Comparative Excretion and Distribution of C¹⁴-Labeled Carbonate and Formate in Large Albino Rats

Absorption and Elimination of Formate Following Oral Administration of Calcium Formate in Female Human Subjects

“…Studies with perfused rat livers indicate that hepatic metabolism is sufficient to account for all of the formate oxidation observed in vivo (Damian and Raabe, 1996). Except at very high doses, the urinary excretion of formate is low, around 2 to 7% of the administered dose (Sperling et al, 1953;Friedmann et al, 1954;Malorny, 1969) and is limited by a renal transport system that recovers formate and a proton in exchange for chloride and sodium (Karniski and Aronson, 1985). On the other hand, the exhalation of 14 CO 2 accounts for up to 80% of administered doses of 14 C-formate with most of this being recovered in the first few hours, even after oral administration (Sperling et al, 1953;Friedmann et al, 1954;Palese and Tephly, 1975).…”

“…Except at very high doses, the urinary excretion of formate is low, around 2 to 7% of the administered dose (Sperling et al, 1953;Friedmann et al, 1954;Malorny, 1969) and is limited by a renal transport system that recovers formate and a proton in exchange for chloride and sodium (Karniski and Aronson, 1985). On the other hand, the exhalation of 14 CO 2 accounts for up to 80% of administered doses of 14 C-formate with most of this being recovered in the first few hours, even after oral administration (Sperling et al, 1953;Friedmann et al, 1954;Palese and Tephly, 1975). However, because of endogenous metabolic incorporation of formate into tissue components, the carcass retains up to 10% of the dose of 14 C-formate even after 8 days (Sperling et al, 1953).…”

“…Formate ion distributes readily throughout total body water (Liesivouri and Savolainen, 1991) and under normal conditions appears in plasma or serum at concentrations of 0.02 to 0.25 mM (Annison, 1954;Friedmann et al, 1954;Osterloh et al, 1986Osterloh et al, , 1996Sivilotti et al, 2001); the concentration of formate in the erythrocytes of several species including humans is about twice that of plasma (Annison, 1954). Upon intraperitoneal or oral administration of 14 C-formate to animals, exhalation of 14 CO 2 commences almost immediately at rates that are dose-proportional and with saturation clearly observable at very high doses (Sperling et al, 1953;Palese and Tephly, 1975). The very rapid absorption of formate from both the peritoneal cavity and the gastrointestinal tract is consistent with its ease of distribution throughout total body water.…”

“…On the other hand, the exhalation of 14 CO 2 accounts for up to 80% of administered doses of 14 C-formate with most of this being recovered in the first few hours, even after oral administration (Sperling et al, 1953;Friedmann et al, 1954;Palese and Tephly, 1975). However, because of endogenous metabolic incorporation of formate into tissue components, the carcass retains up to 10% of the dose of 14 C-formate even after 8 days (Sperling et al, 1953).…”

Formate pharmacokinetics during formate administration in folate-deficient young swine

“…Excess formate production may then lead to formate accumulation and toxicity such as optic nerve damage, increased anion gap, and metabolic acidosis [8,9]. Urinary excretion of formic acid is low (about 2%-7%) [10][11][12].…”