The acute nephrotoxicity of systemically administered formaldehyde in rats

The purpose of this study was to assess the acute nephrotoxicity of formaldehyde, as it is believed to be the toxic component of formocresol.

A sample of 24 Sprague-Dawley rats was used in the study and divided into 3 groups of 8 rats each. The following procedures were performed: group A) formaldehyde equivalent dose to 20 pulpotomies, injected into the main vein of each rat's tail; group B) formaldehyde equivalent dose to 100 pulpotomies injected; group C) control group with a saline solution injected. Blood analyses were performed after 24 and 48 hours to assess urea and creatinine levels. Urine samples were taken after 24 hours to analyse for LDH protein levels. Rats were sacrificed after 48 hours and histology samples of renal tissue were studied for any pathological defects.

Evaluation of histological samples of kidney tissue did not show any inflammation or other tissue lesions. No significant differences were found, using an ANOVA test procedure, among the variables of LDH protein or creatinine levels after 24 and 48 hours. Significant differences were found between the levels of urea and creatinine after 48 hours between the control group and the other test groups.

The use of formaldehyde at the usual clinical doses or with an amount equivalent to 100 pulpotomies did not produce renal tissue damage and the blood and urine factors analysed did not show significant changes after 48 hours in the experimental model used.