Generic Name

Zinc

Mechanism

Zinc is a divalent trace metal that acts as an essential cofactor in >300 enzymatic reactions and numerous regulatory proteins.
• Enzyme catalysis – stabilizes protein structures (e.g., DNA‑ and RNA‑dependent phosphodiesterases) and activates key metabolic enzymes (e.g., alkaline phosphatase, carbonic anhydrase).
• Antioxidant defense – functions in the superoxide dismutase (Cu/Zn‑SOD) complex, mitigating oxidative stress.
• Immune modulation –
• Supports thymic development of T‑cells.
• Enhances phagocytic activity of macrophages and neutrophils.
• Limits cytokine over‑production (IL‑1, IL‑6, TNF‑α).
• Antiviral and antibacterial effects – interferes with viral RNA replication and bacterial cell‑surface adhesion.
• Mucosal integrity – maintains epithelial cell turnover; promotes wound healing via keratinocyte proliferation.

Pharmacokinetics

• Absorption – occurs predominantly in the small intestine (jejunum) via ZIP4 transporters; absorbed well in the fasting state (<25 µmol ml⁻¹). Co‑administration with calcium, iron, or high‑phosphate meals ↓ absorption.
• Distribution – 70‑80% protein‑bound (mainly to albumin, α‑1‑acid glycoprotein). Penetrates mucosal tissues and blood‑brain barrier.
• Metabolism – not extensively metabolized; remains mainly bound to proteins.
• Excretion – slow, primarily fecal (≈90 %) with a small renal fraction (≈10 %).
• Half‑life – ≈18 h; steady‑state achieved after ~2 weeks of therapy.

Indications

• Zinc deficiency (e.g., hereditary acrodermatitis, Kwashiorkor, copper deficiency, chronic alcoholism).
• Common cold – zinc acetate or gluconate lozenges (≥9 mg elemental zinc) reduce duration by ~1 day if started within 24 h.
• Acute infantile diarrhea – oral zinc 20 mg/day (age < 6 mo) to 30 mg/day (6 – 12 mo) shortens course and reduces stool volume.
• Wound healing & skin ulcers – topical zinc oxide or zinc pyrithione formulations.
• Dermatologic conditions – psoriasis, atopic dermatitis, acne (topical) and nail dystrophy.
• Nutrition supplementation – pregnant, lactating, pre‑term infants, vegetarians, and the elderly.

Contraindications

• Hypersensitivity to zinc salts.
• Wilson disease – avoid high‑dose oral zinc (not used for copper chelation).
• High baseline serum zinc (e.g., occupational exposure) – risk of hyper‑zincemia and copper deficiency.
• Copper deficiency – chronic high‑dose zinc (≥50 mg elemental daily > 3 months) can precipitate anemia and neutropenia.
• Pregnancy/early lactation – safe up to 25 mg elemental daily; avoid >30 mg/day.
• Drug interactions – inhibits absorption of tetracyclines, fluoroquinolones, penicillins, and sulfonamides; chelate with phytates (e.g., soy, bran).

Dosing

• Administration tip: Administer zinc on an empty stomach or at least 1 hour before/after other medications to maximize absorption.

Adverse Effects

• Common
• Gastro‑intestinal upset (nausea, vomiting, diarrhea, metallic taste, abdominal cramps).
• Taste alteration; long‑term use → dysgeusia.
• Serious
• Copper deficiency → anemia, neutropenia, neuro‑pseudotuberculosis.
• Acute toxicity (dose > 3 g elemental) – vomitus, abdominal cramps, seizures, arrhythmias, hepatic hepatolysis.
• Hypersensitivity (rash, urticaria).
• Monitoring – Watch for hematologic changes if long‑term use >3 months.

Monitoring

• Serum zinc – baseline and after 6–8 weeks if on chronic therapy.
• Serum copper – once every 6 months for those on >2 months of high-dose zinc.
• CBC – baseline and periodical (3–6 mo) to detect anemia or neutropenia.
• Liver function tests – for patients with chronic liver disease or on high‑dose therapy.
• Pregnancy – serum zinc and copper if supplementation >15 mg/day.

Clinical Pearls

• Take it on an empty stomach – improves absorption by 20‑30 %.
• Start lozenges early – must begin within 24 h of cold onset for benefit.
• Chewing zinc lozenges before swallowing – prolongs contact time with the upper airway epithelium, maximizing antiviral effect.
• Avoid high‑calcium meals – calcium competes for ZIP4 transporters; give zinc 2 hrs before or after calcium‑rich foods.
• Topical zinc oxide = barrier and anti‑irritant – essential in diaper dermatitis and periorificial skin.
• Volume of intake matters – overall fluid cup intake >2 L daily improves oral bioavailability of zinc.
• Check for copper deficiency – long‑term zinc therapy >50 mg/day in elderly and those with malabsorption can lead to copper deficiency; consider periodic copper supplementation.
• Drug interaction window – separate tetracyclines and fluoroquinolones by 2 hrs from zinc dosing.
• Zinc and egg yolks – large amounts of phytic acid in the yolk can impair absorption; initiating therapy after a high‑phytic meal reduces effect.

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• *Note: All dosing recommendations reflect current guidelines as of June 2024 and are subject to local regulatory and institutional policies.