Zinc pharmacokinetic parameters in the determination of body zinc status in children

Zinc supplementation as an adjunct therapy for COVID-19: Challenges and opportunities

An outbreak of a novel coronavirus (COVID‐19 or 2019‐CoV) infection has posed significant threats to international health and the economy. Patients with COVID‐19 are at risk of cytokine storm, acute respiratory distress syndrome (ARDS), reduced blood oxygenation, mechanical ventilation, and a high death rate. Although recent studies have shown remdesivir and dexamethasone as treatment options, there is an urgent need to find a treatment to inhibit virus replication and to control the progression of the disease. Essential biometal zinc has generated a lot of excitement as one of the promising candidates to reduce the severity of COVID‐19 infection. Several published observations outlined in the review are the reasons why there is a global enthusiasm that zinc therapy could be a possible therapeutic option. However, the biggest challenge in realising the therapeutic value of zinc is lack of optimal treatment modalities such as dose, duration of zinc supplementation and the mode of delivery. In this review, we discuss the regulatory mechanism that hinges upon the bioavailability of zinc. Finally, we propose that intravenous zinc could circumvent the confounding factors affecting the bioavailability of zinc and allow zinc to achieve its therapeutic potential. If successful, due to advantages such as lack of toxicity, low cost and ease of availability, intravenous zinc could be rapidly implemented clinically.

Does infusion time affect the retention of parenteral trace elements?

When readymade parenteral nutrition in multi-chamber bags is supplied without vitamins and minerals, these have to be added or given separately. Separate rapid infusion has logistical advantages but has been claimed to saturate tissue mechanisms, potentially increasing urine micronutrient losses. The present study compared urinary losses after fast (1 h) v. slow (10 h) trace elements infusion. The study enrolled thirty-nine consecutive patients who were starting parenteral nutrition postoperatively. One day’s dose of a complete intravenous micronutrient product was infused over 1 h and over 10 h, in random order, with a washout day after each infusion day. Urinary Zn, Mn, Se, Cr, Cu and Fe losses were measured by 24-h urine collection, recorded for each infusion day and subsequent washout day. For Zn, a dose of 100 μmol was given, and total urinary loss over the next 2 d was mean 40·6 (sd 23·8) μmol after the fast (1 h) infusion v. 33·4 (sd 25·4) μmol after the slow (10 h) infusion, that is, 7 % more of the 1-d dose was lost after fast infusion (P = 0·01). For Mn, after a dose of 1000 nmol, losses were 9·8 (sd 23·9) nmol after the fast infusion v. 22·1 (sd 47·2) nmol after the slow infusion, that is, 1 % more of the 1-d dose was lost after slow infusion (P = 0·04). There were no other significant differences: after 1 μmol Se, the losses were 1·5 (sd 0·6) μmol fast v. 1·3 (sd 0·5) μmol slow; after 200 nmol Cr, 257 (sd 92) μmol fast v. 246 (sd 107) nmol slow; after 8 μmol Cu, 1·6 (sd 1·4) μmol fast v. 1·5 (sd 1·3) μmol slow; and after 20 μmol Fe, 0·6 (sd 1·1) μmol fast v. 0·8 (sd 1·6) μmol slow (P > 0·05 for all). Overall, trace element retention appears to be minimally affected by infusion time.

Drug-development concepts as guides for optimizing clinical trials of supplemental zinc for populations at risk of deficiency or diarrhea

Studies on the efficacy of zinc supplementation for treatment or prevention of diarrhea have shown an inconsistent effect in populations at risk for zinc deficiency. Unlike drugs, which have no preexisting presence in the body, endogenous zinc must be assessed pharmacokinetically by isotope tracer studies. Although such methods have produced much data, very few studies have estimated the dose and the timing of dosing of zinc supplementation. This review examines drug kinetics used to establish the best dose, the timing of such doses, and the mechanism of action through pharmacodynamic markers and applies them, where possible, to zinc supplements. The findings reveal that little is known, especially in children at highest risk of zinc deficiency. Key data missing to inform proper dosing, whether for treatment of disease or for preventive nutrient supplementation, are noted. Addressing these uncertainties could improve study design, leading to future studies of zinc supplements that might be of greater benefit.

The potential for zinc stable isotope techniques and modelling to determine optimal zinc supplementation

It is well recognised that zinc deficiency is a major global public health issue, particularly in young children in low-income countries with diarrhoea and environmental enteropathy. Zinc supplementation is regarded as a powerful tool to correct zinc deficiency as well as to treat a variety of physiologic and pathologic conditions. However, the dose and frequency of its use as well as the choice of zinc salt are not clearly defined regardless of whether it is used to treat a disease or correct a nutritional deficiency. We discuss the application of zinc stable isotope tracer techniques to assess zinc physiology, metabolism and homeostasis and how these can address knowledge gaps in zinc supplementation pharmacokinetics. This may help to resolve optimal dose, frequency, length of administration, timing of delivery to food intake and choice of zinc compound. It appears that long-term preventive supplementation can be administered much less frequently than daily but more research needs to be undertaken to better understand how best to intervene with zinc in children at risk of zinc deficiency. Stable isotope techniques, linked with saturation response and compartmental modelling, also have the potential to assist in the continued search for simple markers of zinc status in health, malnutrition and disease.