High levels of dietary calcium impair zinc absorption in animals, but it is uncertain whether this occurs in humans — separate doses by 2 hours.
CAPTOPRIL AND ENALOPRIL
These drugs increase urinary excretion of zinc. Monitor for signs and symptoms of zinc deficiency. Increased zinc intake may be required with long-term drug treatment.
Coffee reduces zinc absorption — separate intakes by 2 hours.
High zinc intakes (100-1 50 mg/day) interfere with copper metabolism and can cause hypocuprinaemia with long-term use. Avoid using high-dose zinc supplements long term, or increase intake of copper.
Folate intake may reduce zinc levels — observe patient for signs and symptoms of zinc deficiency with long-term folate supplementation.
Supplemental (38-65 mg/day elemental) iron decreases zinc absorption (King 2003) — separate doses by 2 hours.
Zinc interacts with NSAIDs by forming complexes with these drugs — separate dose by 2 hours.
TETRACYCUNES AND QUINOLONES
Complex formation between zinc and tetracycline results in reduced absorption of both substances with potentially reduction in efficacy— separate dose by 2 hours.
THIAZIDE AND LOOP DIURETICS
These diuretics increase urinary zinc loss — monitor for signs and symptoms of zinc deficiency with long-term drug use. Increased zinc intake may be required with long-term therapy.
The efficacy of this drug is improved by supplementation with zinc sulfate (1 5 mg elemental zinc) for 6 weeks in children with ADHD. There is no change to side-effects reported.
Zinc acetate improved seroconversion of vibriocidal antibodies in children given a cholera vaccination in both faecal and serum titres.
Radiotherapy reduces plasma zinc levels. Supplementation may be required with intensive radiotherapy treatment.
Interferon-alpha and ribavirin treatment for hepatitis C patients is not affected by zinc supplementation.
Orlistat has no significant effect on zinc levels.
TRICYCLIC ANTIDEPRESSANTS AND SELECTIVE SEROTONIN REUPTAKE INHIBITORS
Zinc supplementation (25 mg elemental zinc daily) improves the efficacy of antidepressants such as tricyclic antidepressants and SSRIs after 2 weeks of intervention — beneficial interaction possible.
Contraindications and Precautions
Amiloride reduces zinc excretion and can lead to zinc accumulation (Reyes et al 1983). Therefore, supplementation should be used with caution.
Zinc is safe in pregnancy and may improve fetal heart rate in zinc deficient mothers (in conjunction with iron and folic acid).