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# Zinc
## Overview
Zinc is an essential trace element required for protein synthesis, wound healing, immune function, and enzymatic processes. It acts as a cofactor for over 300 enzymes.
## Primary Indications
* Treatment and prevention of zinc deficiency (e.g., malabsorption, prolonged parenteral nutrition).
* Adjunct in severe diarrhea (WHO protocol).
* Wound healing (limited evidence).
## Adult Dosing
* **Maintenance:** 8 mg (females) to 11 mg (males) elemental zinc daily.
* **Deficiency:** 25–50 mg elemental zinc daily, divided into 1–3 doses.
* **Note:** Dosing varies significantly by salt form (e.g., Zinc Gluconate, Zinc Sulfate, Zinc Acetate). Always calculate based on *elemental* zinc content. For example, 220 mg Zinc Sulfate heptahydrate contains approximately 50 mg elemental zinc.
## Pediatric Dosing
* **Maintenance (RDA):** 0–6 months (2 mg), 7–12 months (3 mg), 1–3 years (3 mg), 4–8 years (5 mg), 9–13 years (8 mg).
* **Diarrhea (WHO/UNICEF):** 10 mg (infants <6 months) or 20 mg (children >6 months) elemental zinc daily for 10–14 days.
* **Acrodermatitis Enteropathica:** 30–150 mg elemental zinc daily, titrated based on clinical response and plasma zinc levels.
## Dose Adjustments
* **Renal Impairment:** No standard adjustment required, but monitor for accumulation in end-stage renal disease.
* **Hepatic Impairment:** Use caution; zinc is excreted primarily via biliary/fecal routes.
## Contraindications
* Hypersensitivity to zinc salts.
* Patients with copper deficiency (high-dose zinc induces copper deficiency).
## Adverse Effects
* **Common:** GI distress (nausea, vomiting, diarrhea, abdominal cramps).
* **Chronic/High Dose:** Copper deficiency leading to sideroblastic anemia and neutropenia, impaired immune function, decreased HDL cholesterol.
## Key Drug Interactions
* **Fluoroquinolones/Tetracyclines:** Zinc forms insoluble chelates with these antibiotics, significantly reducing absorption. Separate administration by at least 2–4 hours.
* **Copper:** Long-term zinc supplementation competes for intestinal absorption, potentially inducing copper deficiency.
* **Iron:** High doses of supplemental iron can inhibit zinc absorption.
## Monitoring
* Serum zinc levels (though often poorly representative of total body stores).
* Monitor copper levels during long-term high-dose therapy.
* Hemoglobin/Hematocrit (for signs of copper-deficiency anemia).
## Clinical Pearls
* **Absorption:** Bioavailability is superior when taken with meals to minimize GI irritation, though phytates (in grains/legumes) may decrease absorption.
* **Formulation:** Always verify the "elemental" content. Labels often list the weight of the salt (e.g., Zinc Sulfate 220 mg) rather than the elemental zinc (50 mg).
* **Uncertainty:** There is no universally agreed-upon "exact" dose for therapeutic supplementation in diverse clinical states without specific laboratory deficiencies; consult institutional nutrition support guidelines.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice varies based on institutional protocols and patient-specific factors. Always verify specific dosing, salt forms, and contraindications by consulting current FDA-approved labeling, the package insert, or a reliable clinical database (e.g., UpToDate, Lexicomp) before prescribing or administering medication.
