Granisetron is a drug used to treat nausea and vomiting after chemotherapy. Crystallization of drug is always a major concern in the transdermal drug delivery system. In view of consistent biopharmaceutical performance, monitoring and controlling the crystallization during product development and shelf life is very important. The need was felt to have an accurate method for determination of crystallinity in transdermal patches.The present study is about development and validation of a quantitative X-ray diffraction method for the determination of the extent of crystallization of the drug in transdermal formulation of Granisetron. Specimens of different physically spiked concentrations were carefully prepared accurately by weighing and distributing crystalline active pharmaceutical ingredient (API) onto placebo liner patches, pasted on Silicon low background sample holder (diameter of 24.5 mm, made up of Si crystal). All the specimens thus prepared were scanned using optimized instrumental parameters while enabling specimen rotation during the diffraction analysis to ensure homogeneous exposure to the incident X-rays. Using this novel approach, limit of detection 

A, Ravikiran

B, Rajendar

Ch, Praveen

M, Arthanareeswari

P, Kamaraj

Pavan, K V

Advanced Research Journals

  
 
International Journal of Drug Delivery 4 (2012) 492-497 
http://www.arjournals.org/index.php/ijdd/index 
 
Original Research Article 
             
An approach to determine crystalline content of Granisetron in transdermal patches using 
X-ray diffraction technique 
Pavan K V*1, Arthanareeswari M1, Ravikiran A1, Kamaraj P1, Praveen Ch1, Rajendar B1 
 
*Corresponding author: 
 
Pavan K V 
1Department of Chemistry, SRM 
University, SRM Nagar, Kattankulathur-
603203,Kancheepuram District, 
Tamilnadu, India 
 
 
 
 
 
 
 
 
 
 
 
 
A b s t r a c t  
Granisetron is a drug used to treat nausea and vomiting after chemotherapy. Crystallization of drug 
is always a major concern in the transdermal drug delivery system. In view of consistent 
biopharmaceutical performance, monitoring and controlling the crystallization during product 
development and shelf life is very important. The need was felt to have an accurate method for 
determination of crystallinity in transdermal patches. 
The present study is about development and validation of a quantitative X-ray diffraction method for 
the determination of the extent of crystallization of the drug in transdermal formulation of 
Granisetron. Specimens of different physically spiked concentrations were carefully prepared 
accurately by weighing and distributing crystalline active pharmaceutical ingredient (API) onto 
placebo liner patches, pasted on Silicon low background sample holder (diameter of 24.5 mm, made 
up of Si crystal). All the specimens thus prepared were scanned using optimized instrumental 
parameters while enabling specimen rotation during the diffraction analysis to ensure homogeneous 
exposure to the incident X-rays.  
Using this novel approach, limit of detection of about 2% (weight/weight) was achieved for the drug 
crystalline content. The validation results indicated excellent linearity between diffracted peaks 
response (net area) and spiked concentration of crystalline drug with a correlation value of 0.9991, 
Accuracy with the recovery values well within the range of 95% to 110% and precision having RSD 
values lesser that 2% (at limit of quantification). The method can be adopted by any quality control 
lab for its intended purpose. 
Keywords: Crystallinity, Amorphous, X-Ray Diffraction, Placebo, Transdermal. 
 
 
 
Introduction 
Transdermal drug delivery systems (TDS) are polymeric patches 
containing dissolved or dispersed drug that can deliver a drug at 
relatively constant rate to human body. TDS offers several 
important advantages over traditional approaches, which includes 
longer duration of action resulting in reduced dosing frequency, 
improved bioavailability and flexibility of terminating the drug 
administration by simply removing the patch from the skin and 
improved patient compliance and comfort via non-invasive, 
painless and simple application [1]. Some of the disadvantages of 
TDS are like local irritation at the site of application, itching, local 
edema and erythema can be caused by the drug, the adhesive, or 
other excipients in the patch formulation [2, 3]. One of the most 
successful advancements in TDS, is crystal reservoir technology 
has resulted in smaller patches with a more controlled and 
sustained drug release. This efficient drug delivery technology 
may minimize the amount of active pharmaceutical ingredient 
(API) required. This efficient way of releasing a drug is based on 
the over saturation of an adhesive polymer with medication, thus 
forcing a partial crystallization of the drug. The presence of both 
molecular solute and solid crystal forms allow for a considerably 
higher concentration and consistent supply of drug in each patch. 
As the skin absorbs the molecular solute, crystals re-dissolve to 
maintain maximum thermodynamic activity at the site of contact 
[4-6]. 
Drug crystallization has been reported in many Transdermal 
matrix systems [7-10] as well as other types of drug delivery 
systems [11-17]. An illustration was represented in Figure-1. The 
presence of crystals in a transdermal patch might significantly 
affect the permeation of the drug through the patch, if dissolution 
of drug is the rate controlling step in the mass transfer process 
compared to the diffusion rate. Examples of decreased 
bioavailability were reported in the crystallization of Nifedipine co-
ISSN: 0975-0215 
  
This work is licensed under a Creative Commons Attribution 3.0 License.  
Pavan et al. International Journal of Drug Delivery 4 (4) 492-497 [2012] 
 
PAGE | 493 |
 
precipitated with Polyvinylpyrrolidine (PVP) [14], Indomethacin 
dispersed in polyacrylate adhesives stored over a period of a 
period of six months at room temperature with moderate relative 
humidity [1,10]. In the present work, Granisetron transdermal 
patches, contains API in amorphous state were considered. Drug 
is often used in amorphous state especially in transdermal 
patches because the amorphous solid state has a higher 
dissolution rate, higher chemical reactivity and higher water vapor 
sorption than the crystalline state. This is due to increased free 
volume, molecular mobility and the enthalpy of the amorphous 
state [18]. These properties can have benefits. For example, rapid 
formation of solution is sometimes desirable to achieve a high 
efficacy and a rapid absorption rate that may increase the 
bioavailability of the drug [19]. 
 
 
Figure 1: An illustration demonstrating crystallization in 
Transdermal patches. 
 
The biopharmaceutical classification system (BCS) divides drugs 
into four classes depending on drug product in vitro dissolution 
properties and in vivo bioavailability [20]. Poor dissolution of drug 
may be the rate limiting step to absorption and hence to 
bioavailability of drug. More than 40% of potent new APIs suffer 
from poor solubility and thus pharmaceutical companies are 
interested in the amorphous state [21]. So, determination of 
degree of Crystallinity in a converted amorphous transdermal 
patch is crucial and plays a key role in the stability studies and 
controlling the factors affecting the conversion. To the best of our 
knowledge, none of the reported procedures describe method for 
the determination of degree of crystallinity in converted 
transdermal patches. Thus, an attempt was made to develop and 
validated a new method for the determination of degree of 
crystallinity in converted transdermal patches. Granisetron 
Transdermal patches are used for this exertion. 
The API used for the study is Granisetron Hydrochloride. 
Intravenous chemotherapy in patients suffering from cancer 
requires the co-administration of several medications to prevent 
severe side effects that are enough to deter patients from 
continuing therapy [22]. Granisetron Hydrochloride is a selective 
5-HT3 receptor antagonist. It is also an effective and post-
operative nausea and vomiting in adults and children. The 
chemical name of Granisetron Hydrochloride (Molecular structure 
represented in Figure-2) is 1-Methyl-N-[(3-endo)-9-methyl-9-
azabicyclo[3.3.1]non-3-yl]-1H-indazole-3-carboxamide 
hydrochloride. Molecular Formula is C18H24N4O.HCl; 
C18H25ClN4O and molecular weight is 348.87 [23]. 
 
 
 
Figure 2: Molecular structure of Granisetron HCl. 
Materials and Methods 
Materials 
Crystalline Granisetron Hydrochloride API, Amorphous 
Granisetron Patch (6.99cm2) and Placebo patch (6.99cm2). 
Silicon low background sample holder (External diameter 51.5 
mm, internal diameter 24.5 mm, made-up of Si crystal) sample 
holders were used for this study. 
Methods 
Specimen preparation (Spiked standards) 
High Sensitive Microbalance (Mettler Toledo XP2U, Maximum 
2.1g and Minimum-1μg) was used to prepare all the required 
spiked concentrations. The different Spiked Concentrations were 
prepared by accurately weighing required amount of crystalline 
API of Granisetron Hydrochloride followed by spreading uniformly 
on to the Silicon Low background sample holder and pasted 
Placebo patch after removing liner. In the Transdermal Patches 
formulation, each patch of area 6.99cm2 contains 3.5mg of the 
API. So the required concentrations were prepared accordingly. 
The weights of the API taken for the required concentration 
preparations are listed in the below Table 1. 
Powder X-ray diffraction analysis 
The diffraction patterns of the spiked concentrations and of 
crystalline API were collected using Bruker Axs-D8 ADVANCE 
with Cu Anode and Lynx Eye detector. Each sample was scanned 
from 13Ĉ to 22Ĉ 2theta, with step size of 0.01Ĉ and time per step of 
3 seconds. The Instrument was operated at 40kV Generator 
Voltage and 40mA Generator current. Variable divergent slit and 
Anti scattering slit were used of V20mm; Nickel filter was used in 
secondary beam path as K-beta filter. Eva Software was used for 
data processing and evaluation.  
 
Pavan et al. International Journal of Drug Delivery 4 (4) 492-497 [2012] 
 
PAGE | 494 |
 
Table 1: Preparation of spiked concentrations: actual weights of 
crystalline API transferred and corresponding crystallity value 
calculated against 3.5mg of the API per patch. 
Sl. No Weight of Crystalline 
API transferred (mg) 
Actual concentration   
(% Weight/Weight) 
1 0.075 2.1 
2 0.145 4.1 
3 0.271 7.6 
4 0.357 10.1 
5 0.529 14.9 
6 0.707 19.9 
Results and discussions 
The diffraction pattern of crystalline API and overlaid diffracted 
patterns of spiked concentrations are represented in Figure-3 and 
Figure-4 respectively. The sum of net area values (in cps x 
degree) of characteristic diffraction peaks (at about 13.9Ĉ, 14.3Ĉ, 
15.3Ĉ, 16.1Ĉ, 17.3Ĉ, 18.2Ĉ and 18.9Ĉ 2theta) of crystalline API for 
different spiked concentration were listed in Table-1. A linear 
graph was obtained by plotting concentrations versus net area. 
The linear equation was supported by high correlation value (R2 
value is 0.9991). 
Validation results 
The limit of detection (LOD) for was determined by signal to noise 
ratio and the value found to be about 2.0% (weight/weight) for 
crystalline API in patches. To check accuracy and precision of the 
method, the spiked concentrations were prepared at the 
concentrations of 2% and 5% (weight/weight) in triplicate, the 
same were analyzed and data evaluated, the results are compiled 
in Table-3 and Table-4 along with the mean and percent relative 
standard deviation (% RSD). The overlaid diffractograms at Limit 
of Detection Level and Limit of Quantification Level are shown in 
the Figure-5 and Figure-6 respectively. It was observed that the 
calculated wt% values predicted by X-ray diffraction are in good 
agreement with the actual wt%. The low %RSD indicates that the 
method is precise and reproducible 
 
Table 2: Prepared spiked concentrations and sum of the net area 
values 
Sl.No 
Concentration of the 
spiked standard 
(weight/weight) 
Sum of the net area values 
of the characteristic  peaks 
of crystalline API (cps x 
degree) 
1 2.1 0.65 
2 4.0 0.913 
3 7.7 1.494 
4 10.1 1.786 
5 14.9 2.593 
6 19.9 3.29 
  
 
Table 3: Accuracy and reproducibility in quantitative measurement at limit of detection (LOD) 
Actual wt%  
(calculated from weight of API 
spiked) 
Calculated wt% Net Area (Cps x deg) %Recovery 
2.11 2.08 0.635 101 
2.19 1.99 0.622 110 
1.93 1.77 0.588 109 
Mean 1.95 0.615 
 Standard deviation 0.162 0.024 
%RSD 8.3 3.9 
 
Table 4: Accuracy and reproducibility in quantitative measurement at limit of quantification (LOQ) Level 
Actual wt%  
(calculated from weight of API 
spiked) 
Calculated wt% Net Area (Cps x deg) %Recovery 
5.13 5.06 1.081 101 
5.93 5.15 1.095 96 
5.08 4.97 1.067 102 
Mean 5.06 1.081 
 
 
 
Standard deviation 0.094 0.014 
%RSD 1.8 1.3 
Pavan et al. International Journal of Drug Delivery 4 (4) 492-497 [2012] 
 
PAGE | 495 |
 
 
Figure 3: Diffraction pattern of Granisetron crystalline API: Characteristic peaks used for quantitative analysis are labeled with respective peak 
position values. 
 
Figure 4: Overlaid diffraction pattern of different spiked concentrations of crystalline API in Placebo patch: Incremental change can be seen at 
the characteristic peak positions. 
 
In
te
ns
ity
0
200
400
2-Theta - Scale
13 14 15 16 17 18 19 20 21 22
A
=1
3.
89
2 
°
A
=1
4.
32
0 
°
A
=1
5.
28
9 
°
A
=1
6.
12
7 
°
A
=1
7.
34
0 
°
A
=1
8.
24
4 
°
A
=1
8.
91
7 
°
In
te
ns
ity
0
20
40
60
80
2-Theta - Scale
13 14 15 16 17 18 19 20 21 22
Placebo Patch
Amorphous Patch
2.1% Crystalline Spiked
4% Crystalline Spiked
7.7% Crystalline Spiked
10% Crystalline Spiked
15% Crystalline Spiked
20% Crystalline Spiked
Pavan et al. International Journal of Drug Delivery 4 (4) 492-497 [2012] 
 
PAGE | 496 |
 
 
Figure 5: Precision and Reproducibility at LOD Level 
 
Figure 6: Precision and Reproducibility at LOQ Level  
Conclusion 
In this work, we have reported a method to determine degree of 
crystallinity in converted amorphous transdermal Patches using X-
ray diffraction technique. The results obtained in this study clearly 
demonstrate the potential of X-ray diffraction technique, which  
 
 
 
proves to be relatively simpler and better technique for the 
crystallinity determination in transdermal patches. The method  
can be adopted by any quality control laboratory for its intended 
purpose without any major changes  
Acknowledgements 
In
te
ns
ity
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
2-Theta - Scale
13 14 15 16 17 18 19 20 21
Spiked at LOD, Preparation-1
Spiked at LOD, Preparation-2
Spiked at LOD, Preparation-3
In
te
ns
ity
0
20
40
2-Theta - Scale
13 14 15 16 17 18 19 20 21 22
Spiked at LOQ level, Preparation-1
Spiked at LOQ level, Preparation-2
Spiked at LOQ level, Preparation-3
Pavan et al. International Journal of Drug Delivery 4 (4) 492-497 [2012] 
 
PAGE | 497 |
 
The author wish to thank Department of Chemistry, SRM University for their excellent guidance and support.  
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An approach to determine crystalline content of Granisetron in transdermal patches using X-ray diffraction technique

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An approach to determine crystalline content of Granisetron in transdermal patches using X-ray diffraction technique

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