Eraga et al., Nig. Journ. Pharm. Sci., September, 2017, Vol. 16 No.2, P78-85

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2

ANALYSIS OF THE PHARMACEUTICAL QUALITY OF COMMERCIALLY

AVAILABLE PARACETAMOL 500 MG TABLETS IN BENIN CITY METROPOLIS

USING RP-HPLC

*1Eraga, S.O., 2Odili, V. U., 1Meko, O. A., 1Igumah, G. O. and 1Iwuagwu, M. A

1Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmacy,

University of Benin, Benin City, 300001, Nigeria.

2Department of Clinical Pharmacy and Pharmacy Practice, Faculty of Pharmacy, University of

Benin, Benin City, 300001, Nigeria.

*Author for correspondence: eragaso@uniben.edu, Tel: +2348030884928

ABSTRACT

Paracetamol tablets are the most prescribed analgesics and antipyretic agents. This has resulted in increased

manufacturing of various brands of the tablets in Nigeria. There is the need to routinely assess the

pharmaceutical quality of the available brands of the tablets to reduce the manufacture of counterfeit,

substandard or adulterated products. The study investigated the pharmaceutical quality and the presence of 4-

aminophenol (a degradative product of paracetamol) in available brands of paracetamol tablets from pharmacies

in Benin City, Nigeria. The purchased drug samples were evaluated for their uniformity of weight, crushing

strength, friability, disintegration and dissolution tests following official pharmacopoeial protocols. The

paracetamol content and the presence of 4-aminophenol in the tablets were determined using Reverse Phase

High Performance Liquid Chromatographic (RP-HPLC) method. The tablets were uniform in weight with

crushing strength values ranging from 8.6 - 12.5 kp while the disintegration times were within 15 min except a

brand with a disintegration time of 1.5 h. Friability values were less than 1.0% and the amount of paracetamol

released within 30 min ranged between 65 - 100% with a brand failing the test. All the brands met compendial

specifications with their content of active and recorded no presence of 4-aminophenol in their tablet dosage

forms. Ten out of eleven brands of paracetamol 500 mg tablets assessed met all acceptable standards. Therefore,

there is the need to routinely and continuously carry out sentinel market surveillance of pharmaceutical drug

products.

Keywords: RP-HPLC, assay, paracetamol, pharmaceutical quality, label claim

1.0 INTRODUCTION

Paracetamol also known as acetaminophen (N-acetyl-p-aminophenol) is a widely used antipyretic and analgesic accepted as an effective treatment for the relief of pain and fever in patients including children, pregnant women and the elderly (Bloomfield, 2002;

Bertolini et al., 2006; Karmakar and Kibria, 2012; Zaid et al., 2013). It is available in different formulations such as solutions, elixirs, syrups, tablets, capsules, injections, etc., that are used worldwide due to their high efficacy and tolerance, lower adverse effects and toxicity (Penna and Buchanan, 1991). Paracetamol is also very cheap and

Nigerian Journal of Pharmaceutical Sciences Vol. 16, No.2, 2017, ISSN: 0189-823X All Rights Reserved

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readily available as an over-the-counter preparation. Therefore, it ranks as one of the most commonly used analgesic medications in Nigeria (Oladimeji and Iranloye, 1990).

Reports have been made from various regions across the country on the variations on the physicochemical and pharmaceutical equivalence of the various brands of paracetamol tablets available in the Nigerian market (Oga et al., 2010; Sani et al., 2012; Awemu et al., 2015). Daily, healthcare providers are confronted with the problem of generic substitution (Auta et al., 2014), influenced by factors such as cost, efficacy, aesthetic packaging and recently the assignment of NAFDAC number on packaging. The National Agency of Food and Drug Control and Administration (NAFDAC) is the agency for the regulation, control and administration of the quality of food and drugs in Nigeria. Thus, the community pharmacist faces the problem of making the right choice of selecting the most effective brand to dispense to the patient. It is therefore necessary to routinely assess the pharmaceutical quality of these drugs in Nigerian market (Nnamdi et al., 2009).

4-aminophenol (4AP) is the primary degradation product of paracetamol which is limited at a low level (50 ppm or 0.005% w/w) in the pure drug substance by Pharmacopoeias but for drug products, often higher specification limits, such as 1000 ppm are applied (Bloomfield, 2002; Wyszecka-Kaszuba et al., 2001; Dejaegher et al., 2008). It is formed during the synthesis of paracetamol or during storage of the pure drug or drug products. Although animal studies have shown its low toxicity, it has been implicated in paracetamol induced methemoglobinemia in animals and humans (McConkey et al., 2009; Acton, 2011). This study seeks to establish the

pharmaceutical quality and to investigate the presence of 4-aminophenol in the various brands of paracetamol 500 mg tablets in Nigeria, using Benin City as a reference point.

2.0 MATERIALS AND METHODS

2.1 Materials Paracetamol powder (William Ransom, Hertfordshire, England), 4-amino phenol (JHD Chemicals, China) and eleven brands of paracetamol 500 mg tablets purchased from registered pharmacies in Benin City. All other reagents used were of analytical grade.

2.2 Methods

2.2.1 Drug sampling The drug samples (Table 1) studied were bought from registered pharmacies across Benin City. Benin City is a large metropolitan city located in the south-south geopolitical zone of Nigeria. It has a projected population of about 1.2 million inhabitants (Eraga et al., 2015). The city has about 120 registered community pharmacies with about 50% of them located within the vicinity of the government hospitals (city centre), while the remaining ones are scattered over the rest of the city (Oparah and Iwuagwu, 2001). The brands available in each pharmacy were pooled together and a selection of eleven different brands was made and used for the study.

2.2.2 Weight uniformity Twenty tablets were randomly selected from each brand and weighed individually using the electronic weighing balance (College B154, Mettler Toledo, Switzerland). The mean weight was calculated as well as the standard deviation.

2.2.3 Crushing strength The crushing strength was determined by diametric compression of each of ten tablets

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per sample using a motorized hardness tester (Campbell Electronics, Model HT-30/50, India). The mean value and the standard deviation were calculated.

2.2.4 Friability The weight of ten tablets per sample was determined on the electronic balance. The tablets were then placed in the drum of a friabilator (Erweka GmbH, Germany) revolving at 25 rpm. After 4 min, the tablets were removed from the friabilitor, dusted and reweighed. The weight loss was obtained from the differences between the initial weight and final weight. The friability was calculated as the percentage weight loss.

2.2.5 Disintegration time The disintegration times of six tablets per brand were determined in distilled water at 37 ± 0.5 °C using the BP disintegration tester (MK IV, Manesty Machines, UK). The average time taken for all 6 tablets to break up into granules was noted as the disintegration time and their standard deviations were calculated.

2.2.6 Content of active

2.2.6.1 Chromatographic conditions Chromatographic separation was performed on an Agilent 1260 Infinity Series (Agilent Technologies Inc., USA) arranged with a gradient pump, auto injector, column oven and DAD detector. An Agilent ZORBAX Eclipse Plus C18 100 mm x 4.6 mm, 3.5 μm column was used as the stationary phase. The drug samples were separated isocratically with a mobile phase consisting of acetonitrile, methanol and water (40:30:30) at a flow rate of 0.5 ml/min. The analysis was carried out at 25 °C and the injection volume was 0.2 ml. The detector was set at 245 nm.

2.2.6.2 Preparation of standard solutions Pure paracetamol powder (100 mg) was weighed into a 100 ml volumetric flask containing about 60 ml of the mobile phase and sonicated for 20 min. The resultant solution was allowed to settle and made up to volume. Ten millilitres aliquot of the solution was diluted to 100 ml to get a concentration of 100 μg/ml. The standard solution was run on the HPLC. Six injections were run for the standard to determine the system suitability and also calibrated to obtain their retention times and relative standard deviation (RSD) (Umapathi et al., 2012). The procedures were repeated using 100 mg of pure 4-aminophenol powder.

2.2.6.3 Sample preparation Twenty randomly selected tablets from each brand were weighed and pulverized. The weight of powder equivalent to 500 mg paracetamol was transferred into a 500 ml volumetric flask. About 400 ml of the mobile phase was added and sonicated for 20 min. After dissolving, the solution was allowed to settle down and made up to volume. The solution was filtered through a 0.45 μm Sartorius nylon filter and 1.0 ml was taken and diluted to 50 ml with the mobile phase in a volumetric flask to get a test solution of 100 µg/ml. The sample was analysed using HPLC. Three injections each were run on each brand and their peaks area and retention times recorded. The mobile phase was also run to serve as the blank (Umapathi et al., 2012). The peaks area of the brands were quantified with the area of the peak of the paracetamol standard to get the amount of the paracetamol in percentage present in each brand. Agilent Chemstation software was used to integrate and analyze the peak responses for quantitation by area percent. The peaks retention times were also compared with those of the paracetamol standard and 4-aminophenol standard to detect any presence of 4-aminophenol.

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2.2.7 Dissolution test Dissolution studies were carried out on the tablets using the BP Dissolution apparatus II (paddle method) (Caleva ST7, UK). A dissolution medium of 900 ml of 0.1 M HCl solution maintained at 37 ± 1 ºC with a paddle revolution of 50 rpm was used. Three tablets per brand was randomly selected and used in the determination. A 5 ml quantity of the dissolution medium was periodically withdrawn and replaced with an equal amount of fresh dissolution medium at 5, 10, 15, 20, 30, 45 and 60 min. Each of the samples withdrawn was filtered with a fresh filter paper and the filtrate diluted appropriately. The absorbance values of the diluted filtrate were read spectrophotometrically at max of 245 nm with 0.1 M HCl solution as blank (CE 7500, Cecil Instruments Ltd). The concentration and the percentage of drug released at each time interval was determined using the equation from the standard calibration plot obtained from the pure paracetamol. A minimum of triplicate determinations were carried out for each brand and the results were reported as mean ± SD.

3.0 RESULTS

All the brands of paracetamol tablets studied (Table 1) were manufactured in Nigeria and registered with the National Agency for Food and Drug Administration and Control (NAFDAC). They were all within their shelf lives and were uncoated and immediate release dosage forms with label strength of 500 mg. Except samples E and F whose tablets shape were oblong, all others were round in shape.

Table 1: Brands of Paracetamol Tablets used in the Study

Code Country

of Origin

Expiry Date

Batch/ Lot No.

NAFDAC No.

Brand Name

A Nigeria Oct

2019 16327 04-0495 Bonadol

B Nigeria Jan

2022 AI70165 A170165 M&B

C Nigeria Jan

2022 402W 04-0411 Emzor

D Nigeria Nov 2019

P17 04-1853 Tumol-

500

E Nigeria Sept 2020

MI02801 B4-1774 Yef

F Nigeria Apr 2021

19970 04-0261 Emcap

G Nigeria Oct

2020 2195 04-6859 Divamol

H Nigeria Oct

2019 I60275 B4-1593 Paratex

I Nigeria Nov 2019

TZ 15 O4-4708 Zamba

J Nigeria Dec 2021

F6117 04-1217 Painkill

K Nigeria Mar 2020

021Y 04-0205 Panadol

Table 2 shows some tablet parameters of the various brands of paracetamol tablets. The weight uniformity test on the tablets indicated no significant variations in the weights of tablets within the different brands but there were significant weight variations among the brands. Hence all the brands conformed to the British Pharmacopoeia specification, which recommends that not more than two of the individual tablet weights should deviate from the average weight by more than ± 5% and none should deviate by more than ± 10% (BP, 2009).

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Table 2: Some Tablets Properties of the Paracetamol Tablets Studied

Brand Code

Weight (mg)

Crushing strength (kp)

Friability (%)

Disintegration time (min)

Drug released at 30 min (%)

A 570.12 ± 0.03 9.60 ± 1.25 0.25 ± 0.12 5.60 ± 0.73 87.27 ± 0.30 B 559.20 ± 0.02 10.50 ± 1.54 0.22 ± 0.02 0.65 ± 0.31 100.0 ± 0.10 C 572.23 ± 0.04 10.0 ± 1.35 0.20 ± 0.12 0.71 ± 0.35 100.0 ± 0.20 D 574.13 ± 0.05 10.0 ± 1.35 0.13 ± 0.06 13.87 ± 0.91 82.94 ± 0.50 E 550.02 ± 0.01 8.60 ± 0.87 0.22 ± 0.42 1.80 ± 0.67 92.02 ± 0.60 F 557.21 ± 0.02 10.10 ± 1.43 0.24 ± 0.56 1.05 ± 0.54 100.0 ± 0.32 G 550.08 ± 0.02 9.10 ± 1.07 0.32 ± 0.62 1.13 ± 0.66 95.45 ± 0.40 H 570.06 ± 0.03 9.30 ± 1.19 0.35 ± 0.40 0.55 ± 0.30 100.0 ± 0.52 I 564.04 ± 0.03 12.50 ± 1.84 0.12 ± 0.32 90.80 ± 1.31 65.92 ± 0.20 J 568.32 ± 0.04 8.87 ± 0.98 0.30 ± 0.12 1.06 ± 0.52 92.60 ± 0.45 K 570.07 ± 0.02 10.30 ± 0.19 0.15 ± 0.40 0.45 ± 0.20 100.0 ± 0.20

Table 2 also shows that the mean tablet crushing strength for the samples ranged from 8.6 - 12.5 kp while their friability values were below 1.0%. The disintegration times of the samples met the BP 2009 requirements of within 15 min for uncoated tablets (BP, 2009) except tablets of brand I with a disintegration time of 90.80 min (1.5 h). The in-vitro drug release data (Table 2) shows that all the samples except tablets of brand I, released over 80% of their labeled contents within 30 min, complying with the BP specification (BP, 2009). The dissolution profiles (Figures 1a and 1b) shows that all

the brands studied except brand I tablets achieved almost a 100% paracetamol release within 60 min. Brand I tablets achieved a maximum release of 72% within the 60 min of testing. The results from the assay of the paracetamol tablets for their chemical content and presence of 4-aminophenol are presented in Table 3. The British Pharmacopeia, 2009 and the United States Pharmacopeia, 2011 stipulate a 90 - 110 % of active drug content. All the brands met this requirement in the HPLC assay and none of the brands recorded any presence of 4-aminophenol in the assay.

Figure 1a: Dissolution profiles of drug samples A-F

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Figure 1b: Dissolution profiles of drug samples G-K

Table 3: Assay Result obtained from HPLC Analysis of the Paracetamol Tablets

Brand Code

Amount (mg/tablet) Percentage Label Claim

Presence of 4-aminophenol Labeled Amount Found

A 500 480 96 - B 500 520 104 - C 500 495 99 - D 500 510 102 - E 500 470 94 - F 500 480 96 - G 500 490 98 - H 500 480 96 - I 500 470 94 - J 500 505 101 - K 500 510 102 -

4.0 DISCUSSION

The pharmaceutical quality of eleven brands of paracetamol 500 mg tablets from various registered pharmacies across Benin City metropolis has been evaluated. All the brands met compendial requirements with regards to uniformity of weight, crushing strength and friability. The uniformity of weight within exhibited by each brand

studied can be used as an indirect or direct measure of the amount of drug substance in the tablet (Alderborn, 2013). The United States Pharmacopeia also views a direct implication of tablet’s weight variation on the uniformity of dosage unit or content uniformity (USP, 2011). Even though, there was compliance within each brand, the differences in tablet weight could be

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accounted for by the manufacturer’s choice of amounts of the other tablets excipients.

The crushing strengths shown by the tablet will ensure resistance to damage during handling, packaging and transportation. Though all the brands studied exceeded the BP 2009 optimal crushing strength recommendation of 5 - 8 kp, these values are acceptable as long as the tablet hardness does not significantly increase the disintegration times of the tablet and in turn significantly affect dissolution of the drug. The low friability values for all the tablet brands is an indication of the ability of the tablet to withstand stress due to abrasive forces, without crumbling during transportation, packaging, handling and dispensing. These low values are also a reflection of the crushing strengths and the hardness of the tablets.

The disintegration time of a tablet is the rate determining step in drug dissolution and consequently the drug absorption. The type and amount of excipients used by different manufacturers may influence disintegration and consequently the bioavailability of the drug. The disintegration times of the different brands could be predicted from their tablet crushing strength values as brand I that failed the disintegration test had the highest crushing strength value. Even though the high crushing strength value of brand I was marginally higher than that of the other brands, this marginal difference may have contributed significantly to the very high disintegration time.

The dissolution profile of a drug is probably the best available indication of in vivo drug release characteristics of a drug. Based on BP and USP specifications, all the brands except brand I released over 80 % of their drug content within 30 min. Although a drug may comply with the official requirement of content of active, it may not be able to

release sufficient amount of the active drug in vivo leading to therapeutic failure. This may be the case with brand I tablets that did not meet the compendial specification in their dissolution profiles. The less than 80 % drug release could be due to its extended disintegration time leading to delay in the release of the drug from its primary coarse particles and thus preventing the drug from going into solution. This situation may be the result of the manufacturer’s negligence leading to a formulation error or a faulty formulation technique that would have been detected in the batch in-process quality control tests or the quality assurance tests of the finished product.

The dug content assay showed that all the brands met compendial requirements while the 4-aminophenol detection analysis also revealed no presence of the degradative product of the drug. These results implies a standard and stringent sourcing of raw pure API by the manufacturers from reliable sources and good storage conditions on the part of the manufacturers and pharmacies.

5.0 CONCLUSION

Ten out of eleven brands of paracetamol 500 mg tablets assessed met all pharmaceutically acceptable standards for tablets and of good quality. Therefore, there is the need for manufacturers and drug regulatory bodies, especially National Agency for Food and Drug Administration and Control (NAFDAC) to routinely and continuously carry out sentinel market surveillance of pharmaceutical drug products to ensure access to safe, quality, and efficacious drugs.

Acknowledgement The authors acknowledge the technical support received from the laboratory staff of the Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmacy, University of Benin, Benin City.

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