Fluoride levels which can cause renal toxicity is

If a inhalational agent is highly metabolized and produces huge amount of fluoride it can cause nephrotoxicity. We need more than 50 micromol/litre of fluoride in blood to be nephrotoxic. Methoxyflurane is the most nephrotoxic among inhalational anesthetics- it causes polyuric renal failure due to a large amount of inorganic fluoride released, and it is no longer used in clinical practice. The renal toxicity of volatile anesthetics is due to their metabolic breakdown to free fluoride ions. The amount of fluoride ions produced: Methoxyflurane: 80uM Sevoflurane: 20-30 uM Enflurane: 20uM Isoflurane and desflurane: 5uMWhen compared to methoxyflurane, the lower incidence of nephrotoxicity among the newer inhaled anesthetics is due to lesser metabolic breakdown, lower solubility in the kidney which results in lesser amount of intrarenal fluoride which is liberated and also due to their faster clearance.