Zinc supplements (zinc sulphate) should only be given when there is good evidence of zinc deficiency or in zinc-losing conditions.¹ Zinc supplements must be used with caution in view of the dangers of zinc excess and zinc toxicity.

Indications for supplements

• Zinc deficiency and zinc-losing conditions, e.g. following trauma, burns and other protein-losing conditions, e.g. protein-losing enteropathy.
• Zinc acetate is used to treat Wilson's disease.
  Studies have also reported its use to enhance wound healing and slow macular degeneration.
• Zinc has also been claimed to ameliorate a variety of conditions including the common cold. The effect of zinc treatments on the severity or duration of cold symptoms is controversial and unproven.²
• A zinc supplement is given until clinical improvement occurs but it may need to be continued in severe malabsorption, metabolic disease or in zinc-losing states.
• Total parenteral nutrition regimens usually include trace amounts of zinc. If necessary, further zinc can be added to intravenous feeding regimens.

Dosage¹

Effervescent zinc sulphate tablets contain 125 mg of zinc sulphate (45 mg zinc):

• Adult and child over 30 kg, 1 tablet in water 1-3 times daily after food.
• Child under 10 kg, ½ tablet daily.
• Child 10-30 kg, ½ tablet 1-3 times daily.

Cautions

• May accumulate in acute renal failure.
• A small study has suggested that zinc supplementation increases the levels of glycosylated haemoglobin in diabetics.
• Sufferers from haemochromatosis may absorb larger amounts of zinc.

Interactions

• Zinc and copper are mutually antagonistic, each interfering with the gastrointestinal uptake of the other.
• Excess zinc may also decrease magnesium and calcium uptake. High levels of calcium in the diet can decrease zinc absorption.
• Zinc salts reduce the bioavailability of fluoroquinolone antibiotics, e.g. ciprofloxacin.
• Absorption of zinc is reduced by penicillamine and zinc also reduces the absorption of penicillamine.
• Absorption of zinc is reduced by tetracyclines and zinc also reduces the absorption of tetracyclines.

Side-effects

• Zinc supplements have been reported to cause gastrointestinal effects, including abdominal pain, dyspepsia, nausea, vomiting, diarrhoea, gastric irritation, and gastritis. This is more likely when supplements are taken with little or no food.
• Irritability, headache, lethargy, dizziness.
• Prolonged use of high doses of zinc can result in deficiency of copper.
• It has been suggested but not proven that excess zinc is atherogenic.²

Document references

1. British National Formulary
2. Food Standards Agency; Zinc

Acknowledgements