Aspirin, chemically acetylsalicylic acid (ASA), considered as one of the lives saving drug belongs to the class of NSAID, in conventional tablet form, is used to relieve pain, fever, and inflammation associated with many conditions, including the flu, the common cold, neck and back pain, dysmenorrhea, headache, tooth pain, sprains, fractures, myositis, neuralgia, synovitis, arthritis, bursitis, burns, and various injuries. It is also used for symptomatic pain relief after surgical and dental procedures. It causes gastric mucosal irritation resulting to gastric hemorrhage when it is administered as uncoated tablet. So the side effect of aspirin can be prevented by applying a thick enteric coat around the aspirin tablet.  It blocks prostaglandin synthesis. It is non- selective for COX-1 and COX-2 enzymes. Inhibition of COX-1 results in the inhibition of platelet aggregation for about 7-10 days (average platelet lifespan). The acetyl group of acetylsalicylic acid binds with a serine residue of the cyclo oxygenase-1 (COX-1) enzyme, leading to irreversible inhibition. This prevents the production of pain-causing prostaglandins. This process also stops the conversion of arachidonic acid to thromboxane A2, which is a potent inducer of platelet aggregation Label. ASA binds to serine residue on the active site of COX-2 in the same fashion as its binding to the serine residue located on the active site of COX-1. The active site of COX-2 is, however, slightly larger than the active site of COX-1, so that arachidonic acid (which later becomes prostaglandins) manages to bypass the aspirin molecule inactivating COX-2. ASA, therefore, exerts more action on the COX-1 receptor rather than on the COX-2 receptor. Pharmaceutical manufacturers are focusing on development of new drug delivery systems for existing drug with more efficacy and bioavailability. The oral route of administration is the routine and most predominant method of administering drugs for systemic effects. Absorption of drug is monitored by physicochemical properties of drugs, their formulations, and routes of administration, when drug is administered orally. So the dosage forms can have a significant effect on the quality control parameters such as weight variation, hardness, friability, wetting time, disintegration time, dissolution profile etc. Also, these parameters are essential tools for maintaining batch to batch consistency during manufacturing process. This work mainly focus on the in-vitro quality control tests of three brands of aspirin marketed tablets and compared with pharmacopeial specifications1-3.

MATERIALS AND METHODS:

Chemicals

Three brands of aspirin tablets of different manufacturers with labeled contents of 150 mg were procured from various pharmacies of Dindigul district in Tamilnadu (Table 1). All the brands were properly checked for their physical appearance, manufacturer’s name, batch number, manufacturing date, expiration date, manufacturing license number, and the maximum retail price at the time of purchase. The samples were properly coded with ASP-1, ASP-2 and ASP-3.

Equipment’s

Equipments utilized for this study were Electronic Balance (Wensar), Hardness Tester (Vinsyst), Friability Test Apparatus (Rolex India), pH meter (Infra Digi), Disintegration Test Apparatus (Rolex India), Dissolution Test Apparatus USP (Ceyone) and UV Visible Spectrophotometer (Sytronics).

Preparation of the standard curve

About 100 mg of pure drug of aspirin was accurately weighed and dissolved in ethanol, then the volume was made up to the mark with distilled water in a 100 ml standard flask. It is said to be primary stock, 1 ml of this solution was pipetted out and transferred to 100 ml standard flask and the volume was made up to the mark with distilled water, named as secondary stock solution having the concentration of 10 ?g/ml. From the secondary stock solution aliquots equivalent from 1 ml to 10 ml were pipetted out and transferred into a series of 10 ml standard flask and volume made up to the mark with distilled water. The absorbance of all the above solutions was measured against distilled water as blank at 227 nm using UV-Visible spectrophotometer. Then a calibration curve was plotted taking concentration in ?g/ml on x axis and absorbance on y axis.

Evaluation of tablets4-8

Uniformity of Weight (Weight Variation)

Ten tablets were selected at a random and average weight was determined. Then each tablet was weighed individually and the individual weight was compared with an average weight (Wensar).

Weight Variation =   ((Iw-Aw))/Aw   ×100%

Where,

Iw is referred as Individual weight     ,     

Aw is referred as Average weight

Hardness

Tablet hardness test is also known as Crushing Strength Test and the tablet crushing load, which is the force required to break a tablet by compression in the radial direction, was determined using a VinSyst Manual Tablet Hardness Tester (Monsanto hardness tester).

Tablet hardness is checked to ensure that disintegration time and dissolution profile are within range or according to specifications. It is performed to ensure that tablets are strong enough to remain intact during coating, blistering, packing and transportation.

Limit:

Oral tablets have a hardness of 4 to 10 kg.

Friability

Friability of tablets was measured by using Roche Friabilator. Friability was evaluated from the percentage weight loss of 20 tablets tumbled in a friabilator at 25 rpm for 4 minutes. The tablets were dedusted, and the loss in weight caused by fracture or abrasion was recorded as the percentage weight loss (Rolex India).

Friability =   ((Iw-Fw))/Iw   ×100 %

Where,

Iw is referred as Initial weight and Fw is referred as Final weight

Limit:

Friability below 1% was considered acceptable.

Disintegration time9-11

The process of breakdown of a tablet into smaller particles is called as disintegration. A disintegration test is performed in-vitro to ensure that after taking medicine it will release active pharmaceutical ingredients in the stomach or intestine and will be absorbed to give pharmacological effect. This test is also performed to ensure the bioavailability of drugs.  The in-vitro disintegration time of a tablet was determined using disintegration test apparatus as per I.P. specifications. Place one tablet in each of the 6 tubes of the basket. Add a disc to each tube and run the apparatus using 0.1 N HCl for 2 hrs and then phosphate buffer pH 6.8 for 1 hr. The assembly should be raised and lowered between 30 cycles per minute. The time in seconds/minutes taken for complete disintegration of the tablet with no palpable mass remaining in the apparatus was measured and recorded.

In vitro Dissolution Study12-15

The dissolution study was performed for marketed aspirin gastro resistant tablet formulation, by using digital dissolution apparatus, paddle method. The dissolution medium was 0.1 N HCl for 2 hrs and then phosphate buffer pH 6.8 for 1 hr (900 mL, 37 ± 0.5°C). The dissolution rate was studied at 50 rpm using paddle method. Aliquot of dissolution medium was withdrawn at specific time interval, filtered off and the absorbance was measured spectrophotometrically at 227 nm by UV spectrophotometer.

RESULTS AND DISCUSSION16-21

Construction of Standard Curve

The aspirin pure drug was dissolved in ethanol and diluted suitably with distilled water to get the concentration of 1-10 µg/mL and the analysis of the sample was done using 1cm sample cell and scanning at 227 nm using double beam UV-Visible spectrophotometer (Table 2) and the calibration curve (Fig. 1) was constructed.

       
           
       
    Fig 1: Standard Curve for Aspirin

Comparative Study Data for Evaluation of Tablets

The evaluation tests for all the brands of Aspirin tablets were determined and the observed results were shown on Table 3.

Weight Variation

The weight variation of three marketed brand was ranges from 0.3841% to 0.3654%. Hence all brands have been passed with the weight variation test as per IP limit.

Hardness Test

The hardness of presently studied aspirin tablets was ranges from 5.5 kg/cm2 to 8.0 kg/cm2and all the brands have been adhered to the IP specification.

Friability Test

The friability of marketed brands aspirin tablets was ranges from 0.61 % to 0.76 %. So the above brand tablets have agreed the friability test as per Pharmacopeial limit.

Disintegration Test

There is no disintegration was found in first 2 hrs in 0.1N HCl acid medium and the medium was changed in to phosphate buffer (pH 6.8). Hence, the disintegration time of 3 different marketed brands was ranges from 2.15 minutes to 2.75 minutes and complied with the disintegration test limit as per IP specification.

In vitro Dissolution Study

Comparison of in-vitro dissolution profiles (Table 4) of the three brands of aspirin gastro resistant tablets were illustrated in Figure 2. The in vitro dissolution in 0.1N HCl acid media for 2 h discovered no indication of drug release, whereas more than 85 % of drug released in all the brands evaluated within 1 hr, which complies with USP and BP specifications of more than 80 %. Such above observation and report is predicted, as these enteric coats have revealed the similar effect in previous reports.

       
           
       
    Table 4: Dissolution study data

       
           
       
    Fig 2: Graph for Dissolution Study

CONCLUSION: