Fikri Alatas, et al.
INTERACTION BETWEEN BETAMETHASONE-17-VALERATE
Interaction Between Betamethasone-17-Valerate...
In pharmaceutical sciences, the most common interaction is eutectic mixture. Eutectic is a mixture of chemical compounds or elements that has a lower melting point than any its single pure component. Normally, the eutectic formation cause increasing of moisture in the powder mixture and very rare followed by changing of biological effect. Such condition can be easily overcome by addition some amounts of adsorben. Whilst, there are some interaction that almost similar with eutectic phenomenon be able to influence the efficacy, even toxicity of drugs combination. In general, there are two types of physical interactions or intermolecular interactions, namely: 1) conglomerate without mixed crystal formation and 2) conglomerate with mixed crystal formation. All of them showed almost similar phenomenon, that is melting point decreasing.
Corticosteroids are frequently used as topically drugs. Despite of their demonstrated effectiveness for the treatment of psoriasis and atopic dermatitis, topical corticosteroids are associated with various side effects that may limit their use (Del Rosso and Friedlander, 2000; Wiedersberg et al., 2008). Betamethasone-17-valerate (BV) (Fig. 1a) is the gold standard of these agents and serves as a reference in the clinical studies for the registration of new glucocorticosteroids (Sivaramakrishnan et al., 2004). It is a medium potency glucocorticoid, lacking mineralocorticoid properties, currently available in topical dosage forms: cream, ointment, lotion and foam all with a strength of 0.1% (w/w) (expressed as betamethasone base) (Franz et al., 1999). A number of antibacterial/steroid topical combinations are commercially available. Betamethasone-17-valerate is often combined with antibacterials, such as neomycin sulfate (NS) (Fig 1b). This combined drugs mainly used as topical anti infection, in intestinal inflammation and infected eczema with secondary infection.
The treatment failure of combination between BV and NS was predicted, caused by drug-drug physical interaction. The easiest method to observe drug-drug physical interaction is thermal contact method by hot stage microscope (HSM). This method requires drugs should be stable before, during and after its melting point. BV does not degraded, but NS degraded before its melting point. In this case, thermal contact method cannot be used. But, some methods are available for identifying of solid state drug, such as DSC, PXRD, FTIR, SEM, solubility- and dissolution-test. Those methods are also expected to be used to identify the changes the solid state drug due to drug-drug physical interaction.
The aim of this research was to determine the type of physical or intermolecular interaction between BV-NS and physical properties changed of either BV or NS.
METHODOLOGY Material
Betamethasone-17-valerate (BV) and neomycin sulfate (NS) commercial material with purity of
>99% were purchased from PT. Kimia Farma, tbk, Indonesia. Methanol, ethanol, and other reagents were obtained from E-Merck without any purification.
Methods
Binary phase of diagram
The samples containing physical mixture of BV and NS in different weight ratio (10:0, 9:1, 7:3, 1:1, 3:7, 1:9, and 0:10) were prepared and measured by Perkin-Elmer DSC-6 differential scanning calorimeter. Endothermic peak (melting events) of interaction was plotted against the weight ratio of the mixture.
Contact method of solution
A drop of BV solution in methanol was placed on object glass and covered, then allowed to recrystallize. One droplet of NS solution in methanol was placed at the other side of cover glass. NS solution left in contact with the crystal BV. Optical microphotographs of crystal were taken under polarizing microscope (Olympus BX-51). The microscopic images were recorded with a Olympus SC-30 digital color camera attached to the Olympus BX-51 microscope.
Fikri Alatas
Preparation of BV-NS(1:1) by solution crystallization
A 1:1 mol fraction mixture of BV (95.31 mg, 0.2 mmol) and NS (142.54 mg, 0.2 mmol) was added to 20 ml of ethanol 70% in a 25 ml conical flask and gently heated. The solution was allowed to evaporate slowly at the ambient conditions. The predicted BV–NS crystals were then scaled up to 2 g for further analysis.
Preparation of BV-NS (1:1) by solvent drop grinding experiments
A 1:1 mol fraction mixture of BV (95,3 mg, 0.2 mmol) and NS (142,5 mg, 0.2 mmol) were placed in a mortar and five drop of methanol was added. The mixture was grinded for 15 and 30 min in Retsch RM 100 mortar grinder using a fresh batch for each grinding period.
Powder X-ray diffraction (PXRD)
PXRD data were collected with Shimadzu XRD-7000 X-ray powder diffractometer. The sample was scanned within the scan range of 2θ = 5° to 35° continuous scan, at a scan rate of 2°/min.
Thermal Analysis by DSC
Differential scanning calorimetry (DSC) was performed with a Perkin Elmer DSC-6. 2-5 mg of each crystal sample was placed in crimped sample pan. The sample was heated from 30 to 350°C at a heating rate of 10°C/min. The samples were purged with a stream of flowing nitrogen at 20 mL/min.
Fourier Transform Infra Red (FTIR)
The FTIR spectra of each sample were recorded on Perkin-Elmer FTIR.
Scanning Electron Microscopy
The electron microscopy measurements were performed at a Carl Zeiss scanning electron microscope (SEM).
Determination of BV solubility
The solubility of BV in water were determined at room temperature using a orbital shaker on each sample. Excess amounts of compound were added to 5 mL of the media, mix it continuously and then filtered after 48 h of equilibration. The bulk solutions were measured spectrophotometrically using Shimadzu 1601-PC spectrophotometer at 242 nm. The calibration curve for BV (y=0.0327+0.003 was linear from 1.31 to 20.00 µg/ml (r=0.9999). The experiments were carried out in triplicate.
In vitro dissolution of BV
Dissolution test of BV were carried out in water (900 ml, 37±0.5°C, 100 rpm) for 90 min using the USP XXIII paddle apparatus (ZRS-6G, Tianjin, China). At predetermined time intervals, 5 ml samples were withdrawn and spectrophotometrically assayed (Shimadzu 1601-PC spectrophotometer) for drug concentration at 242 nm.
RESULTS AND DISCUSSION
Thermoanalysis offers significant advantages in saving both time and the number of substance as well. In principle, makes it possible to detect compatibility/incompatibility directly on physical mixture, avoiding the time consuming step of the annealing of the mixtures under stress conditions (Brown et al, 1999; Jacobson and Reier, 1969). Based on the melting points of BV–NS physical mixture containing various weight ratios of the components, phase diagram have been constructed (Fig. 2).
The melting point of pure BV was 192.6°C, while NS was 221.4°C followed by decomposition. DSC- curve showed two endothermic events for each composition. The melting poin of BV fixed in each weight ratio. Binary phase of diagram shows no interaction between both substances
Fig. 3 present optical microscope photos of crystals with larger size and long needle shape of BV (3A) and amorphous state of NS (3B). Fig. 3C shows photo after contact between BV crystal and NS solution. NS is always in amorphous state, diffuse form and always been cover center of several BV crystals. There was no a new habit formed. This photo indicates an interaction-like between BV and NS.
The X-ray diffraction patterns of pure BV, NS, and the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding are offset in fig 4. The PXRD-spectra patterns exhibit hallow form of the pure NS (amorphous solid). All mixtures shows the two highest intensities of characteristic interferences of BV, i.e. at 14.1° and 17.1° 2θ. The mixture of B:V (1:1) that prepared by solvent drop grinding for 30 min has the lowest relative intensity for both characteristic interferences of BV.
Interaction Between Betamethasone-17-Valerate...
Fig. 2. Binary phase diagram of physical mixture of BV and NS
(A) (B) (C)
Fig. 3. Polarized microscope photos of BV (A), NS (B), and result of contact method solution between BV and NS (C) recrystalized in methanol with magnification 200x.
Fig. 4. PXRD-spectra intensity (arbitrary units) as a function of 2θ of BV (A), NS (B), (B:V=1:1) after solution crystallization (C), (B:V=1:1) after solvent drop grinding for 15 min (D), and 30 min (E)
DSC-curve of pure BV, NS, and the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding are shown in fig 5. A broad endotherm peak at around 100 °C after crystallization and grinding process, indicates of water losses. That condition due to the extremely hygroscopic properties of pure NS, after crystallized from solution and grinded. The longer time of grinding, the larger the endothermic peak area around 100oC. The melting point of BV at 192.6°C decreases in the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding. This is aggrement with relative intensity obtained with XRD. Thus, preparation of mixture B:V (1:1) by solution crystallization and solvent drop grinding changed physical state of either components.
Fikri Alatas
Fig. 5 DSC-thermogram of BV (A), NS (B), (B:V=1:1) after solution crystallization (C), (B:V=1:1) after solvent drop grinding for 15 min (D), and 30 min (E)
(A) (B) (C)
(D) (E)
Fig. 6 Scanning electron micrographs of BV (A), NS (B), (B:V=1:1) after solution crystallization (C), (B:V=1:1) after solvent drop grinding for 15 min (D), and 30 min (E)
Interaction Between Betamethasone-17-Valerate...
Fig. 7 FTIR spectra of BV (A), NS (B), (B:V=1:1) after solution crystallization (C), (B:V=1:1) after solvent drop grinding for 15 min (D), and 30 min (E)
Fig. 8 Profile dissolution of pure BV(-♦-), physical mixture of BV:NS (1:1) (-■-), (B:V=1:1) after solution crystallization (-▲-), (B:V=1:1) after solvent drop grinding for 15 min (-x-), and 30 min (-●-)
Fig. 6 shows representative SEM pictures of some of the samples.The morphology of the particles showed prismatic shape of BV and irregular shape of NS. In the mixture of B:V (1:1) that prepared solvent drop grinding for 15 and 30 min, the habit of BV crystals become irregular and smaller.
Fig. 7 shows FTIR-spektra of of pure BV, NS, the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding. There was no new peak seen in spektra of the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding.
Solubility experiments showed that solubility of BV in water increased in the mixture of B:V (1:1) that prepared solvent drop grinding. There was significant increasing of solubility of BV in the mixture of B:V (1:1) that prepared solvent drop grinding. The existence of particles of NS around the BV crystals causes BV easily wetted, so that its solubility increases. This is aggrement with XRD results. This result indicate an interaction between BV and NS.
Fikri Alatas
Tabel 1. Solubility of betamethasone-17-valerate
Material Solubility (µg/mL)
Betamethasone-17-valerate 13.11±0.33
B:N (1:1) solution crystallization 10.78±0.47 B:N (1:1) solvent drop grinding for 15 minutes 29.94±0.97 B:N (1:1) solvent drop grinding for 30 minutes 56.77±1.11 n=3
The profile dissolution of pure BV and the mixture and the mixture of B:V (1:1) that prepared by solution crystallization and solvent drop grinding are showed in fig 9. The dissolution percentage of BV from the mixture of B:V (1:1) that prepared solvent drop grinding increased. There was no significant difference in dissolution profile between pure BV, physical mixture of B:V (1:1) and that prepared by solution crystallization. The dissolution percentage at 90 min (DP90 min) of the mixture of B:V (1:1) that prepared by solvent drop grinding for 30 min was 43.50% higher than others.
CONCLUSION
The mixture of BV:NS (1:1) that prepared by solvent drop grinding showed an interaction between BV and NS. Solubility and dissolution rate of BV increased from BV-NS (1:1) that prepared by solvent drop grinding. The changes of solid state characteristics of BV and NS in the mixture that investigated by contact method of solutions, DSC, PXRD, SEM, solubility- and dissolution-test indicate an interaction between the BV-NS.
REFERENCES
Del Rosso, J., Friedlander, S.H., 2000. Corticosteroids: options in the era of steroid-sparing therapy. J.
Am. Acad. Dermatol. 53, 50–58.
Sivaramakrishnan, R., Nakamura, C., Mehnert, W., Korting, H.C., Kramer, K.D., Schafer-Korting, M., 2004.
Glucocorticoid entrapment into lipid carriers-characterisation by paralectric spectroscopy and influence on dermal uptake. J. Control. Release 97, 493–502.
Wiedersberg, S., Leopold, C.S., Guy, R.H., 2008. Bioavailability and bioequivalence of topical glucocorticoids. Eur. J. Pharm. Biopharm. 68, 453–466.
Franz, T.J., Parsell, D.A., Halualani, R.M., Hannigan, J.F., Kalbach, J.P., Harkonen, W.S., 1999.
Betamethasone valerate foam 0.12%:a novel vehicle with enhanced delivery and efficacy. Int. J.
Dermatol. 38, 628–632.
Bettinetti, G. Caira, M. R., Callegari, A. Merli, M., Sorrenti, M., Tadini, C., 2000. Structure and solid-state chemistry of anhydrous and hydrated crystal forms of the trimethoprim sulfamethoxypyridazine1:1 molecular complex, Journal of Pharmaceutical Sciences, 89(4), 478–
489.
Li Wan Po, Mroso P.V., 1984. Drug-drug incompatibility in the solid state: kinetic interpretation, modelling and prediction, Int. J.Pharm. Sci., 18(3), 287-298.
H. Jacobson and G. Reier, 1969. Application of differential thermal analysis to compatibility and stability problems in penicillin-stearic acid mixtures, J. Pharm. Sci., 58 (5) 631-633
M. E. Brown, E. M. Antunes, B. D. Glass, M. Lebete and R. B. Walker, 1999. DSC Screening of Potential Prochlorperazine-Excipient Interactions in Preformulation Studies J. Therm. Anal. Cal., 56 (3) 1317-1322
Sundani, N.S., Moegihardjo, Jessie S.P., Rachmat, M., 2008. Intermolecular Interaction between Ibuprofen and Acetaminophen, Asian Scientific Conference in Pharmaceutical Technology, Penang, Malaysia.
Interaction Between Betamethasone-17-Valerate...
Sundani, Fikri A., Ilma N., 2007. Identification of Interaction between Benserazide and Levodopa, The International Conference on Neutron and X-ray Scattering, Bandung, Indonesia.