Page 412 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Toxicity of Over-the-Counter Drugs Chapter | 21 379

VetBooks.ir TABLE 21.4 An Incomplete List of Mineral Antacids TABLE 21.5 Irritant Cathartics

Aluminum Salts
Diphenylmethanes
Aluminum hydroxide Phenolphthalein
Aluminum magnesium silicate Bisacodyl
Aluminum phosphate Vegetable Oils
Magnesium Salts Castor oil
Magnesium hydroxide Raw linseed oil
Magnesium oxide Olive oil
Magnesium silicate Anthraquinones
Others Cascara sagrada
Calcium carbonate Senna
Sodium bicarbonate Aloin

acid, and this reaction may cause gastric distension (Boothe, products cause fluid and electrolyte loss secondary to
2001). Chronic use of calcium carbonate antacids can pro- diarrhea. Papich (1990) suggests that subsequent dehydra-
duce metabolic acidosis, hypercalcemia, hypophosphatemia, tion can lead to intestinal impaction. Animals treated with
and calciuria with urolithiasis and metastatic calcification bulk-forming laxatives should have fresh water available.
(Fitzgibbons and Snoey, 1999; Boothe, 2001). If diarrhea occurs, monitor hydration and electrolyte sta-
Some of the magnesium in magnesium salt-containing tus and correct as needed.
antacids are absorbed, and hypermagnesemia has been
reported with repeated dosing (Boothe, 2001). Magnesium- Lubricant Laxatives
containing salts have a laxative effect, and aluminum-
Lubricant laxatives, including mineral oil and white petro-
containing salts have a constipating effect, and these active
latum, are hydrocarbon mixtures derived from petroleum.
ingredients are often used in combination. Aluminum com-
Mineral oil is frequently used in large animals, and white
plexes phosphate in the intestine and aluminum hydroxide
petrolatum products are used to treat trichobezoars in cats
has been used to decrease phosphate absorption in patients
(Papich, 1990). These large hydrocarbons are minimally
with renal disease (Segev et al., 2008).
absorbed, and act by coating feces with a film that entraps
moisture and lubricates the passage. Hydrocarbon laxa-
Laxatives, Cathartics and Enemas tives reduce absorption of fat-soluble vitamins and possi-
bly other nutrients; thus, chronic use can produce
Drugs in this category are designated as bulk-forming deficiencies. The small amount of absorbed hydrocarbons
laxatives, lubricant laxatives, irritant laxatives, hyperos- can provide a nidus for granuloma formation in the intes-
motic cathartics, or enemas. tinal mucosa, mesenteric lymph nodes, or liver. Adverse
effects, however, are rarely reported with lubricant
laxatives.
Bulk-Forming Laxatives
Nonabsorbable polysaccharide cellulose derivatives are
used as bulk-forming laxatives. Natural sources include Irritant Laxatives
psyllium or plantago seed, wheat bran, and fruits such as Table 21.5 lists common types of irritant laxative.
prunes. Synthetic forms include methylcellulose and Phenolphthalein laxatives are often chocolate flavored to
carboxymethylcellulose. These products act by absorbing increase palatability, but are reportedly only effective in
water in the gastrointestinal tract, swelling, and softening primates and swine (Boothe, 2001). Bisacodyl is structur-
fecal mass, resulting in intestinal distension and reflex ally similar to phenolphthalein. Some vegetable oil pro-
peristaltic contractions. Intestinal bacteria act on cellulose ducts contain irritant fatty acids such as ricinoleic acid in
and hemicellulose, and produce volatile fatty acids, castor oil, linoleates in linseed oil, and oliveates in olive
enhancing the osmotic effect; fluid feces and tympany oil. Common anthraquinone-type cathartics are derived
can result (Boothe, 2001). No serious adverse effects have from plants: cascara sagrada from Rhamnus spp., senna
been reported in companion animals, although these from Senna spp., and aloin from Aloe spp. Danthron