INTRODUCTION:

Spironolactone is chemically (17-hydroxy-7α-mercapto-3-oxo-17α-pregn-4-ene-21-carboxylic acid γ-lactone acetate) Fig,1 [1,2,3]. Spironolactone is most commonly used anti-diuretic agent in clinical practices. Spironolactone site of action is intracellular aldosterone receptors in the distal tubule cells. This increases the excretion of water and sodium and decreases the excretion of potassium [4,5,6]. Spironolactone has ant androgen activity by binding to the androgen receptor and preventing it from interacting with dihydrotestosterone.[7]

Fig1. Chemical structure of Spironolactone

The purpose of stability testing is to provide evidence on how the quality of a drug substance or drug product varies with time under the influence of a variety of environmental factors. [8]Initial improvement process, forced degradation activities must be executed to ensure that the process is selective to save lot of time, effort, money and to find out the responsible conditions for drug degradation. [9]

The main reason of degradation are the chemical instability of the drug substance under the conditions of heat, humidity, solvent, pH, and light encountered during manufacture, isolation, purification, drying, storage, transportation, and/or formulation is main cause of its degradation. [10]

The method of analysis is based on the measuring in the near (UV) ultraviolet path of spectrum (200-400 nm). UV Spectrophotometry can be used for stress-degradation studies of Spironolactone. The active pharmaceutical ingredient is subjected to a number of forced degradation conditions to include acidic, basic and photo conditions as per ICH guidelines (Q1 A and Q1B)[11]. Forced degradation should be one of the activities performed early in the development process to ensure that the method is discriminating before a lot of time, effort, and money have been expended. It is important to determine the conditions responsible to degrade the drug. Literature survey revealed that several High-performance liquid chromatography (HPLC)[7, 12], UPLC [13]methods for stability study of Spironolactone but no report is available for degradation studies of Spironolactone by UV.

Thus, in the present study Ultraviolet-visible (UV-Vis) spectroscopy was used for the analysis of forced degradation of spironolactone, as it is a simple, rapid and cost effective method as compared to HPLC.

Factors affecting forced degradation:

The factors which affect the API for forced degradation are Temperature, humidity, Acid/base stress testing, pH variations, photo degradation.

Thermal and/or Humidity Stress Testing:

Thermal and/or humidity stress testing is performed by keeping the drug substance to thermal/humidity conditions for extended period of time which causes the substance to degrade forcefully to its primary constituents components.

Acid/Base Stress Testing:

Acid/base stress testing is used to evaluate the forced degradation of API. In these test the API is exposed in acidic or basic condition for longer period of time causes degradation to its main constituents. Acid / base hydrolysis take place in labile carbonyl functional groups for e.g. esters (lactones), amides (lactams), alcohols, aryl amines.

Degradation by UV Light:

Many more of UV unstable compounds have a major problem of UV light degradation. UV unstable products which are made up of natural and synthetic polymers as they break or disintegrate when exposed to continuous sunlight. Degradation of compound is dependent on the degree of exposure; nonstop exposure is a more serious problem than intermittent exposure

MATERIALS AND METHODS:

Chemicals:

Spironolactone was supplied by Sanofi Aventis Andheri Mumbai, India. HCL, NaOH was procured from Merck Pharmaceuticals Mumbai All chemicals and reagents were of analytical grade (AR).

Instrumentation:

UV visible Jasco (Japan) double beam spectrophotometer (V 630) attached with computer operated software Spectra manager with spectral width of 2 nm, wavelength accuracy of 0.5 nm and pair of 1 cm matched quartz cells was used to measure UV spectra of drug and dosage formulations. The solvent which are used for the preparations was double distilled water.

Preparation of 0.1 N hydrochloric acid (HCL):

Accurately measured 8.3 ml of concentrated HCL analytical grade was taken and transferred into 100 ml volumetric flask and adjust the volume with the double distilled water up to 100ml flask mark.

Preparation of 0.1 N sodium hydroxide (NaOH):

Accurately weighted 4 gms of NaOH was transferred into 100 ml volumetric flask and dissolve it in small amount of double distilled water and finally make up the volume up to 100 ml flask mark.

Preparation of Spironolactone Stock Solution (Bulk drug):

Accurately weighted 100mg of active Spironolactone was transferred into 100 ml volumetric flask separately and add double distilled water up to 100 flask mark. The strength of solution was 1 mg/ ml. The absorbance of solution 100 ppm concentrations was determined at 237 nm Spironolactone by using blank solution and recorded.

Methods of degradation studies:

For UV light:

Take 5 ml of 100 ppm solution of Spironolactone in different test tubes to study the effect of UV (ultraviolet) light on them. Then add 5 ml of double distilled water and keep these test tubes in UV light for the 30 minutes. After the 30 minutes completions of UV exposure the absorbance of the solutions was analyzed at wavelength 237 nm and spironolactone.

For Acid:

Take 5 ml of 100 ppm solution of Spironolactone in different test tubes to study the effect of acid on them. In same test tubes, add 5 ml of 1 N hydrochloric acid and keep these test tubes aside for the 30 minutes. After the 30 minutes completions the absorbance of the solutions was analyzed separately at wavelength and 237 nm spironolactone.

For Base:

Take 5 ml of 100 ppm solution of Spironolactone in two different test tubes to study the effect of base (NaOH) on them. In same test tubes, then add 5 ml of 1N sodium hydroxide and keep these test tubes aside for the 30 minutes. . After the 30 minutes completions the absorbance of the solutions was analyzed separately at and 237 nm furosemide and spironolactone.

For Heat:

Take 5 ml of 100 ppm solution of Spironolactone in two different test tubes to study the effect of heat on them. In same test tube, than add 5 ml of double distilled water and keep these test tubes in water bath for the 30 minutes at 50^oC. After the 30 minutes completions the absorbance of the solutions was analyzed separately at 237 nm spironolactone by using blank solution and recorded.

Table 1. Absorbance of Spironolactone

Degradation Parameters	SPIRONOLACTONE
	1	2		3	Mean
Before	0.5219		0.5221	0.5221		0.5219
After Acid	0.6606		0.6617	0.6609		0.6610
After Base	0.7016		0.7017	0.7012		0.7015
After Heat	0.6449		0.6453	0.6452		0.6450
After UV	0.4301		0.4315	0.4309		0.4308

Table 2. Degradation Pattern in Percentage of Spironolactone

Degradation Parameters	SPIRONOLACTONE
	1	2		3	Mean
Before	100%		100.03%	100.03%		100%
After Acid	126.57%		126.78%	126.63%		126.65%
After Base	134.43%		133.43%	134.35%		134.41%
After Heat	123.56%		123.64%	123.62%		123.58%
After UV	82.41%		82.67%	82.56%		82.55%

RESULTS AND DISCUSSION:

Degradation studies are essential parameters in the new drug development studies. The purpose of these degradation studies is to ensure the qualities of individual drugs as well as in combination of drug product, during its storage. The qualities of each drug component changes with the time under the exposure of environmental condition such as humidity, temperature and light. The purpose of degradation studies is to investigate those changes, to get a shelf life for the drug product and to find out storage conditions, which will be applicable to all future batches of the tested drug product manufactured and packaged under similar purpose.

We study degradation parameters on active Spironolactone) the absorbances for degradation parameters are given in (Table1. Fig 2) Spironolactone. Spironolactone is subjected to 0.1N NaOH it shows increased availability i.e. 134.41% and in presence of Acid, Heat and UV light it shows 126.65%, 123.58%, 82.55% availability (Fig 3).

Fig 2. Absorbance of Spironolactone

Fig 3: Percentage Degradation Pattern

From our results we can concluded that Spironolactone when introduced in acidic medium i.e. 0.1N HCL it degrade up to 126.65% but degrades to large extend when subjected to basic medium i.e. 0.1N NaOH it degrade up to 134.41%. When Spironolactone exposed to U.V. light degradation was observed i.e. 82.55% and exposed to heat for 30 min it shows 123.58 % availability.

CONCLUSION:

According to WHO monographic specifications the official assay limit of content should NLT 95% and NMT 105% of the estimated potency. The conclusion of our results is that the Spironolactone degrades more when exposed to the basic medium as soon as it also degrades when exposed to basic medium, heat.

ACKNOWLEDGMENT:

Authors are thankful to Dr. C. S. Magdum, Principal, Rajarambapu College of Pharmacy, Kasegaon (Maharashtra) for providing necessary facilities to carry out the research work.

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

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Received on 25.03.2019 Accepted on 30.04.2019

Asian J. Pharm. Tech. 2019; 9(3):185-188.

DOI: 10.5958/2231-5713.2019.00031.X