Monograph: |
Propylene Glycol
A clear, colourless, odourless or almost odourless, viscous.
hygroscopic liquid with a slight characteristic taste. Miscibic
with water, with acetone, with alcohol, and with chloroform;
soluble in ether; immiscible with fixed oils but will dissolve
some essential oils. Store in airtight containers.
Adverse Effects and Precautions
Propylene glycol may cause some local irritation of the skin
and mucous membranes. Hypersensitivity reactions have
been reported. Hyperosmolality, lactic acidosis. and central
nervous system depression have occurred, particularly in pa-
tients with renal impairment. Hyperosmolality has also been
reported in bum patients following the topical application of
preparations in which the basis is propylene glycol.
Effects on the blood. Studies have indicated that propylene
glycol may have a haemolytic effect and haemolysis in one
patient has been attributed to the administration of red blood
cells and 50% propylene glycol through the same intravenous
line.
Effects on the ears. Chloramphenicol sodium succinate
5% in Ringer's solution and propylene glycol 10% both
caused irreversible deafness when instilled into the middle-
ear cavity in guinea-pigs. It was recommended that propyl-
ene glycol should not be used as a solvent for chlorampheni-
col ear drops.
Effects on the nervous system. Central nervous system
toxicity in children has been associated with propylene glycol
used as a solvent in some oral vitamin preparations. Stupor
has been reported and a 15-month-old boy had episodes of
unresponsiveness, tachypnea, tachycardia, and diaphoresis
until the vitamin preparation was discontinued. There have
also been isolated reports of seizures associated with inges-
lion or use in preparations for parenteral nutrition.
Fluid and electrolyte homoeostasis. Intravenous infu-
sions of preparations containing a high proportion of propyl-
ene glycol as a solvent have been associated with increased
senim osmolality, especially in small infants (for example
those under 2kg body-weight) and in patients with diminished
renal function. Hyperosmolality following the transdermal
absorption of propylene glycol from a topically applied silver
sulphadiazine preparation has been reported inpatients with
extensive bums and toxic epidermal necrolysis. The moni-
tonng of osmolality in susceptible patients receiving high
doses of propylene glycol has therefore been recommend-
ed. Patients with renal impairment exposed to propylene
glycol have also developed lactic acidosis possibly due to the
metabolism of propylene glycol to lactic acid in the liver and
its subsequent accumulation.
Hypersensitivity. Skin reactions due to propylene glycol
are generally rare. Irritation of the skin may occur, especial-
ly under occlusive conditions and hypersensitivity-type re-
actions have been reported.
Interactions
Propylene glycol has been reported to decrease the effect of
heparin.
Pharmacokinetics
Propylene glycol is rapidly absorbed from the gastro-intesti-
nal tract. There is evidence of topical absorption when ap-
plied to damaged skin.
It is extensively metabolised in the liver primarily by oxida-
tion to lactic and pyruvic acid and is also excreted in the urine
unchanged.
Uses and Administration
Propylene glycol is widely used in pharmaceutical manufac-
turing as a solvent and vehicle especially for drugs unstable
or insoluble in water. It may also be employed as a stabilising
agent in vitamin preparations, a plasticiser, and as a preserv-
ative. Propylene glycol is also used extensively in foods and
cosmetics.
Propylene glycol has humectant properties and is used simi-
larly to glycerol in topical moisturising preparations.
Propylene glycol is used in veterinary medicine as a glucose
precursor.
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