DEFINITY® (Perflutren Lipid Microsphere) Injectable Suspension is an ultrasound contrast agent. The DEFINITY® vial contains components that upon activation yield perflutren lipid microspheres, a diagnostic drug that is intended to be used for contrast enhancement during the indicated echocardiographic procedures. The vial contains a clear, colorless, sterile, non-pyrogenic, hypertonic liquid, which upon activation with the aid of a VIALMIX®, provides a homogeneous, opaque, milky white injectable suspension of perflutren lipid microspheres. The suspension of activated DEFINITY® is administered by intravenous injection.

The perflutren lipid microspheres are composed of octafluoropropane encapsulated in an outer lipid shell consisting of (R) – hexadecanoic acid, 1-[(phosphonoxy)methyl]-1,2ethanediyl ester, monosodium salt (abbreviated DPPA); (R) - 4-hydroxy-N,N,N-trimethyl10-oxo-7-[(1-oxohexadecyl)oxy]-3,4,9-trioxa-4-phosphapentacosan-1-aminium, 4-oxide, inner salt (abbreviated DPPC); and (R)-?-[6-hydroxy-6-oxido-9-[(1-oxohexadecyl)oxy]5,7,11-trioxa-2-aza-6-phosphahexacos-1-yl]-?-methoxypoly(ox-1,2-ethanediyl), monosodium salt (abbreviated MPEG5000 DPPE).

Octafluoropropane is chemically characterized as 1,1,1,2,2,3,3,3-octafluoropropane. It has a molecular weight of 188, empirical formula of C3F8 and has the following structural formula:

Octafluoropropane Structural Formula Illustration

DPPA has a molecular weight of 670, empirical formula of C35H68O8PNa, and following structural formula:

DPPC has a molecular weight of 734, empirical formula of C40H80NO8P, and following structural formula:

MPEG5000 DPPE has an approximate molecular weight of 5750 represented by empirical formula C265H527NO123PNa, and the following structural formula:

Prior to VIALMIX® activation, the DEFINITY® vial contains 6.52 mg/mL octafluoropropane in the headspace. Each mL of the clear liquid contains 0.75 mg lipid blend (consisting of 0.045 mg DPPA, 0.401 mg DPPC, and 0.304 mg MPEG5000 DPPE), 103.5 mg propylene glycol, 126.2 mg glycerin, 2.34 mg sodium phosphate monobasic monohydrate, 2.16 mg sodium phosphate dibasic heptahydrate, and 4.87 mg sodium chloride in Water for Injection. The pH is 6.2-6.8.

After activating the contents of the vial in a VIALMIX®, each mL of the milky white suspension contains a maximum of 1.2 X 1010 perflutren lipid microspheres, and about 150 microL/mL (1.1 mg/mL) octafluoropropane. The microsphere particle size parameters are listed in Table 11.1 below:

Table 11.1: Microsphere Size Distribution

  Microsphere particle size parameters
Mean diameter range 1.1 ?m – 3.3 ?m
Percent less than 10 ?m 98%
Maximum diameter 20 ?m

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