Download Dextran - HPMC Eye Drops As Artificial Tears

Journal of Sci entifi c & Industri al Research
Vol. 59 , December 2000, pp 1027-103 1
Dextran - HPMC Eye Drops As Artificial Tears
Milind Redkar, B Srividya, P Ushasree and P D Amin*
University Department of Che mi cal Technology (Autonomous), Matun ga,
Mumbai 400019 , lndi a.
Recei ved: 24 Janu ary 2000; accepted 2 1 August 2000
In the present study, a formula ti on containing a combinati on of dextran and hydroxypropyl methylcellul ose (HPMC ) was
developed where HPM C, a vi scosity-imparting agent , forms a thin film over precornea l tear film while dex tran provides mechani cal strength to thi s film. The formul ation was developed by studyin g various polymers. A buffer system was selected to
ac hieve an alkaline pH . Various preserv atives were evalu ated and J suit able antim icrobial preservati ve hav ing suitab le concentration was selected. Eye drops were evaluated for pH , viscosity, clarity, light stabilit y, dex tran, and HPMC content , and steril it y.
Ocular irrit ation studies and Schirmer 's test we re carried out on rabbits. The final formulation was subj ected to accelerated
thermal studi es . The developed formulation WJS non-irrit ant and showed optimum vi scosity. It had beller film forming properties
and improved welling characteri sti cs than the marketed formulation MOISOL®. The developed formulation has potenti al as
artifici al tears in the treatment of dry eye syndrome.
Introduction
Dry eye syndrome is a condition which results
from a deficiency of either the aq ueou s or mucin
component of the precoineal tear fi 1m. Patients complain of severe ocular pain due to a sensation of dryness in the eyes . The terms dry eye and kerato conjunctivitis sicca (KCS) are most commonly used to
indicate problems of the ocular surface connected
with the reduction or instability of the precorneal
tear filml. The dry eye syndrome is most commonly
found in individuals who spend most of their tim e
in front of Video Display Terminal s (VDTs) , e .g .,
PCs and computer games. The prolonged use of
VDTs is associated with a decreased frequency of
blinking and an increased rate of tear evaporation.
Thi s leads to ocular fatigue which is one of th e major symptoms of dry eye. The underlyin g causes of
dry eye can be as follows:(i) aqueous tear deficiency,
(ii) mucin abnormalities, (iii) impaired lid function .
Due to persi stent disruption of tear fi Im, the symptoms of KCS develop . Tn KCS , mild de g ree of
conjuctival infection is associated with considerable
irritation, photophobia, foreign body sensation , and
burning2.
* For co rrespondence
Artificial tear formulations fulfill the physicochemical role of a normal tear. Artificial tears effectively lower the surface tension of the tear fi lm ,
aid the formation of hydrophilic layer that is compatible with absorbed mucin , and enhance tear vo lume when necessary. Thus the mainstay of treatme nt of dry eye conditions remains the supplementation of tear production by artificial preparati o ns.
Almost all the artificial tears available in the
market contain hydrophilic polymer system . The
objective of the present work was to develop artificial tears with hydroxypropyl methylcellulose
(HPMC) and dextran, which are hydrophilic polymers. The rationale for their use is that HPMC is a
viscosity-imparting agent and it forms a thin f ilm
over precorneal tear film , while dextran pro vides
the mechanical strength to thi s film.
Materia
Is and Methods
For the selection of raw mate rial s, based on the
req uirements of ideal artificial tears , diffe rent pH
and tonicity adjusting agents were studied , with spec ia l emphasis o n hydrophili c polyme ri c syste m ,
J SCI IND RES VOL. 59 DECEMBER 2000
1028
Table I Formulation
C larit y
pH
Eva lu ati on of formula ti ons
Sp.
V i scos it y
gr~vity
(c P)
A
C lear
H. 16
I. OO<)l)
26.75
B
Clear
X.I I
1.0 I 06
6S. 02
C
Clea r
H. 16
1.00%
1.10
D
Clear
X. 15
I .009X
25.4<)
E
Clear
S. 17
1.0098
7 1.46
MOISOL®
Clear
IUO
1.0079
42.30
whi ch decides the tear film characteristics, as well
as the viscosi ty.
(AJ Forlllulation Development
Based on tear studies the requirements of an idea l
tea r substitutes are : (a) Shou ld be isoto ni c, (b)
Should have pH 01'7.4 ± 0. 1 which is equivalent to
tear fluid pH , (c) Should contain preservatives to
prevent mi crobi al growth , (d) Shou ld have viscosity in between 25 to 50 cP, and (e) Sho ul d be steril ized by suitabl e method.
Initially, isoto ni c buffer veh ic le was se lected.
Though the eye is tolerant to toni city variation, given
a choi ce, isotonicity is always desirab le. 1n th e
present study, sodium chl oride (0.45 % w/v) was usee!
as a tonicity adjust ing agent. Freezing poi nt method
and mo lec ul ar concentration meth od we re used to
ca lculate the amount of NaCI requi red . The buffered veh icle for the eye drops was prepared in order
to prepare alkaline so luti on havin g pH about 7.4.
However, pH of th e formulation was se lec ted to be
8. 1, for achieving the stabi lity or the polymeric system. Borax and boric acid buffer were used as th e
veh icle for th e form ulati on. It was prepared by disso lvi ng 0.19 g of boric ac id , 0.19 g of bo ra x, and
0.35 g of potassium chloride in 100 1111 o r puri fied
water.
The nex t step was to select a suitab le antimi crobial preservative. Benzalkonium chlorid e (BKC),
pheny lmercuri c nitrate, and chl orbutanol were con sidered. PMN was rejected as the use of orga nic
mercuri als is restri cted to neutral to alkalin e so lu ti o ns and as PMN has been repor ted to cause
mercurial entes. Chlorbutanol was avo ided because
of its reported slow action , and formul at ion and
packaging difficulti es. BKC (0.0 I percent w /v) was
selected as the prese rvati ve for the system .
Fin all y the selec tion of the polymeri c system was
made. Viscosity of artificia l tears may be achieved
between 2.5 to 50 cP by viscosity imparting agen ts
such as polyvi ny l alcohol (PVA ) and ce llul osic polyme rs s uch
as
me th ylce llu lo se (MC),
hydrox ypro pylcellul ose (HPC), and hydroxypropy l
met hylcellul ose (HPMC) . To stud y different viscosity impartin g age nts, roll ow in g fo rmulati ons with
varyin g polymers and thei r combin atio ns were prepared (Tab le I)
Formula A = HPMC K4M alone (0.7 per cent
w/v) in borate buffe r pH 8.0.
Formula B = HPC MFF (0.7 pe r cent w/v)
alone in bo rate buffer pH 8.0.
Formula C = Dex tran 70 (0.1 er cent w/v)
alon e in borate bu ffe r pH 8.0.
Formul a D = HPM C K4M (0.7 percent w/v )
and dex tran 70 (0.1 pC I' cent "v/v) in borate
buffer pH 8.0.
Formu la E = HPC MFF (0.7 percent w/v ) and
REDKAR ('/ 01.: DEXTRAN -
I-IPMC EYE DROPS AS ARTIFICIAL TEA RS
0.5
dextran 70 (0.1 per cent w/v) in borate buffer
pH 8.0.
1029
~---------------:;c------,
0.4
(B) Evaluation ol Opht/w/Illic SoluTions
The prepared formulations were eva luated for the
following :
b
.;;
Clarity
"§'"
'oa
The ophthalmi c formu lation fill ed into vial s was
observed for the presence of mctal/glass particles,
precipitates, etc., against different background in a
well-lit cabinet.
OJ
·c
t.)
0.2
y ~ O.0002x - 0.0033
0.1
R2 ~ 0.998
O ~-~---r--.---.---.-~
500
1000
1500
2000
2500
3(
-0.1 L _ _ _ _ _ _ _ _ _ _ _ _ _ _-.--J
pH
Adequate volume of the formulation was taken
in a 50 ml beaker and the pH was recorded on a
standardized Systroni c pH mcter.
Specific Gravity
concentration (mcglml)
Figure I -
Standard cur ve of de xtran 70
Content of Dextran 70 and HPMC
Specific gra vity of the formulation was measured
by using specific gravity bottle of 10 ml capacity
using purified water as standard .
We ight or 10111 101' rorlllulatioll
Sp. gra vity of formul ati on
=
Weight of 10 1111 of purified water
Viscosity
Viscosity of the formulation was measured usin g
Osw ald 's Vi sco meter o. 3. The viscos ity studies
were ca rri ed at constant temperature of 20°C and
purifi ed water was used as a sta ndard. Form ula used
to determine the viscos ity was:
=
where 11 I = viscosity of the forll1ula l iU Il. 11 0_ = viscosity of purified water at 20" C = 1.008 6, PI =Sp.
gra vity offormulati on, p ~ = Sp. :;raYlly of purified
water at 20 0 C, I I = limc lakcll h) i"(lrIl1Ulali on in
scconds , Jnd 12 = time l~l kcn hy purified waler ill
seconds.
Dextran 70 is an opticall y ac tive compound . Its
optical activity was used to analyze its content. A
standard curve of dextran 70 was plotted using a
Carl Zeiss polarimeter ~md the percent content of
dextran in the formulation was found out by ex trapolati on (Figure I).
Since HPMC and dextran are carbohydrates the
anth rone method was used to find out total content
of ca rbohydrates in the formulation. The principl e
behind anthrone reaction is th at all carbohyd rates ,
onlreatment with concentrated H 2S0 4 , undergo acid
hyd roly sis to fo rm glucose, which on heat in g undergoes dehyd rati on and rin g formation to produ ce
a i"urfu ral deri vative. Thi s derivative produ ces a
co lour in the presence of anthrone, which can be
detected by UV spectrophotometry. A standard curve
was first establi shed usin g the same ratio of HPMC
an e! dextran prese nt in th e fo rmulati on. The tOlal
carbohydrate co nten t in thc formu lat ion was determin ed by ex trapolati on from th e sta ndard cur ve
(Table 2).
From th e total ca rbohydrate content the aillount
of dex tran obta ined from polarimetry experiment
was subtracted to give th e content of HPM C in the
fo rmulati on.
J SCI IND RES VOL. 59 DECEMBE R 2000
1030
Table 2 -
Standard clirve or HPMC alld dextran
HPMC
Dex tran 70
Total carbohydra te
( ~ g/m l )
~g/m l )
( ~ g/ m l )
42
6
48
84
12
126
Abso rba nce
0.326
Regress ion Ana lys is
96
0 .594
r = 0.9954
18
144
0.864
Slope = .005708
168
24
192
1.070
2 10
30
240
1.478
(C) Stability Studies
Stability of the fo rmul ation was studied under the
fo ll ow in g:
Acceler ated Thermal Studies
The selected fo rmul ati on of dex tran-HPMC
eye drops was subj ected to stability studi es at vari ous temperatures, i.e., room temperature, 37°C and
5°C. The eye drops we re evalu ated at every 15 d fo r
a peri od of six months fo r cl arity, pH, viscosity, specific gravity, per cent content of dex tran and HPMC.
Light Sta bility Studies
The effect of li ght on the ph ys ica l and chem ical
stabili ty was examined by ex pos ing the fina l formul ati on in clear glass vi als to direc t sunli ght and
checkin g fo r cl ari ty and di sco lorat ion.
Autoclaving Studies
To check fo r the stability of the fo rmul ati on during terminal sterilization, i.e., autoc lav in g, it was
ex posed to autoc lavi ng condi tions at 12 1°C and 15
psi fo r 15,20 and 30 min , respecti vely. The hi gher
time po in ts were used in an attempt to force degradation.
Sterility Tes tin g
The devc loped fo rmul ation was tested for the
presence or absence of fungi and aerobic and anaerobic bacteria by membrane filt ration techniquc in the
presence of posit ive and negative controls.
Y -in tercept
= 0.0404
(D) Animal Studies
To determine the efficacy of the form ul ati on, studies we re carri ed out on rabbits usin g the marketed
preparation MOISOL® for comparative purpose.
(i) Schirmer 's Tes t "
The test was performed by usi ng Whatman fil te r
paper No.4. I strips of 35 mm by 5 mm dimensio n.
The first 5 mm at one end of the paper stri p was
bent to work as a hook for eyeli ds (Thi s porti on was
not included when the length of the mo istened stri p
was measured). The paper notch was in serted in to
the conjunctival fo rni x fo lded, whe re it was left in
pos iti on. The amoun t of wetting of stri p was measured after 5 min and the strip was re moved. Since
the instill ati on of pape r may produce some reflex
tears the eye was anaes theti zed by in stillin g a local
anaetheti c so lu tion (xy locaine 0.5 per cent) 10 min
pri or to the in se rti on of stri p.
(ii) Ocular Irrita tion Studies
Assessment of ocu lar irritation potenti al of ophthalmic so lu tion is an extreme ly important step in
the development of ophth almic product. Six rabb its
we ighin g 2-3 kg each were used for the study. Each
ti me, 2 drops of the fo rmu lation were ins til led into
the cul -de-sac of left eye of rabbit. Observations
were made aftcr 5. 10, and IS min , respecti ve ly of
instillation and eyes were observed for redness ,
swel lin g, wateri ng, ctc. Th e ri ght eye served as control.
REDKAR el at.: DEXTR AN -
HPM C EYE DROPS AS ARTI FICIAL TEA RS
Results And Discussion
Borax and boric acid buffer were used as the vehicle with sodium chloride as the tonicity adju stin g
agent. Formul ati ons containing HPC (Formul ati ons
B and E) were found to have relati ve ly hi gh viscos iti es, which made in still ati on into the eye di fficul t. Formul ation containin g onl y dex tran (Formu lati on C) had very low viscos ity, whi ch was in creased in combin ati on with HPM C.
Formulation D was se lected because its vi scos ity
was optimum as compared to other formulati ons.
Al so, formul ation D was abl e to produce a stabl e
tear film . As seen in Table I the ch osen fo rmul ati on
passed the evalu ation tests for clarity, pH , viscos ity,
and spec ifi c grav ity.
In terms of clarity of the fo rmul ati on, pH, specific gra vity, viscosity and per cent drug content,
the fo rmulati on was fo und to be stabl e durin g acce lerated therm al studi es for the test peri od of six
months.
It was observed th at li ght had no detrimental effect on the formul ation. It is reported th at so me fracti ons of dextran may adopt certain degree of crystallinity when stored at accelerated temperatu re.
However, none of the vial s showed any type of precipi tation or fl ake fo rmati on.
After autocl av in g the HPMC was fo und to precipitate at hi gh temperature. Hence the vials mu st
be shaken in order to redi sperse the HPMC. At roo m
temperature the HPMC goes into so luti on and vials
remain clear.
I Oj l
The results obtained with Schirmer's test revealed
that the wettin g effect by MOISOL® on eye was
maintained for one-and- a-h alf hour, whereas the
wettin g effect produced by deve loped formul ation
was maintained fo r more th an 2 h. Al so the amoun t
of wettin g was more with deve loped formul ation
th an that with MOISOL®.
Ocul ar irritati on studi es revea led th at none of th e
rabbits showed any type of ocul ar irritati on towards
fo rmulati on as well as towards MOISOL®.
Conclusion
Thi s study was aimed at developin g a suitab le
artificial tear fo rmul ati on fo r the treatment of dry
eye syndrome. An ophthalmic soluti on was prepared
by usin g HPM C and dext ran po lymers, which
showed better fi1m formin g properti es th an the marketed preparati on.
The in stillati on of normal saline for dry eyes is of
very limited va lue. Other tear substitutes include
vitamin A deri vati ves, viscoelastic age nts, mucolyti c agents, and lipid containing fo rmul ati on. However, arti ficial tears, due to better tear film fo rming
capac ity, ease of fo rmul ati on, ease of insti Il ation and
better pati ent co mpli ance may be considered as th e
mos t suitabl e treatment for dry eye syndrome.
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D & A min P D. Dmg Dev Illd Pha rlll , 23 ( 1997) 405.
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:\
Haberg G P & Berens C, Alii } Ophthallll ol, 51 ( 1961 ) X-HJ.