ADVAIR DISKUS ADVAIR - GlaxoSmithKline

PHARMACEUTICAL INFORMATION
Drug Substance
PART II: SCIENTIFIC INFORMATION
Proper name:
Chemical name:
salmeterol xinafoate
4-hydroxy-α 1 -[[[6-(4-phenylbutoxy) hexyl]amino]-methyl]-1,3
benzenedimethanol, 1-hydroxy-2-naphthoate.
Molecular formula and molecular mass: C 25 H 37 NO 4 . C 11 H 8 O 3 603.8
Structural formula:
OH
H
HO
N
O
OH
HO
CO 2
H
Physicochemical properties:
Description: White to off-white crystalline powder with a melting point ~ 123 °C
Solubility:
In water ~ 0.07 mg/mL (pH = 8)
In saline ~ 0.08 mg/mL (0.9%w/v)
In methanol ~ 40 mg/mL
In ethanol ~ 7 mg/mL
In chloroform ~ 3 mg/mL
In isopropanol ~ 2 mg/mL
pKa and pH:
Salmeterol is amphoteric and is partially ionised in water over the whole pH range. The
ionised species have a low solubility, thus accurate determination of the two macrodissociation
constants by potentiometric titration has not been possible. The apparent
pKa for dissociation of the phenolic group (as determined by ultraviolet
spectrophotometry) is 9.3. The four microconstants lie between 8.9 and 9.7.
The pH of a saturated aqueous solution of salmeterol xinafoate (0.07 mg/mL) is about 8.
July 29, 2014
Page 34 of 67