Audit of the Physico-Chemical Quality of Amoxicillin Based Drugs Marketed in Senegal ()
1. Introduction
One of the major causes of global morbidity remains infectious diseases [1] , specifically in low-resource countries where insufficient resources, inadequate infrastructure and poor access to health services impact disease outcomes [2] . Thus to allow access to medicines for all and at a bearable price, the Bamako initiative was adopted in 1987 by the African ministers of health during the 37th session of the World Health Organization (WHO) in Mali [3] . Amoxicillin is part of the beta-lactam family [4] . Effective against a broad spectrum of bacteria and of low toxicity for mammalian cells [5] , the use of beta-lactams represents 65% of the total world market for antibiotics [6] . A counterfeit medicine is a medicine that is deliberately and fraudulently provided with a label that does not indicate its identity and/or its true source. It can be a specialty or a generic product, and among counterfeit products, there are some that contain the right ingredients or bad ingredients or even no active ingredient and there are others where the active ingredient is in insufficient quantity or whose packaging has been falsified [7] .
So far, more than 920 medical products have been reported as counterfeit, belonging to all main therapeutic classes and concerning brand-name drugs as well as generic drugs. The WHO estimates that 25% of drugs used in developing countries are counterfeit or substandard and that 5% of antibiotics sold worldwide are counterfeit [8] . Among the counterfeit medicines discovered, many cases have shown harmful health effects. In extreme cases, we can observe the aggravation of the pathologies treated [9] . Quality control is, therefore, necessary to provide populations with quality amoxicillin and limit the consequences of the use of poor-quality amoxicillin. It is in this perspective that this work falls under the general objective of which was to contribute to the evaluation of the quality of generic drugs based on amoxicillin available in Senegal.
2. Materials and Methods
2.1. Framework and Duration of Study
The experimental study was carried out at the National Laboratory for the Control of Medicines located on Avenue Pasteur opposite the Aristide Le Dantec Hospital in Dakar, Senegal. The LNCM is responsible for the technical control of the quality of medicines in collaboration with the Department of Pharmacy and Medicines. The study took place from December 2015 to March 2016.
2.2. Material
We used the following materials: a Millipore Biocel ultrapure water apparatus, a Branson model 1510 ultrasonic bath, a Sartorius model LA23OS scale, a HANSON model SR8 plus dissolutest series 02040372, a GFL series water distiller 11052203J, a Varian Pro Star HPLC 35 composed of various models (auto Sampler model 410; UV detector model 335, column oven model 510, column L1, (C18) 4 mm × 25 cm and pump model 240), a Mettler Toledo 365 Ion pH meter Analyzer (03 pH-meter19) and a UV-Vis spectrophotometer model V-570 (Spectramanager software).
Reagents
Where: Monobasic potassium phosphate, Acetonitrile, HPLC methanol and Potassium hydroxide KOH. Reference substance (SRC amoxicillin trihydrate powder).
2.3. Methods
2.3.1. Sampling
Consisted of 42 generic amoxicillin collected from four main wholesalers in Dakar. These samples are divided into: 10 tablets of 1000 mg and 500 mg; 17 capsules of 500 mg and 15 drinkable suspensions of 500 mg; 250 mg and 125 mg.
2.3.2. Visual Inspection
Primary and secondary packaging, appearance, color and smell, note the manufacturer’s address.
2.3.3. Galenic Control: Dissolution Test of Amoxicillin Capsules
Is done according to the standards of USP 36 volume 2; 2013 [10] .
Procedure: 06 capsules per sample were introduced individually into each of the 900 ml of dissolution medium (water) at 37˚C ± 0.5˚C; we took a sample after 60 minutes. The aim was to determine the dosage of dissolved amoxicillin from absorbances at the maximum wavelength of 272 nm on filtered portions of test solutions suitably diluted with the dissolution medium. Compare to reference material with known concentration of Amoxicillin USP RS. Tolerances: not less than 80% of the indicated dosage, dissolves in 60 minutes.
2.3.4. Identification and Assay by HPLC
Preparation of samples and standard solution [10] .
NB: the tests are to be carried out on 3 test portions of the sample.
· Diluent: Dissolve 13.6 g of monobasic potassium in 2 liters of ultra-pure water, adjust the pH to 5 ± 0.1 with 45% KOH (M/V).
· Mobile phase: Made up of the following mixture: Thinner + acetonitrile (96/4).
· Preparation of the standard solution: Dissolve an exactly weighed quantity of amoxicillin RS in the diluent to have a concentration equal to 1.2 mg/ml. (Solution to be used within 6 hours).
· Preparation of samples:
Capsules: We look for the weight of powder corresponding to 100 mg of amoxicillin, then we add 100 mL of diluent (1 mg/mL) to pass through ultrasound then we filter.
Tablets: We therefore look for the weight of powder corresponding to 100 mg of amoxicillin, then we add 100 ml of diluent (1 mg/ml) to pass through ultrasound then we filter.
Powder for oral suspension: Dilute an exactly measured volume of amoxicillin oral suspension, freshly reconstituted according to the manufacturer’s instructions to obtain a solution containing approximately 1 mg of anhydrous amoxicillin per ml, filter and inject.
The test analytic were carried out according to the conditions set out in Table 1.
2.3.5. System Compliance Check
Two samples of the reference substance were taken, one of which is for the preparation of the standard working solution and the other for the preparation of the standard control solution.
· HPLC line: the standard working solution is injected 6 times to check the operation of the machine and the standard control solution 3 times to check the first sample [10] .
· UV-Vis spectrophotometry: 10 repeated readings of the working standard solution were taken to check the operation of the machine and 5 repeated readings of the control standard solution to check the first test sample [10] .
3. Results
3.1. Sampling
Gelules were in the majority with 40% followed by drinkable suspensions 36% and 24% for tablets (Figure 1).
3.2. Galenic Control
3.2.1. Visual Inspection
Upon visual inspection, all samples met the requirements of Good Manufacturing Practices for drugs. Table 2 summarizes the results of the visual inspection.
3.2.2. Mass Uniformity
The mass uniformity of capsules and tablets was therefore in line with the standard (Table 3 and Table 4).
![]()
Table 1. Chromatographic conditions.
![]()
Figure 1. Breakdown of samples by dosage form.
![]()
Table 2. Results of the visual inspection.
![]()
Table 3. Mass uniformity of tablets.
3.2.3. Capsule Dissolution Test
In the dissolution test all capsules in our sample were compliant with a rapid release of more than 80% in 60 min (86.8% to 108.8%). The results of capsule dissolution are shown in Table 5.
3.3. Identification and Determination of Amoxicillin by HPLC
3.3.1. Identification
The peak of standard amoxicillin was obtained at 4.84 mn (Figure 2). The peaks of the different samples emerged at the same retention time as the standard amoxicillin. The sample peaks were superimposed to the standard peak. Figure 3 represents the chromatogram of a sample.
3.3.2. Dosage
All samples conformed (90% - 120%) to specifications with recovery ranging from 91.5% to 118.7%. The results of the HPLC assay are given in Table 6.
![]()
Table 5. Results of the capsule dissolution test.
![]()
Figure 2. Chromatogram of amoxicillin standard.
![]()
Figure 3. Chromatogram of a sample based on amoxicillin.
4. Discussion
In this work, we proposed to carry out the control of the generics of amoxicillin within the framework of the follow-up of the quality. We therefore took 42 samples including 10 tablets, 15 drinkable suspensions and 17 capsules from 4 wholesale distributors in Senegal.
The primary and secondary packaging carried all the mandatory information required by good manufacturing practice. Visual analysis of the powder for odor and color criteria gave a white, crystalline powder with a characteristic amoxicillin odor. All the drugs were compliant in terms of the appearance of the capsules, the color and the smell of the powder. The study of the organoleptic characteristics revealed no apparent sign of degradation. Diop A et al. who detected by the visual inspection test the problems related to the presence of physical damage (breakage, dirt, cracks, foreign particles) and the absence of the expiry date [11] .
Visual inspection corresponds to the requirements of good manufacturing practices for medicinal products. This seems to show that all the samples in our study went through the normal supply circuit because GUEYE found in Senegal that nearly 67% (n = 34) of the antibiotics in the illicit sector showed non-compliance regarding labeling with absence of manufacturer’s address and/or batch number [12] .
The determination of the average weight and the variations in weight carried out on the capsules and tablets showed that the samples collected presented variations in weight in accordance with the standards generally accepted by the pharmacopoeias, that is to say, ±7.5% for capsules with an average weight between 300 mg and more and ±5% of tablets with a weight > 250 mg [13] .
The mass uniformity of capsules and tablets is therefore in line with the standard. Thus, our study allows us to note the absence of significant variations in weight which could lead to variations in dosage (under or overdose). These results do not agree with those of Lilian C. Koech who found 13.6% failure [14] .
Dissolution is an element that affects the bioavailability of the drug. Thus, a capsule or tablet that does not meet dissolution standards will necessarily have low bioavailability even with a good dosage. The dissolution test of all the capsules in our sample was compliant with a rapid release of more than 80% in 60 min (86.8% to 108.8%) [10] . All amoxicillin samples released the expected amount of active ingredient (PA) over time and met USP tolerance limits [15] .
The term PA refers to a substance that has therapeutic properties. It is therefore the essential component of the drug because the presence of PA is essential for obtaining a therapeutic effect. In our study, all amoxicillin samples exhibited retention time consistent with that of reference amoxicillin. The identification therefore complies with the specifications of USP 36, which recommends a difference in retention time between the samples and their standards of ≤2% [16] .
The dosage of PA guarantees the safety of the drug because the difference between a drug and a poison is the dose [17] . We cannot therefore speak of drugs when there is an underdose, even less when we are faced with an overdose. The underdosage of antibiotics is a source of resistance phenomena that jeopardize the achievements of antibiotic therapy in our developing countries.
Amoxicillin capsules, tablets and oral suspensions were assayed using high performance liquid chromatography. This assay made it possible to determine the amoxicillin content in all the samples analyzed. This assay showed that the samples have amoxicillin levels which are normal because they belong to the compliance interval which is [90% to 120%]. This result is different from that of Sherryl G. Robertson who found that 15% (28/190) did not meet pharmacopoeial requirements [18] . On the other hand, the Ecumenical Pharmaceutical Network, which found in one of the studies that 83 of the 92 samples (90.21%) were in complete compliance with the requirements of the pharmacopoeia [19] .
5. Conclusions
Since amoxicillin is one of the most widely used essential drugs in Senegal and even throughout the world, it is therefore essential to carry out the various checks before and after marketing authorization, not only to check the quality but also to also the constancy of the quality of these drugs. All samples in our study are 100% compliant with European and American Pharmacopoeia standards (90% - 120%).
This work gives a fairly clear idea of the quality of amoxicillin with 100% compliance.
We can therefore say that the use of amoxicillin in the formal sector guarantees a therapeutic result.
However, during storage of amoxicillin, degradation products or substances related to amoxicillin may appear in the product. Other studies will therefore have to be oriented in the direction of stability as well as the dosage of degradation products.
It will also be necessary to undertake studies on other commonly used antibiotics in order to guarantee our populations quality antibiotic therapy and thus limit the progression of resistant germs.