1. PREDICTION OF DRUG CONTENT IN INTACT TABLETS BY NEAR - INFRARED SPECTROSCOPY
,Branko Vranic1, Nada Tarek2 ,V. Frost 3, G. Betz1
1Industrial Pharmacy Lab, Department of Pharmaceutical Sciences, University of Basel, Switzerland
2Future University in Egypt
3Büchi Laboratechnik AG, Flawil, Switzerland
Materials and Methods
Results Summary
Introduction
NIR Spectroscopy
Near infrared spectroscopy (NIRS) belongs to vibrational spectroscopy. It covers the wavelength region of 750 – 2500 nm. The NIR signal is a consequence of the absorbance of light due to molecular vibrations (overtones and combinations of fundamental mid – IR vibrations) of hydrogen bonds like C-H, N-H, O-H, S-H. The benefits of NIRS are well recognized. It is fast, nondestructive, noninvasive analytical technique requiring minimal or no sample preparation. It is able to analyze various pharmaceutical dosage forms. Apart from the number of applications in drug development and quality control, NIRS has proved its efficiency as Process Analytical Technology (PAT) tool in monitoring the critical-to-quality attributes (CQAs) during the manufacturing process.
Chemometrics
NIR spectra are composed of broad and overlapping absorption bands carrying physical and chemical information of analyzed sample. Multivariate character and poor selectivity of spectral data imposes requirement for the use of mathematical and statistical methods for extraction of relevant data and reduction of interfering physical parameters. Most commonly employed chemometric technique is partial least squares regression (PLS). Together with the wavelength selection and mathematical pretreatments of spectra, it is used to establish a ralation between the spectral data and reference values and finally to construct a prediction model.
Process Analytical Technology (PAT)
Recently, the concept of Process Analytical Technology (PAT) was introduced in the FDA`s Guidance for Industry. PAT enables quality assurance of a whole batch by monitoring the critical-to-quality attributes (CQAs) during manufacturing process. NIRS is extensively used to monitor CQAs in different manufacturing processes due to its speed and nondestructive character.
NIR sampling modes
Recent studies in our research group were aimed to compare diffuse reflectance and transmittance mode. It was shown for a tablet with 10 mm diameter that central 5 mm carry 77% of the transmittance signal (38% of the whole surface) and the peripheral 5 mm 23% of the signal (62% of the whole surface). Study of the penetration depth of diffusely reflected NIR radiation showed that 0.07 and 0.21 mm thick tablet coating layer contributed to 50 and 90% signal drop respectively1. Conclusions from this study suggest that diffuse transmittance mode is more suitable for tablet drug content prediction and diffuse reflectance mode for studying polymer coating thickness, homogeneity and drug content in the coating layer.
Quantitative NIRS for tablets
NIRS is commonly employed for prediction of drug content in intact tablets. Tablets are scanned by NIR spectrometer, followed by wet lab reference analysis. Reference values of drug content are assigned to corresponding spectra and finally after mathematical pretreatment of spectra and calibration wavelength selection, PLS regression is applied in order to link the spectral and the reference data and to develop a prediction model.
The aim of the present work was:
Development of a model for caffeine content prediction in intact tablets
Evaluation of the effect of sample size and variability of compression force on the robustness and predictive ability of the developed calibration models
Comparison between diffuse reflectance and transmittance mode
Tablet formulation
Caffeine, 20 – 30% m/m (active pharmaceutical ingredient)
Microcrystalline cellulose, 66 – 76% m/m (filler)
Sodium carboxymethyl starch (Primojel®), 3% m/m (disintegrant)
Magnesium stearate, 1% m/m (lubricant)
Direct compression tabletting
PressterTM – tablet press simulator (MCC)
10 mm flat face punch
Simulated press: Korsch PH336 rotary press,
36 stations, TPH
Gap size range: 2.34–3.58 mm (200–100 MPa)
29 batches, 340 tablets
200 mg tablets
NIRS measurements
Büchi NIRFlex N-500 FT spectrometer with reflectance and transmittance module
Büchi NIRCal 5.2 Chemometrics software
Referencing
Reference analysis was done by validated UV-spectrometric method using Beckman DU530 UV/VIS spectrophotometer.
The first calibration models were developed with fixed compression force tablets (12.5 kN which corresponds to 150 MPa compression pressure) in diffuse reflectance and transmittance mode. Obtained models were validated with 3 independent test sets compressed with 150, 175 and 125 MPa respectively.
After the inclusion of additional samples, developed models were able to predict test samples with lower SEP, showing better performance. Transmittance mode was shown to be more sensitive to variations in compression force. Addition of samples with variable porosity increased the robustness of the prediction models in terms of compression force, especially with transmittance mode. After the external validation of the developed models with 3 independent sample sets all above stated was confirmed.
Single compression force
Different compression force
Reflectance
mode
Transmittance
Mode
Parameter
C-set
V-set
S-set
Precision
SEC SEP
SEC SEP
SEC SEP
SEC SEP
Accuracy(BIAS)
Regression
Coefficient
Q-value
Consistency
97.171
99.671
102.67
EXTERNAL VALIDATION
RMSEP (test set) 0.
0.9646
Fig.2 The PressterTM
Fig.3 Station
Transmittance module
Polarization interferometer
Fig.4 NIRFlex N-500
Reflectance module
UV assay vs NIR prediction
Results: single compression force
DIFFUSE TRANSMITTANCE
DIFFUSE REFLECTANCE
23% of signal
62% of area
77% of signal
38% of area
% drug
tablet number
Table 1. Calibration parameters
tablet side view
tablet top view
Fig.5 effect of the sample size on NIR prediction (above)
Fig.1 scanned portions of a tablet
UV assay vs NIR prediction
Fig.4 Calibration models in reflectance (left) and transmittance mode
% drug
Results: variable compression force
References
1. M. Saeed, S. Saner, J. Oelichmann, H. Keller, G. Betz. Assessment of diffuse transmission mode in near-infrared quantification - part I: The press effect on low-dose pharmaceutical tablets. Journal of Pharmaceutical Sciences. (early view)
tablet number
Fig.6 effect of the variable compression F on NIR prediction
Objectives
The first calibration models were extended with variable compression force tablets spectra (100 – 200 MPa) in order to develop robust models, less sensitive to variations in porosity (density, thickness).
Conclusions
↑ number of samples » ↑ predicting ability of the developed model
Inclusion of variable porosity tablets gave ↑ robustness of the model
Diffuse transmittance mode showed better performance
NIRS was proved to be an adequate alternative to wet-lab assay
Fig.4 Calibration models in reflectance (left) and transmittance mode