owner, Sally Haddock DVM and her husband, had gone out to dinner. Not one to be bored for long, Barley entertained himself by chewing on a tube of medication left out on the coffee table.
When Dr. Haddock returned home and found the chewed remnants of the metal tube, her first concern was metal toxicity or gastrointestinal problems as the metal passed through the intestinal tract. She wasn't too worried about the medication - it was only about 1/3 of a tube and had expired 10 years ago.
The next day Dr. Haddock brought Barley into her clinic, St. Marks Vet, to radiograph his abdomen and check for metal fragments. No fragments or problems seen. That was the good news.
Then she decided to look up the medication, Dovonex, a human medication used for treating psoriasis. When she realized that the active ingredient was calcipotriene, a form of vitamin D, alarm bells went off. This compound is similar to the active ingredient in some rat poisons, and potential for trouble was severe.
Note: In addition to rat poison, other potential sources are: Vitamin D supplements (including over supplementation of pet diets) and human medications for a variety of conditions, including kidney failure, cancer and hypoparathyroidism.
This type of toxicity typically takes some time for clinical signs to appear. While Barley was clinically fine (no symptoms yet), Barley's initial bloodwork showed very high phosphorus levels. This is the first change seen with this type of toxicity, followed by extremely high blood calcium levels. The calcium then calcifies tissues; lungs, gastrointestinal tract, kidneys, heart and more, often leading to death if untreated.
Dr. Haddock began treatment immediately. Barley was hospitalized for 1 month. She consulted with the ASPCA poison control daily during this time, sometimes a few times a day.
Treatment was aimed initially at ridding the body of the toxin using activated charcoal and cholestyramine. Charcoal is a binder and cholestyramine decreases the internal (enterohepatic) recirculation of the vitamin D. This initial decontamination caused bloody diarrhea, abdominal pain, and vomiting for Barley.
Large amounts of intravenous (IV) fluids were given, to flush out excess levels of toxin, phosphorus and calcium. Additional medications, including high doses of prednisone, a cortisone, and Lasix, a diuretic, were given to help flush out the toxins and normalize blood levels.
Despite the aggressive treatment, Barley's calcium levels kept rising, to dangerously high levels.
Next step for Dr. Haddock was to start Pamidronate, a medication used in human medicine, but difficult to obtain. She was able to find a source and the Pamidronate was administered IV over 6 hours. The calcium-lowering effects peak in 3 days.
About 3 weeks into the treatment, Dr. Haddock noticed that Barley was trembling. Fearing that the calcium levels had dropped too low, she ran additional bloodwork.
The pamidronate had worked and the dangerously high calcium levels lowered, but the calcium dropped too low. Low blood calcium, or hypocalcemia is also life-threatening.
To correct the too-low calcium levels, Barley was given some calcium-rich Tums, a very SLOW administration of calcium IV, and decreased dosing of Lasix and prednisone.
While in the hospital on the high doses of IV fluids, Barley had to urinate every 15 minutes and in large volumes. Dr. Haddock stayed with him every night at the hospital, unhooking his IV and taking him outside to relieve his bladder.
Despite the extreme worry caused by this incident, nights of lost sleep, and incredible stress for his people, Barley rebounded back to health after the month-long ordeal, full of his usual zest and vigor. He may be at risk for tissue mineralization in the future - no one knows for sure - but for now, he is now back to his happy, mischievous self. The house once again "puppy proofed" to keep him safe. Barley definitely beat the odds.
Update from Dr. Haddock: Radiographs taken 1 month later showed no mineralization of the lungs or internal organs.
Here's to many happy healthy years ahead for Barley.
More: Meet Barley (photos)