Preparation, chemical analysis and sub-acute toxicity evaluation of linga pathangam (a mercury based Siddha herbo-metallic drug) in rats

Objective: Lingapathangam (LP) is a mercury based herbo-mineral drug used in Siddha Medicine for the management of chronic autoimmune arthritis. The toxicity profile of the drug has not been reported. This study was conducted to prepare LP as per traditional literature, evaluate chemical composition and to study the sub-acute toxicity of the LP in rats. Methods: LP was prepared as per the traditional literature Anupoga Vaithiya Navaneetham Part-IV in our lab. The physico-chemical analysis was done to find out the presence of organic and inorganic compounds. Acute toxicity study was conducted in rats by administering single oral dose of three strengths. Abnormal behavior and death were observed for 14 days. Sub-acute toxicity study was done in rats by administering three different doses (2, 10 and 20 mg/kg) orally for 21 days. Body weight, food intake, water intake were monitored every day. At the end of the study, blood was collected from rats to estimate renal function parameters, liver function parameters, hematology parameters and lipid profile. Organs such as brain, lung, stomach and liver were collected for histopathology assessment. Results: Quantitative analysis has revealed that 100gm of LP contains 70.43% mercury, 14.10% chloride, 1.80% silica and 0.98% sulphate and the absence of organic matter. Acute toxicity study suggests that LP fall under the category 2 (LD50 is > 5 - 50 mg/kg), which is considered as highly toxic category. Sub-acute toxicity revealed that LP is safe up to 10mg/kg. There is no renal impairment even at high dose (20mg/kg). LP at high dose produced toxicity in blood parameters, liver functions and lipid profile, and showed mild histological changes. Conclusion: Linga pathangam is safe up to 10mg/kg in rats, which corresponds to human dose of 112mg/70kg in man. The currently practiced clinical dose (50mg/day) given with palm jiggery only up to 7 days is considered as the safe and non-toxic dose.