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# Zinc
## Overview
Zinc is an essential trace element required for protein synthesis, immune function, wound healing, and DNA synthesis. It acts as a cofactor for over 300 enzymes. Elemental zinc content varies significantly between salt forms (e.g., zinc gluconate ~14%, zinc sulfate ~23%, zinc acetate ~30%).
## Primary Indications
* Treatment/prevention of zinc deficiency (malabsorption, TPN-associated, dietary inadequacy).
* Adjunct therapy for Wilson’s disease.
* Short-term reduction of common cold duration (lozenges only).
## Adult Dosing
* **Dietary Supplementation:** 15–50 mg elemental zinc daily.
* **Zinc Deficiency:** 50–100 mg elemental zinc daily (in divided doses).
* **Wilson’s Disease:** 50 mg elemental zinc three times daily (maintenance).
* **Common Cold:** 75 mg elemental zinc per day (started within 24 hours of symptom onset; limited by toxicity risk/tolerability).
* **Maximum:** Tolerable Upper Intake Level (UL) is 40 mg of elemental zinc daily for chronic use. Higher doses require medical supervision.
## Pediatric Dosing
* **Supplementation:** Based on RDA (approx. 2 mg/day for infants to 11 mg/day for adolescents).
* **Acute Diarrhea (WHO/UNICEF guidelines):** 10 mg elemental zinc daily for infants <6 months; 20 mg elemental zinc daily for children ≥6 months for 10–14 days.
* **Maximum:** UL based on age (e.g., 5 mg for infants, 7 mg for toddlers, 23 mg for teenagers).
## Dose Adjustments
* **Renal Impairment:** No specific adjustment; maintain close monitoring for serum accumulation if long-term high-dose therapy is used.
* **Hepatic Impairment:** No specific adjustment.
* **Malabsorption:** Doses may need adjustment based on clinical response and serum zinc levels.
## Contraindications
* Hypersensitivity to zinc salts.
## Adverse Effects
* **Common:** Epigastric pain, nausea, vomiting, diarrhea, metallic taste.
* **Serious (Chronic High-Dose):** Copper deficiency (manifesting as anemia or neutropenia), sideroblastic anemia, neurological impairment.
## Key Drug Interactions
* **Antibiotics:** Zinc impairs the absorption of tetracyclines and fluoroquinolones. Separate administration by at least 2–4 hours.
* **Penicillamine:** Zinc and penicillamine reduce each other's absorption.
* **Copper:** High-dose zinc induces intestinal metallothionein, which traps copper and prevents its absorption, potentially leading to copper deficiency.
## Monitoring
* **Long-term high-dose therapy:** Monitor serum zinc levels, copper levels, and ceruloplasmin levels.
* **Hematology:** Monitor CBC for signs of copper deficiency-induced anemia or neutropenia.
## Clinical Pearls
* **Absorption:** Best absorbed on an empty stomach, but gastrointestinal upset often necessitates administration with food.
* **Salt Form:** Always verify the "elemental" content versus the "salt" weight (e.g., 220 mg of zinc sulfate heptahydrate contains 50 mg of elemental zinc).
* **Copper Depletion:** If zinc supplementation exceeds 50 mg/day for more than a few weeks, consider prophylactic copper supplementation (approx. 2 mg/day) to prevent deficiency.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical dosing and indications may vary based on local guidelines, comorbidities, and specific formulation salt weights. Always verify current prescribing information, institutional protocols, and patient-specific factors before administration.
