Flunisolide hemihydrate
is administered by inhalation from metered
aerosol and used in the management of
asthma.
Synthetic fluorinated corticosteroid related to Prednisolone (P703740). Antiasthmatic.
ChEBI: Flunisolide is a fluorinated steroid, a cyclic ketal, a 20-oxo steroid, a 21-hydroxy steroid, an 11beta-hydroxy steroid, a 3-oxo-Delta(1),Delta(4)-steroid and a primary alpha-hydroxy ketone. It has a role as an immunosuppressive agent, an anti-inflammatory drug and an anti-asthmatic drug.
(a) Preparation of 6α-fluoro-16α-hydroxyprednisolone: 1.9 liters of whole
mash containing 400 mg of 6α-fluoroprednisolone (6α-fluoro-11β,17α,21-
trihydroxy-1,4-pregnadiene-3,20-dione) acted upon by Streptomyces
roseochromogenus AE-751 (or Waksman No. 3689) is filtered and the filtrate
extracted three times with 2 liter portions of ethyl acetate. The mycelium is
extracted with 500 ml of ethyl acetate and the mixture filtered. The combined
ethyl acetate extracts are washed with 200 ml of water and concentrated to a
residue. The residue is subjected to partition chromatograph using a 200 g
column of diatomaceous earth moistened with the lower phase of an
equilibrated solvent system composed of 1 volume of water, 5 volumes of
dioxane, and 3 volumes of cyclohexane. The upper phase is used to develop the column and the activity of the eluent is followed by measuring the
ultraviolet absorbance at 240 mμ. The cuts containing most of the activity are
concentrated to a syrupy residue and triturated with acetone. Crystals (25
mg) form and recrystallization gives a product with a MP of 226°C to 230°C.
(b) Preparation of 16α,17α-isopropylidenedioxy-6α-fluoro-1,4-pregnadiene-
11β,21-diol-3,20-dione: 15 mg of crystalline 6α-fluoro-11β,16α,17α,21-
tetrahydroxy-1,4-pregnadiene-3,20-dione [6α-fluoro-16α-hydroxyprednisolone
described in US Patent 2,838,546 and prepared as described in (a) above] is
dissolved in 2 ml of acetone and 0.02 ml of 70% perchloric acid is added. The
solution is allowed to stand 1 hour. Then 0.5 ml of saturated sodium
bicarbonate solution is added and the solution concentrated under reduced
pressure to about 1 ml. The solution is allowed to stand overnight and the
crystals which form are filtered, washed with ether and recrystallized from
acetone-hexane. The crystals are the 16α,17α-isopropylidene derivative of 6α-
fluoro-16α-hydroxyprednisolone.
Aerobid (Roche); Aerospan Hfa (Forest); Nasalide (IVAX); Nasarel (IVAX).
The portion of a flunisolide (AeroBid,Nasarel) dose that is swallowed is rapidly converted to the6β-hydroxy metabolite after first-pass metabolism in theliver. The 6β-hydroxy metabolite is approximately as activeas hydrocortisone itself, but the small amount produced usuallyhas limited systemic effects. Water-soluble conjugatesare inactive.
Flunisolide is an acetone ketal (acetonide) with a 6α-fluoro group and a free C-21 hydroxyl
group. The acetonide decreases mineralocorticoid activity, and the 6α-fluoro group increases
glucocorticoid activity. It is not a prodrug, because it has the free hydroxyl group at C-21.
Flunisolide has approximately 20% of the receptor affinity as budesonide, and approximately 40%
of the inhaled dose is systemically bioavailable.
When administered intranasally or by inhalation, flunisolide is rapidly absorbed
from nasal or lung tissue(94). This corticosteroid is efficiently metabolized by the liver to inactive
metabolites with no apparent effects on adrenal function with long-term therapy. Flunisolide that is swallowed undergoes extensive first-pass metabolism in the liver, and that which is absorbed directly from the
nasopharyngeal mucosa or lung bypasses this initial metabolism. It is not known if the drug undergoes
metabolism in the GI tract.
Flunisolide is rapidly hydroxylated by CYP3A4 at the 6β position, followed by
elimination of the 6α-fluoro group to its more polar 6β-hydroxy metabolite, which attains plasma concentrations
that usually are greater than those for flunisolide.
