Indomethacin
Indomethacin
Indomethacin
ACTA
HELWI'IAE
ELSEVIER Pharmaceutics Acta Helvetiae 70 (1995) 307-313
Abstract
The sustained release properties of an indomethacin hard-gelatin capsule formulated with saturated polyglycolysed glycerides
(Gelucire@) were demonstrated in vivo. Indomethacin was selected as a model drug with very poor solubility in water and acidic media.
It is known to exhibit high intersubject variability because of enterohepatic circulation. The formulation, which in vitro showed an
erosion-controlled release, was compared in six human volunteers in the fed state by using a randomized cross-over design, to a standard
multiple-unit diffusion-controlled pellet capsule. Close action period values (time duration with plasma levels higher than 0.5 pg/ml)
were found for the test and the reference formulation (5.2 and 5.7 h). The time to reach peak t,, appeared slightly shorter for the test
preparation (1.75 h) than for the reference formulation (2.67 h), but the difference was not statistically significant because of the high
intersubject variability (non-parametric Wilcoxon matched pair test). Again, due to the small number of subjects entered in the study
(insufficient for a real bioequivalence study) equivalence could not be accepted in terms of extent and rate of absorption based on the
decision procedures involving the 90% confidence interval and the two one-sided t-tests. The mean maximum plasma concentrations
C max were 3.35 and 2.82 pg/ml for the test and the reference formulation respectively, with the corresponding values of the area under
the plasma concentration-time curve AUC amounting to 10.14 and 11.38 pg h/ml. However, a simulation on 24 subjects (3 repetitions
of the same data) would lead to bioequivalence of the two preparations. As for other corrosion-controlled forms, drug release from the
proposed Geluciree formulation was very sensitive to hydrodynamic conditions, leading to poor in vitro-in vivo correlation, when
comparison is made with a reference formulation characterized by a diffusion-controlled release. Finally, it was concluded that
erosion-controlled release formulations are especially suitable for drugs, such as indomethacin, that have low solubility in water or acidic
media. More generally, sustained release hard gelatin capsules with thermosetting excipients is very versatile and their preparation is very
straightforward.
Keywords: Indomethacin; Pharmacokinetics, zero-order; Bioavailability; Hard-gelatin capsule; Erosion-controlled release; Saturated polyglycolysed
glycerides
1. Introduction
steps. By contrast, monolithic systems such as lipid sys- release, formulated with Gelucire@ excipients. As refer-
tems are straightforward to prepare. In the molten state, ence, a sustained-release multiple-unit hard-gelatin capsule
these formulations can be directly filled into hard-gelatin product was selected.
capsules, bearing in mind that capsule binding may be
necessary. The principle of thermosetting formulations has
already been studied in early papers (Cuint et al., 1978; 2. Materials and methods
Frangois, 1979; Walker et al., 1980), and in particular from
our investigation on the use of saturated polyglycolysed 2.1. Materials
glycerides (Eur. Ph.) commercially available as Gelucire@
(Doelker et al., 1983; Bemasconi et al., 1985; Buri et al., The sparingly soluble model drug indomethacin used in
1985;Doelker et al., 1986; Buri et al., 1988; Vial- the preparation of the capsules (lot # 32/83M-1M) was
Bemasconi et al., 1987). Gelucire@ excipients are total or supplied by Selectchemie (Ziirich, Switzerland), with a
partial glycerides (triacylglycerols) and polyethylene gly- volume-surface diameter of 10 pm. The Geluciree excipi-
co1 mono- and diesters of different molecular masses. The ents (Gattefosse, Saint-Priest, France) selected were grades
various grades are characterized by their hydrophile-lipo- 46/07 (lot # 1411) and 33/01 (lot # 3413). For each
phile-balance (HLB) value and melting point which leads grade the first two figures characterize the melting point
to a specific behaviour when placed in the gastrointestinal and the last two the HLB value (Waginaire and Glas,
fluids in respect of hydrodispersibility, melting and floata- 1981).
bility (Doelker et al., 1983, Doelker et al., 1986). As for The reference formulation was Indocid@-Retard 75 (lot
the in vitro sustained-release characteristics, we have shown # 718481T, Merck Sharp and Dohme-Chibret, Zurich,
that careful selection and proportion of the Gelucire@ Switzerland). Each capsules contained 25 mg of immediate
grades can lead to diffusion- or erosion-controlled matrix release pellets and 50 mg of pellets coated with an inert
formulations (Buri et al., 1985). Thus, a diffusion-con- vinyl polymer for ensuring a slow release over approxi-
trolled system was obtained with the Gelucire@ grade mately 12 h.
46/07, 48/09 or 62/05 containing 660 mg lithium sulfate
(square root of time kinetics), all three Gelucire grades 2.2. Preparation of the capsules
remaining inert in the aqueous environment at 37°C. On
the contrary, erosion was proved to control the release of The nominal composition of the test capsules was the
indomethacin (75 mg) when the dispersible Gelucire@ following: indomethacin 75 mg, Gelucire@ 46/07 55 mg
33/01 was added to the inert Gelucire@ 46/07. Since and Gelucire@ 33/01 102 mg. The drug was dispersed in
then, several studies on Gelucire@-based capsules have the Gelucire@ excipients heated at 55°C and the mixture
been published, most of them concerned with in vitro was manually filled into transparent size 4 Snap-Fit TM
release. Very few human studies using such systems have hard-gelatin capsules (Capsugel, Basle, Switzerland) using
been reported. Djimbo et al. (1984) showed some retarda- a syringe. The weight and content coefficients of variation
tion in the urinary excretion of total salicylate when ad- were 1.6 and 4.7%, respectively.
ministering capsules of aspirin mixed with Gelucire@ We verified that the formulation could be prepared
50/13. Also with aspirin Mathis and Heimendinger (1989) using an industrial filling machine (Zanasi Nignis 25000,
observed the same pattern using salicylate salivary data Bologna) equipped with a volumetric dosing pump.
and capsules prepared with a mixture of Gelucire 48/09
and 44/14. We demonstrated, in a comparative study with 2.3. In vitro drug release testing
a commercially available compressed hydrophilic tablet
matrix, that fairly uniform drug plasma levels were also The USP paddle apparatus was used in which the
observed with two different lithium sulfate capsule formu- capsule was held in a spiral. Two different release media
lation based on Gelucire@ (Vial-Bernasconi et al., 1987; were used, because release from both formulations proved
Buri et al., 1988). Dennis et al. (1988) obtained similar to be highly pH dependent. Thus, the release media were
results with ketoprofen formulated with Gelucire@ 50/02 the pH 6.2 phosphate buffer of the ‘Indomethacin Ex-
and 50/13. The in vitro release profiles of all these tended-release Capsules’ USP monograph and the pH 7.2
formulations were either not characterized or found to be phosphate buffer of the ‘Indomethacin Capsules’ mono-
diffusion-controlled. graph. For sake of validity of the comparison, the same
The purpose of this work was to demonstrate in vivo, agitation rate (75 rpm) and volume of release medium
by measuring plasma levels, the sustained release proper- (1000 ml) were used in the two cases. The volume larger
ties of an indomethacin capsule with erosion-controlled than those specified in the monographs was judged neces-
A.-C. Vial-Bernasconi et al. /Pharmaceutics Acta Heluetiae 70 (1995) 307-313 309
sary because the ‘sink’ conditions were not fulfilled in the with a full scale deflection of 0.01 aufs. The injected
pH 6.2 phosphate buffer (solubility of about 0.3 mg/ml volume was 20 ~1, and the run time was 12 min.
vs. 1.0 mg/ml at pH 7.2). Samples were taken at various Phenylbutazone (Aldrich Chemicals, Steinheim, Germany)
time intervals and assayed for indomethacin spectrophoto- was used as internal standard.
metrically at 320 nm. Results are means of six replicates. The procedure was the following. A 500 ~1 aliquot of
plasma was pipetted into a glass-stoppered tube, along
2.4. In vivo experiment with 50 ~1 of a 2 mg % methanolic solution of phenylbu-
tazone, 1 ml of pH 5.0 Sorensen citrate buffer and 1 ml of
Six healthy male volunteers, after giving their informed
distilled water. The mixture was vortexed for 10 s and
written consent, were entered into the study. Their age
extracted using 3 ml diethyl ether by shaking the tube for
ranged from 21 to 35 years, and their body weight from 62
10 min. After separation, the organic phase was transferred
to 78 kg, not deviating by more than 10% from the ideal
to a haemolysis tube and evaporated to dryness under
weight for height according to the Metropolitan Life Insur-
vacuum. The residue was dissolved in 200 ~1 of mobile
ance Company Bulletin 1983. Each subject was required to
phase through vortexing and 20 ~1 of this solution were
be free of cardiovascular, hepatic, renal, or gastrointestinal
injected. The extraction yields were 99% for indomethacin
diseases and had no history of drug or alcohol abuse. In
and 95% for phenylbutazone. The respective retention
addition, the blood pressure, electrocardiogram and clinical
times were 7 and 9 min. The quantification limit was 0.25
analyses were within normal ranges and subjects were
pg/ml plasma and the linearity was verified up to 4
asked to abstain from taking any other drugs for 15 days
pg/ml range.
prior to completion of the study. They were also required
to refrain from consuming alcoholic or caffeine-containing
2.6. Pharmacokinetic parameters and statistical analysis
beverages from 72 h before the administration until after
the collection of the last blood sample.
Calculation of the pharmacokinetic parameters and the
Subjects were randomly assigned to receive, in a fed
statistical analysis were performed using a Siphar pro-
state, in a crossover design either one 75 mg sustained
gramme (Simed, Creteil, France). The following parame-
release test capsule or one 75 mg reference capsule, to-
ters were estimated from the plasma concentration-time
gether with 150 ml water. A light continental breakfast
profile:
was taken 1 h before administration, a standardized lunch
the lag time, tlag, i.e., the time elapsed from the inges-
(1000 kcal) 4 h later, then a standardized dinner (970 kcal)
tion of the form to the first measurable concentration
10 h after. There was a l-week interval between each
was evaluated directly from the plasma concentration;
treatment period.
the time at which the concentration is maximum, t,,,,
2.5. Blood sample collection and analysis or time to peak, and the maximal concentration, C,,,,
were also estimated directly from the plasma concentra-
Blood samples (10 ml) were taken at time 0 h and at tion;
0.33, 0.67, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10, 12, 24 and 36 h. the area under the plasma concentration up to the last
The blood samples were centrifuged immediately and the measured concentration, AUC(O-24), was calculated
plasma was stored at - 20°C until analysis. Plasma (500 using the trapeizoidal rule;
~1) was assayed for indomethacin using a modification of the area under the plasma concentration-time curve
published HPLC methods (Yi-Hung Tsai and Shun-Ichi extrapolated to time infinity, AUC, was determined by
Naitu, 1981; Turlier, 1985). adding to the appropriate AUC(O-24) value the quo-
The apparatus used was a Waters MS10 high-pressure tient of the estimated last plasma concentration and the
liquid chromatograph equipped with a WISP 710B auto- appropriate value of k,;
matic injector (Millipore Corp., Milford, USA), an Applied the terminal elimination rate constant, k,, was calcu-
Biosystems 757 UV detector (Warrington, UK) and a lated by least squares regression from the slope of the
Shimadzu CRGA integrator (Tokyo, Japan). A Merck linear segment of the log concentration vs time profile;
. . .
LiChrospher@ 100 R-18 (5 pm) precolumn and a Merck the ehmmatron half-life, t,,,, was calculated from the
LiChrospher @ 100 RP-18 (5 pm) 12.5 cm column quotient of 0.693 and k,;
(Darmstadt, Germany) were used. The mobile phase con- the mean residence time, MRT, was calculated as de-
sisted of an acetonitrite/0.03% acetic acid (48:42 v/v) scribed by Cutler (1987);
mixture. The operating temperature was ambient, and the the action duration, t,, was taken as the period over
flow rate was 2 ml/min with a pressure of 1200 psi. The which the plasma concentration was higher than 0.5
column effluent was monitored continuously at 254 nm pg/ml.
310 A.-C. Vial-Bernasconi et al. /Pharmaceutics Acta Helvetiae 70 (1995) 307-313
Table 1
Pharmacokinetic parameters obtained after oral administration of the test formulation (T) and the reference formulation (R) to six subjects
Subject no. Form riag (h) r,,, (h) =,,,a, AUC (O-24) AUC k, (l/h) tr/z (h) MRT (h) t, (h)
( pg/mt) ( pg h/ml) ( Kg h/ml)
Mean T 0.89 1.75 3.35 9.17 10.14 0.362 2.34 3.88 5.19
R 1.22 2.67 2.82 9.34 11.38 0.239 4.99 6.33 5.71
SD. T 0.50 0.76 1.19 0.77 1.33 0.185 1.12 1.55 2.00
R 0.50 1.33 0.98 1.72 2.97 0.240 2.90 1.89 1.28
C.V. (o/o) T 56.2 43.3 35.5 8.3 13.6 51.3 47.7 39.9 38.6
R 40.9 49.8 34.8 18.4 26.1 100.4 58.1 29.9 22.5
Table 2 particularly suitable for drugs which are very poorly solu-
Summary of bioequivalence attributes
ble in water or acid media.
Param- A.M.R. a 90% C.I. b G.M.R.’ 90% C.I. b tl t2 More generally, formulating with saturated polyglycol-
eter lower limit upper limit
ysed glycerides (Gelucire@) and the one-step manufacture
c max 1.305 0.727 1.178 1.908 1.708 d 0.264 d process of these hard gelatin capsules with thermosetting
AUC 0.933 0.728 0.910 1.138 1.227 d 3.027 e excipients are claimed to offer many potentialities.
a Arithmetic mean of ratios.
b Confidence interval.
’ Geometric mean of ratios. Acknowledgements
d Not significant.
e p < 0.05.
The authors are grateful to Gattefosse S.A. (J.-P.
Lafor&t) and Capsugel S.A. (Dr E.T. Cole) for supporting
this work.
(1985). The two values observed did not differ signifi-
cantly (paired-sample t test). Finally, taking 0.5 pg/ml as
the threshold concentration for pharmacological action, the
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