Introduction
The drug ketotifen is a benzocycloheptathiophene derivative which has been reported to have anti- histaminic and anti-anaphylactic properties [1]. Ketotifen antagonizes histamine at H1 receptors at mast cells, inhibits calcium uptake, blocks passive cutaneous anaphylactic reaction, reverses isoprenaline induced beta-adrenoceptor tachyphylaxis, and inhibits both allergen-induced and drug-induced asthma [2]. Through a number of clinical trials, this drug has been shown to have a beneficial effect in the treatment of asthma [3-4]. Domperidone is an antidopaminergic drug used to suppress nausea and vomiting, as a prokinetic agent and for promoting lactation. It is a specific blocker of dopamine receptors. It speeds gastrointestinal peristalsis, causes prolactin release, and is used as antiemetic and tool in the study of dopaminergic mechanisms. There is some evidence that domperidone has antiemetic activity [5]. Domperidone is used, along with metoclopramide, cyclizine, and 5HT3 receptor antagonists to treat nausea and vomiting. Domperidone can be used in patients with Parkinson's disease [6] because, unlike metoclopramide [7], domperidone does not cross the blood–brain barrier. Domperidone has also been found effective in the treatment of gastroparesis [8], and for paediatric gastroesophageal reflux. The major goal of the present study was to find out whether two drugs-ketotifen and domperidone might undergo drug-drug interaction at simulated gastric fluid having various pH. The absorbance of drugs at those solutions was taken and analyzed using Job’s plot [9].
Material and methods
Materials
All the chemicals and reagents used in this study were of analytical grade and were stored under optimum storage conditions. The experimental mixtures and solutions were prepared in standard volumetric flasks about one hour prior to recording the data.
Drugs used in the study: Ketotifen fumarate and Domperidone.
The lmax value of drug used in the study: 300nm (The lmax Ketotifen fumarate).
Instrument used: pH Meter, UV/VIS Spectrophotometer, Electronic balance, Water bath.
Solvents: i) Distilled water, ii) Hydrochloric acid, iii) Ethanol.
Preparation of Hydrochloric acid
In order to prepare Hydrochloride acid of 0.1 M concentration, 9.1 ml of hydrochloric acid (Molecular weight 36.5 gm/mol, 37% concentrated) was taken in a liter volumetric flask and the volume made up with distilled water to the mark. Similarly 18.18 ml of HCl acid was diluted in a liter volumetric flask up to the mark with distilled water to make the solution of 0.2 M concentration.
Preparation of Potassium chloride
In order to prepare Potassium chloride of 0.2 M concentration, Potassium chloride (14.9 gm), (Molecular weight 74.55 gm/mol) was dissolved in distilled water in a liter flask and the volume made up to the mark with same solvent.
Preparation of potassium dihydrogen phosphate
In order to prepare potassium dihydrogen phosphate of 0.1 M concentration, Potassium chloride (13.609 gm), (Molecular weight 136.09 gm/mol) was dissolved in distilled water in a liter flask and the volume made up to the mark with same solvent.
Preparation of Sodium hydroxide
In order to prepare of 0.1 M concentration, sodium hydroxide pellets (20 gms), (Molecular weight 40 gm/mol) were taken in a 500 ml volumetric flask, dissolved in little distilled water and volume was made up to the mark with the same solvent. 100 ml of this solution (1 M concentration) was further diluted in 500 ml volumetric flask with distilled water, resulting concentration was 0.2 M.
Preparation of acidic buffer (pH 0.4, 1.2, 2.0, and 2.8)
These buffers are prepared by using sodium chloride, potassium chloride, sodium hydroxide and hydrochloric acid with the help of pH meter.
Preparation of Basic buffer (pH 6.0, 6.8, and 7.4)
These buffers are prepared by using Potassium dihydrogen phosphate (KH2PO4), potassium chloride, sodium hydroxide and hydrochloric acid with the help of pH meter.
Preparation of Ketotifen Fumarate solution
100 ml of 1*10-3 M solution of Ketotifen Fumarate was prepared as the stock solution by dissolving 0.425 gm of Ketotifen Fumarate in 100 ml of distilled water in a 100 ml Volumetric flask. To prepare 1*10-5 M solution of Ketotifen Fumarate, 1 ml of 1*10-3 M solution was taken in another 100 ml volumetric flask and the volume was adjusted by distilled water up to the mark.
Preparation of Domperidone solution
100 ml of 1*10-4 M solution of Domperidone was prepared as the stock solution by dissolving 0.425 gm of Domperidone in 100ml of distilled water in a 100 ml Volumetric flask. To prepare 1*10-5 M solution of Domperidone, 1ml of 1*10-4 M solution was taken in another 10 ml volumetric flask and the volume was adjusted by distilled water up to the mark.
Methods
Job plot ,also known as the method of continuous variation or Job's method was used to analyze the free drug concentration after concurrent administration using the observed spectroscopic data. According to Job's method (Job, 1971) a series of solutions were prepared in which the analytical concentration of one reactant (usually the cation) was held constant while that of the other was varied. The absorbance of a series of Ketotifen Fumarate with domperidone in different molar ratios (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1) was measured by keeping the total molar concentration constant. The observed absorbance of the mixtures at various molar fractions was subtracted from the sum of the values for the free drugs (Ketotifen Fumarate and domperidone). The absorbance difference (D) was then plotted against the molar fractions of the drug in the mixtures. If the formation constant is reasonably favourable, two straight lines with different slopes that intersect at a molar ratio that corresponds to the ratio of drugs in the complex are obtained.
Results
In the present investigation, the interaction of Ketotifen Fumarate and Domperidone has been studied by different methods of analysis under different pH (0.4, 1.2, 2.0, 2.8, 6.0, 6.8 and 7.4) at different concentrations. The spectral characteristics and spectrophotometric analysis of the complexation process have been evaluated. The results obtained from various methods are discussed below.
Spectral studies of interaction of Ketotifen Fumarate & Domperidone
In spectral observation analysis, each of the drugs studied showed absorption in UV-VIS region. The molecular species of Ketotifen Fumarate & Domperidone when separately mixed showed some changes in absorption characteristics of this drug molecule including some shifts in the absorption maxima. Initial detection of complexation of Ketotifen Fumarate with Domperidone was done from the nature of spectra of pure compounds as well as their 1:1, 1:2 and 2:1 mixtures in buffer solution of pH 0.4, 1.2, 2.0, 2.8, 6.0, 6.8 and 7.4 at a fixed concentration (1*10-5 M). It is obvious that each compound has its unique molecular structure or electronic configuration which is responsible for absorption of light in the form of ultraviolet or visible form. For this reason the spectrum of any pure compound obtained from UV-spectrum will be of one kind that will be totally different from the other compound or the complex of that compound with other compounds. It is because interaction between two compounds may lead to form complex which has different light absorption capacity (due to change in physicochemical and optical properties) and the spectral pattern is altered. Thus alteration in spectral pattern may be regarded as an indicator for the primary interaction of drugs. The spectra of target molecules alone and mixture of Ketotifen Fumarate with Domperidone showed significant changes in their absorption intensities. This may be due to the interaction of Ketotifen Fumarate with Domperidone that alter the absorption intensities as complexation occurs.
Effect of Domperidone on Ketotifen Fumarate by Job’s method of continuous variation at different pH
The molar ratios of the complexes of Ketotifen Fumarate with Domperidone were estimated by Job’s spectrophotometric method of continuous variation. The observed absorbance values measured in pH 0.4, 1.2, 2.0, 2.8, 6.0, 6.8 and 7.4 at various concentrations 1*10-5 M to 9*10-5 M Ketotifen Fumarate with Domperidone at 300nm is given in Tables 1-7. In this method, solutions of different concentrations of Ketotifen fumarate and Domperidone were prepared by plotting corrected absorbance against the volume fraction of one reactant. It may be mentioned that drug solutions with identical analytical concentrations are mixed in such a way that total volume and the total moles of reactant in each mixture is constant but the mole ratio of the reactants varies systematically. At pH 0.4, 1.2, 2.0, 2.8, 6.0, 6.8 and 7.4 Ketotifen Fumarate forms strong 1:1 complex with Domperidone.
Table 1. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 0.4
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. difference |
|
M × 10-5 |
A |
M×10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.160 |
9 |
1.028 |
0.297 |
0.891 |
|
2 |
0.268 |
8 |
0.918 |
0.302 |
0.884 |
|
3 |
0.419 |
7 |
0.8 |
0.317 |
0.902 |
|
4 |
0.543 |
6 |
0.689 |
0.347 |
0.885 |
|
5 |
0.687 |
5 |
0.575 |
0.424 |
0.838 |
|
6 |
0.826 |
4 |
0.441 |
0.538 |
0.729 |
|
7 |
0.971 |
3 |
0.334 |
0.679 |
0.626 |
|
8 |
1.129 |
2 |
0.193 |
0.910 |
0.466 |
|
9 |
1.229 |
1 |
0.116 |
1.015 |
0.330 |
Table 2. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 1.2
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. difference |
|
M × 10-5 |
A |
M × 10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.14 |
9 |
0.927 |
0.230 |
0.837 |
|
2 |
0.300 |
8 |
0.817 |
0.239 |
0.878 |
|
3 |
0.403 |
7 |
0.711 |
0.258 |
0.856 |
|
4 |
0.556 |
6 |
0.603 |
0.308 |
0.851 |
|
5 |
0.670 |
5 |
0.501 |
0.395 |
0.776 |
|
6 |
0.820 |
4 |
0.386 |
0.524 |
0.682 |
|
7 |
0.970 |
3 |
0.277 |
0.679 |
0.568 |
|
8 |
1.093 |
2 |
0.192 |
0.860 |
0.376 |
|
9 |
1.234 |
1 |
0.143 |
1.256 |
0.121 |
Table 3. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 2.0
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. Difference |
|
M × 10-5 |
A |
M × 10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.167 |
9 |
1.071 |
0.270 |
0.968 |
|
2 |
0.318 |
8 |
0.935 |
0.280 |
0.973 |
|
3 |
0.446 |
7 |
0.813 |
0.307 |
0.952 |
|
4 |
0.608 |
6 |
0.696 |
0.353 |
0.951 |
|
5 |
0.773 |
5 |
0.56 |
0.463 |
0.870 |
|
6 |
0.915 |
4 |
0.464 |
0.588 |
0.791 |
|
7 |
1.059 |
3 |
0.324 |
0.742 |
0.641 |
|
8 |
1.118 |
2 |
0.221 |
0.967 |
0.362 |
|
9 |
1.349 |
1 |
0.112 |
1.261 |
0.200 |
Table 4. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 2.8
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. difference |
|
M × 10-5 |
A |
M × 10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.137 |
9 |
1.019 |
0.264 |
0.892 |
|
2 |
0.275 |
8 |
0.901 |
0.268 |
0.908 |
|
3 |
0.426 |
7 |
0.768 |
0.286 |
0.908 |
|
4 |
0.588 |
6 |
0.651 |
0.321 |
0.918 |
|
5 |
0.722 |
5 |
0.54 |
0.408 |
0.854 |
|
6 |
0.868 |
4 |
0.433 |
0.557 |
0.744 |
|
7 |
0.993 |
3 |
0.303 |
0.696 |
0.600 |
|
8 |
1.126 |
2 |
0.193 |
0.923 |
0.396 |
|
9 |
1.271 |
1 |
0.103 |
1.104 |
0.270 |
Table 5. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 6.0
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. difference |
|
M × 10-5 |
A |
M × 10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.161 |
9 |
0.350 |
0.100 |
0.411 |
|
2 |
0.340 |
8 |
0.317 |
0.132 |
0.525 |
|
3 |
0.471 |
7 |
0.285 |
0.201 |
0.555 |
|
4 |
0.623 |
6 |
0.225 |
0.260 |
0.588 |
|
5 |
0.702 |
5 |
0.220 |
0.372 |
0.55 |
|
6 |
0.880 |
4 |
0.172 |
0.532 |
0.52 |
|
7 |
0.973 |
3 |
0.111 |
0.620 |
0.464 |
|
8 |
1.271 |
2 |
0.082 |
0.921 |
0.432 |
|
9 |
1.190 |
1 |
0.040 |
1.031 |
0.199 |
Table 6. Values of job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 6.8
|
Conc. of Ketotifen |
Absorb. of Ketotifen |
Conc. of Domperidone |
Absorb. of Domperidone |
Absorb. of mixture |
Absorb. difference |
|
M × 10-5 |
A |
M × 10-5 |
B |
C |
D=(A+B)-C |
|
1 |
0.123 |
9 |
0.947 |
0.206 |
0.864 |
|
2 |
0.259 |
8 |
0.841 |
0.234 |
0.866 |
|
3 |
0.420 |
7 |
0.657 |
0.242 |
0.835 |
|
4 |
0.528 |
6 |
0.550 |
0.292 |
0.786 |
|
5 |
0.676 |
5 |
0.452 |
0.388 |
0.74 |
|
6 |
0.811 |
4 |
0.362 |
0.513 |
0.66 |
|
7 |
0.931 |
3 |
0.274 |
0.660 |
0.545 |
|
8 |
1.076 |
2 |
0.175 |
0.858 |
0.393 |
|
9 |
1.174 |
1 |
0.102 |
1.020 |
0.256 |
Figure 1. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 0.4
Figure 2. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 1.2
Figure 3. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 2.0
Figure 4. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 2.8
Figure 5. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 6.0
Figure 6. Job’s plot for complexation of Ketotifen Fumarate with Domperidone at pH 6.8
Discussion
Previous works on human subjects as well as animal models suggest that Domperidone goes into a number of drug-drug interactions [10-12]. As Ketotifen Fumerarate and Domperidone are often prescribed together, this study investigates the possible interaction between these two drugs through in vitro study. The two drugs under investigation were interacted together at different pH. Different concentrations comprising 1*10-5 M to 9*10-5 M of ketotifen were interacted with domperidone. The breakdowns in the curves of ketotifen were found at 5*10-5, 4*10-5, 4*10-5, 4*10-5, 6*10-5 and 3*10-5 at the pH of 0.4, 1.2, 2.0, 2.8, 6.8 and 7.4 respectively. However, no break in the curve at pH 6 was observed. So it was assumed that there was no interaction at pH 6.
Conclusion
The experimental results indicate that interaction of ketotifen with domperidone decreases the free drug concentration of both drugs which may result in decreased affinity towards the receptors. Consequently one or both drugs may show diminished pharmacological activity in the system. However, further study using animal model is required to estimate the bioavailability of these drugs when administered into the system.
Acknowledgement
This study would not have been possible unless we couldn’t get help from Department of Pharmacy, International Islamic University Chittagong. This department provided us with all equipments and materials to complete this task. We are obliged to our friend Jannatul Ferdous Mithu who supported and encouraged us throughout the process.
Conflict of interest
No conflict of interest has been declared by the authors.
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© 2013, Sayeed M.S., Farhad F.M., Tareq S.M., Ikram M., Islam M.N., Siddique S.A., Das D.
© 2014, Russian Open Medical Journal
Received 9 December 2013, Revised 15 April 2014, Accepted 10 June 2014
Correspondence to Fuad Mohammed Farhad. Address: Department of Pharmacy, International Islamic University Chittagong, Bangladesh. Tel: +88 01920555598. E‐mail: fuadekushe_52@yahoo.com
