Fludrocortisone Other names: Fluorohydrocortisone

Qualitatively, the physiological action of fludrocortisone acetate is similar to hydrocortisone. In very small doses, fludrocortisone maintains life in adrenalectomised animals, enhances the deposition of liver glycogen and produces thymic involution, eosinopenia, retention of sodium and increased urinary excretion of potassium.

Absorption

Fludrocortisone is rapidly and completely absorbed after oral administration.

Biotransformation

Man, dog, rat, monkey and guinea-pig were studied after i.v. and intraduodenal administration. Depending on species, 50% or more of the steroid remained unchanged 30 minutes after administration. Fludrocortisone is hydrolysed to produce the non-esterified alcohol; after administration of the acetate, only the non-esterified alcohol is detectable in blood. The blood level reaches a peak between 4 and 8 hours. The highest blood level after i.v. administration to human volunteers was 1.7 hours.

Distribution

Fludrocortisone is widely distributed throughout the body. It is 70 to 80% bound to serum proteins, mainly to the globulin fractions. The concentrations ratio of the drug in CSF to that in plasma was 1:6 in human volunteers.

Elimination

Elimination half-life after i.v. administration was 30 minutes in dogs and in human volunteers. Following administration of the acetate to dogs, the blood concentration shows a triphasic decline and each phase may represent the elimination of a metabolite.

In rats, most of a dose is excreted in the bile, and in dogs and guinea-pigs most of the dose is excreted in the urine. In human volunteers, excretion through urine was about 80%, and it was concluded that about 20% were excreted by a different route. It is likely that, as for the metabolism of other steroids, excretion into the bile is balanced by re-absorption in the intestine and some part is excreted with the faeces.

No studies have been conducted.