Drug and heavy metal toxicity with special reference to calcium channel blocker overdose, inorganic mercury poisoning and blood lead level

Abstract

Toxicity due to drug overdose and heavy metals are issues of public concern. Of the heavy metals, mercury and lead are significant environmental hazards worldwide. Calcium channel blockers are now the most commonly used group of drugs for treating hypertension. They are therefore found in large quantities in many homes, creating a hazard because of the possibility of a large overdose.

Inorganic Mercury poisoning due to cosmetic products could induce pathological changes in kidney. Patients may present with proteinuria, minimal disease change or even membranous nephropathy upon admission. The efficacy of corticosteroid in these patients is in debate. The Poison Information and Clinical Management System (PICMS) was used to identify patients with inorganic mercury poisoning with nephrotic symptoms due to cosmetic products in this study. Efficacy of concomitant treatment of corticosteroid in patients with inorganic mercury poisoning due to cosmetic cream in Hong Kong was compared among patients received different treatment regimen. There is significant difference in the duration of achieving proteinuria remission since admission. Baseline urine protein levels were not correlated with the baseline blood or urine mercury levels.

Lead is a heavy metal without any biological role(s) in human. This toxic metal has been associated with reduced intelligence in children even at low level. There is no safe blood lead level identified in the previous studies and the level of toxicity is significantly correlated with increase in blood lead level. The current blood lead reference level is 5μg/dL which is based on 97.5 percentile in the United States (US) National Health Nutrition and Examination Survey (NHANES). The NHANES database was used to study the latest trend in the blood lead level in the US population. The blood lead level in the United States has been continual decreasing trend. The mean blood lead level has been decreased from 1.65 (1.62-1.68) μg/dL in 1999-2000 to 0.84 (0.82-0.86) μg/dL in 2013-2014 significantly. The estimated proportion of children aged 1-5 years with elevated blood lead level was 0.5 [0.3-1.0]% in 2013-2014. The estimated new blood lead reference level was 3.48μg/dL.

Calcium channel blocker overdose is a potentially fatal poison in Hong Kong. Insulin and glucagon are common antidotes for treating calcium channel blocker overdose. The PICMS was also used to compare the mortality rate between insulin and glucagon in patients with calcium channel blocker overdose. There was no significant difference in mortality rate between insulin and glucagon. Compared to survived patients, there was significant difference in baseline systolic blood pressure, serum albumin level, serum alanine aminotransferase activity and PR interval in electrocardiogram in dead patients. Baseline serum albumin and systolic blood pressure were associated with mortality in patients with calcium channel blocker overdose.