446 TOXICOLOGY BRIEF Veterinary Technician July 2006 Ingestion of Over-the-Counter CALCIUM SUPPLEMENTS

Katrina L. McKnight, CVT, BS Although tempting to dogs, ASPCA Animal Poison Control Center calcium supplements can be Urbana, Illinois toxic in large quantities.

The clinic phone rings, and Ms. Miller, a concerned dog owner, is lematic because calcium salts are on the line. Her English cocker spaniel, Buttons, has just eaten a poorly absorbed from the gastrointesti- nal (GI) tract. A transient increase in whole box of her calcium supplement chews. Buttons ingested every serum calcium may occur but rarely chew — wrappers and all! The dog seems to be fine, but Ms. Miller requires medical intervention. Of much is seeking medical advice. greater concern is the vitamin D3 com- ponent. Vitamin D3 can be more toxic to the patient because it increases the The staff veterinarians and techni- obstruction. Some chews are chocolate serum calcium level by increasing the cians at the ASPCA Animal Poison Con- flavored, but the amount of actual absorption of calcium from the GI tract, trol Center (APCC) are frequently chocolate present is minimal and not decreasing the elimination of calcium consulted on cases of calcium supple- enough to cause clinical signs in pets.1–4 by the kidneys, and increasing the ment ingestion. Although these supple- resorption of calcium from the bones.1,5 ments come in various forms, one of the MECHANISM OF ACTION most commonly involved in pet expo- In cases of calcium supplement over- RISK FACTORS sures is nonprescription calcium chews, dose, the calcium is usually not prob- In most cases, calcium chews do not which come in many different flavors that can attract an animal’s attention. Common Calcium Supplements

EXPOSURE AND SUSCEPTIBILITY Vitamin D3 Calcium Vitamin K Most over-the-counter calcium sup- Supplement Content (IU) Content (mg) Content (µg) plements include vitamins D3 (cholecal- AVON VitAdvance 200 650 — ciferol) and K to help maximize Soft Calcium Chew calcium absorption. The calcium and Caltrate 600+D Calcium 200 600 — vitamin D3 in the chews have the Dietary Supplement Tablet potential to elevate serum calcium and phosphorus levels. Vitamin K has a CVS Soft Calcium Chew 100 500 40 wide margin of safety and is present LA Weight Loss Milk 200 500 — only in small amounts in calcium sup- Chocolate Calcium Chew plements. Ingestion of a large quantity Viactiv Soft Calcium Chew 100 500 40 of chew wrappers may lead to intestinal

Toxicology Brief is contributed by veterinary technicians at the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center, 1717 S. Philo Rd., Suite 36, Urbana, IL 61802; hotline: 888-426-4435 (a $55 consultation fee is charged to the caller’s telephone bill) or 900-443-0000 (a $60 fee is charged); email: [email protected] (for nonemergency information only); Web site: www.apcc.aspca.org. Veterinary Technician July 2006 INGESTION OF CALCIUM SUPPLEMENTS 447

contain enough absorbable calcium to be considered life threatening to pets. How Much Vitamin D3 Did Buttons Ingest? However, very young animals and animals with preexisting renal dis- To calculate the amount of vitamin D3 (cholecalciferol) Buttons ingested, the ease may be more sensitive to the veterinary technician made the following assessments: calcium and are at greater risk for • Weight: According to Ms. Miller, Buttons weighs 30 lb. To obtain the dog’s toxicosis.1,3–5 weight in kilograms, the technician divided 30 by 2.2, which equals 13.63 kg. According to the APCC, vita- min D doses below 0.1 mg/kg • Number of chews eaten: Based on the number of wrappers found in the 3 dog’s vomit, Buttons ate 40 chews. can cause mild, self-limiting GI upset in a healthy animal. Doses • Amount of D3 in one chew (in International Units): According to the product of 0.1 mg/kg or greater can cause label, each chew contains 400 IU of vitamin D3. hypercalcemia, which may lead to • Amount of D3 in one chew (in milligrams): 1 IU = 0.000025 mg of D3. acute renal failure, but this dose is Therefore, one chew contains 0.000025 mg × 400 IU = 0.01 mg of vitamin D3. rarely reached with ingestion of cal- • Total amount of D3 Buttons consumed: 0.01 mg × 40 chews = 0.4 mg of D3. 1,2,4 cium supplements. • Total dose of D3 Buttons consumed: 0.4 mg ÷ 13.63 kg = 0.029 mg/kg. The product label of calcium chews usually indicates the amount of vita- Luckily for Buttons, the D3 dose of 0.029 mg/kg is well below the 0.1 mg/kg min D3 in International Units (IU), so dose of concern. the first step in assessing an overdose situation is to convert IU to milli- grams. For vitamin D3, 1 IU = 0.025 µg hypercalcemia, and hypoadrenocorti- the severity of the condition will affect or 0.000025 mg.4 cism, should be ruled out. the extent of treatment as well as the outcome. In cases in which renal CLINICAL SIGNS TREATMENT effects worsen and lead to a loss of Acute ingestion of calcium salts Management of a patient with cal- renal function, the prognosis is poor.7 from calcium chews may cause vomit- cium or vitamin D3 toxicosis depends ing, diarrhea, GI irritation, and, possi- on the dosage ingested and the sever- ROLE OF THE TECHNICIAN bly, transient hypercalcemia.1,6 Signs of ity of the signs. As noted above, tran- Many cases of calcium supplement hypercalcemia include azotemia, sient hypercalcemia may occur in ingestion begin as a phone call in twitching, nausea, abdominal pain, some cases but rarely requires treat- which the patient needs to be assessed tachypnea, hematuria, melena, dehy- ment.1,6 Because some animals also for risk. Veterinary technicians can dration, and electrocardiographic ingest calcium chew wrappers, which assist with dose calculations and share changes.7,8 Acute exposure to calcium may ball up and obstruct the GI tract, information with the veterinarian. supplements should not result in soft initial emesis in clinically normal Often, initial decontamination is per- tissue calcification.1 patients may be of benefit. Activated formed at home by a pet owner who is

Clinical signs of vitamin D3 toxicosis charcoal does not bind to calcium following the instructions of a veteri- may include anorexia, depression, vom- salts, so it should be given only if the nary technician. iting, polydipsia, polyuria, and serum dose of vitamin D3 is of concern. Although the veterinarian is the one chemistry changes (elevated blood urea Often, treatment includes fluid ther- who determines the full treatment w nitrogen, serum creatinine, calcium, and apy using 0.9% saline, serum chem- plan, basic symptomatic care and good w phosphorus). Lethargy and weakness istry monitoring, and the use of GI nursing care by the veterinary techni- w . may also be seen. protectants. Acute renal failure may be cian will help achieve a positive out- V treated with furosemide and dopamine. come for these patients.1,4,7,8 e t

DIAGNOSIS Symptomatic and supportive care T The history of exposure, clinical signs should be given as needed. * * * e c

present, and serum chemistry findings In Buttons’ case, the veterinary tech- h must be determined when diagnosing PROGNOSIS nician instructed Ms. Miller to induce J o

calcium or vitamin D3 toxicosis. If the The prognosis for patients that have vomiting and to count the number of u patient has ingested more than 0.1 ingested calcium chews depends on wrappers in the vomit. The technician r mg/kg of vitamin D , it is important to many factors. In most cases, a positive then calculated the dose according to n 3 a monitor renal values, including serum outcome may be expected if the expo- the estimated number of chews the dog l . calcium and phosphorus. Other causes sure is caught early and signs are ingested. Based on the dose and emesis c of hypercalcemia, such as normal juve- recognized and controlled. If hypercal- results, no further action was war- o m nile hypercalcemia, cancer-associated cemia or acute renal failure is present, ranted. After giving Ms. Miller instruc- (continues on page 451) www.VetTechJournal.com - - T V 451 . eterson M (ed): Philadelphia, Kirk’s Current ed 5. Ames, Iowa State Bonagura JD (eds): , (continued from page 447) eterinary Drug Handbook, Thomson Micromedex. Updated periodically V , xicosis, in Kirk RW 1998–2005. Village, CO wood Village, CO, Thomson Micromedex. Updated periodically. Updated periodically. Thomson Micromedex. wood Village, CO, assays in the evaluation of hypercalcemia and hypocalcemia: parathyroid hor- hormone, vitamin D metabolites, Parathyroid mone-related peptide, and ionized calcium, in P Philadelphia, WB Saunders, 1995, pp 378–383. lished data, Urbana, IL, 2003. Plumb DC: Kirk’s Current Veterinary Therapy XII: Small Animal Practice. Kirk’s Current Veterinary ciferol to University Press, 2005, pp 109–112, 635. University Press, 2005, pp 109–112, Dorman DC, Beasley VR: Diagnosis and therapy for cholecal Veterinary Therapy X: Small Animal Practice. Veterinary WB Saunders, 1989, pp 148–152. periodically. Thomson Micromedex. Updated Village, CO, Calcium Supplements emesis, the techni tions to withhold food for an hour after ACKNOWLEDGMENT for MS, PhD, DABVT, The author thanks Safdar A. Khan, DVM, reviewing the column and providing suggestions. REFERENCES 1. ASPCA APCC Case Database: Unpublished data, Urbana, IL, 2. System [Internet database]. Greenwood Vitamin K, in Poisindex cian felt that no further care was needed. The next day, Ms. The next day, cian felt that no further care was needed. had any problems Miller called to say that Buttons never help. and that she was grateful for the clinic’s 3. System [Internet database]. Green- in Poisindex Calcium salts, 4. et al: Utility of diagnostic Chew DJ, Nagode LA, Rosol TJ, 5. Gwaltney S: ASPCA APCC Cholecalciferol protocol. Unpub- 6. 7. 8. Greenwood System [Internet database]. Vitamin D, in Poisindex TECH TIPS July 2006 Veterinary Technician Veterinary