Monograph: |
Hypromellose
NOTE. HPRM is a code approved by the BP for use on single
unit doses of eye drops containing hypromellose where the in-
dividual container may be too small to bear all the appropriate
labelling information.
A mixed ether of cellulose containing a variable proportion of
methoxy and 2-hydroxypropoxy groups. Several grades are
available. In the UK these are distinguished by appending a
number indicative of the apparent viscosity in millipascal sec-
onds of a 2% w/w solution measured at 20Β° (e.g. hypromel-
lose 4500). In the USA they are distinguished by appending a
number in which the first 2 digits represent the approximate
percentage content of methoxy groups, and the third and
fourth digits the approximate percentage content of hydroxy-
propoxy groups. Standards for hypromellose 1828, hy-
promellose 2208, hypromellose 2906, and hypromellose
2910 are given in the USP.
A white, yellowish-white, or grayish-white, practically
odourless fibrous powder or granules; hygroscopic after dry-
ing. Dissolves in cold water, forming a colloidal solution:
practically insoluble in hot water, dehydrated alcohol, ace-
tone, chloroform, ether, and toluene. A 1% w/w solution in
water has a pH of 5.5 to 8.0.
Uses and Administration
Hypromellose has properties similar to those of methylcellu-
lose. It is used in pharmaceutical manufacturing for
film-coating tablets, as a tablet binder, as an extended-release
matrix, and as an emulsifier, suspending agent, and stabilizer
in topical gels and ointments. Hypromellose may also be used
as an emulsifier and stabiliser in the food industry.
Hypromellose phthalate is used to provide enteric coating for
tablets and granules, for the preparation of sustained-release
granules, and as a coating to mask the unpleasant taste of
some tablets.
Hypromellose is widely used clinically in ophthalmic solu-
tions: it is preferred to methylcellulose since mucilages of hy-
promellose have greater clarity and usually contain fewer
undispersed fibres. Hypromellose is used to prolong the ac-
tion of medicated eye drops and. either alone or in combina-
tion with other viscosity-increasing agents, in artificial tears
preparations for the management of dry eye, solu-
tions containing 0.3 to 1% of hypromellose are commonly
used. Solutions for contact lens care and for lubricat-
ing artificial eyes contain similar concentrations. Hypromel-
lose is also administered intra-ocularly, usually as a 2%
solution, as an adjunct in ophthalmic surgery and
concentrations of up to 2.5% may be used topically to protect
the cornea during gonioscopy procedures.
Hypromellose has been included in artificial saliva prepara-
tions used in the management of dry mouth. but oth-
er drugs are usually preferred.
Ophthalmic surgery. Intra-ocular hypromellose may be
used as a visco-elastic agent to protect the eye during surgery.
In cataract extraction it is employed to maintain the anterior
chamber and to coat the intra-ocular lens to facilitate its im-
plantation. Although intra-ocular hypromellose is generally
considered to be well tolerated, some workers reported an
increased incidence of pupil abnormalities (non-reactive
semi-dilated pupils) following such use: others did not con-
firm this.
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