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PHARMACOLOGICAL ACTIVITIES - TOXICOLOGY - DRUG INTERACTIONS

Zinc (Citrate)

Zinc plays important roles in growth and development, the immune response, neurological
function, and reproduction. On the cellular level, the function of zinc can be divided into three
categories: catalytic, structural, and regulatory (Bowman & Russell, 2006). Inadequate zinc
supply, especially in growing animals, may lead to severe clinical signs within days, resulting in
growth depression, skin defects, impaired immune function, and growth disorders of the skeleton
(Ettinger & Feldman, 2000a). Zinc deficiency in the dog most commonly occurs as a skin
condition called ‘zinc responsive dermatosis’ (Colombini, 1999; Campbell & Crow, 2010). The
usual symptoms are hair loss, and scaling and crusting of the skin around the face, head, and legs.
Lesions often encircle the mouth, chin, eyes, and ears. The foot pads may be scaly and the hair
coats are dull and dry.

Toxicity for zinc has not been documented in dogs and cats when administered orally in therapeutic doses.
However, zinc toxicosis caused by ingestion of foreign materials such as galvanized metal and pennies has been
TOXICOLOGY reported in dogs, but it has not been described in cats (Hardy et al., 2003). No evidence of significant pathological

effects were observed in rats following daily oral administration of zinc (as zinc citrate, zinc acetate, zinc oxide
or zinc maleate) in doses up to 34 mg/kg of body weight for 35 to 53 weeks. Oral LD for zinc chloride is 350
50
mg/kg of body weight in rats and mice, 200-250 mg/kg of body weight in rabbits. Oral LD for zinc sulphate is
50
2,200 mg/kg of body weight in rats and 2,100 mg/kg of body weight in rabbits (EMEA, 1996).

DRUG Both quinolone antibiotics and tetracycline antibiotics interact with zinc in the gastrointestinal tract,
INTERACTIONS inhibiting the absorption of both zinc and the antibiotic (Lomaestro et al., 1995; Penttilä et al.,
1975). Zinc can reduce the absorption and action of penicillamine, a drug used to treat rheumatoid
arthritis (Brewer et al. 1993). Thiazide diuretics such as chlorthalidone and hydrochlorothiazide
increase urinary zinc excretion by as much as 60% (Wester, 1980).

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