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Various Analytical Methods for the Determination of Terazosin in Different Matrices

Alankar Shrivastava

Department of Pharmaceutics, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh, Uttar Pradesh, India

Abstract: Terazosin is used in men for symptom relief in the case of benign prostatic hyperplasia. This is categorized under the group of alpha one adrenoreceptor blockers. Terazosin is also used in high blood pressure by relaxing blood vessels so that blood can easily pass through. In this systematic review different analytical methods for the determination of terazosin in different matrices are discussed. Overall thirty six different analytical methods for the determination of terazosin were found in literature survey, 12 spectrophotometry, 2 TLC, 2 HPTLC, 16 HPLC and 4 electroanalytical methods were found. Advantages and disadvantages of available methods are also discussed. This review also adds knowledge about the place of terazosin therapy in hypertension or enlarged prostate. This review is useful for the researchers involved in the development of new analytical method or formulation.

Keywords: Terazosin, spectrophotometry, chromatography, HPLC, HPTLC, method validation

Received August 21, 2013; Revised November 09, 2013; Accepted December 08, 2013

Citation: Alankar Shrivastava, Various Analytical Methods for the Determination of Terazosin in Different Matrices. World Journal of Analytical Chemistry, 1 (4). 80-86. January 2013. doi:10.12691/wjac-1-4-7

1. Introduction

Lower urinary tract symptoms (LUTS) in elderly men were traditionally attributed to the enlarging prostate. The mechanisms invoked were one or all of the following: histologic benign prostatic hyperplasia (BPH), benign prostatic enlargement (BPE), or benign prostatic obstruction (BPO). [1] These symptoms associated with BPH are known as lower urinary tract symptoms (LUTS). Symptoms of BPH affect 50% of men older than 60 years and almost 90% of men older than 90 years [2].

Benign prostate hyperplasia (BPH) is a urological disorder caused by the noncancerous enlargement of the prostate as men age. As the prostate enlarges, it can constrict the urethra, inducing various symptoms including a weak urinary stream, incomplete bladder emptying, nocturia, dysuria and bladder outlet obstruction. [3] In benign prostatic hyperplasia (BPH) there will be a sudden impact on overall quality of life of patient. [4] BPH is rarely life threatening, but it can lead to acute urological problems, for example acute urinary retention (AUR) [5].

In humans, the prostate lies immediately below the base of the bladder surrounding the proximal portion of the urethra and consists of canals and follicles lined with columnar epithelial cells and surrounded by a fibromuscular stroma consisting of connective tissue and smooth muscles. In the large scale Multinational Survey of the Aging Male, 34% of men in the USA and 29% of European men aged 50–80 years reported moderate to severe LUTS. LUTS and sexual dysfunction are common and important health concerns of men aged ≥ 50 years [6].

α₁-Adrenergic receptors (AR) mediate many of the physiological functions of the endogenous catecholamine’s noradrenaline and adrenaline such as smooth muscle contraction or cellular hypertrophy. Moreover, they are the molecular target for clinically used drugs for the treatment of e.g. arterial hypertension or BPH [7].

α-Adrenoreceptor antagonists are frequently used to treat patients with LUTS and benign prostatic enlargement because of their significant effect on storage and voiding symptoms, QOL, flow rate, and post void residual urine volume. [8] The α₁-blockers reduce smooth muscle tone in the prostate and result in rapid improvements in urinary symptoms and flow [9].

The greatest safety concern associated with the use of these agents is the occurrence of vasodilatory symptoms such as dizziness and orthostatic hypotension resulting from inhibition of α₁-ARs in the systemic vasculature. [10] However Rossitto et al [11] recommended in their publication to use alpha one blocker therapy in a patient having both hypertension and BPH.

Terazosin hydrochloride dehydrate [12] RS-1-(4-amino-6, 7-dimethoxy-2-quinazolinyl)-4-[(tetra-hydro-2-furanyl) carbonyl]- piperazine monohydrochloride [Figure 1] is a α1-adrenoceptor blocker with a long lasting action. [13] This is official in European Pharmacopoeia [12], USP [13], BP [14] and indicated in mild to moderate hypertension and benign prostatic hyperplasia [15]. It is used in the management of hypertension and in benign prostate hyperplasia to relieve symptoms of urinary obstruction.[16] Terazosin is rapidly and almost completely absorbed from the gastrointestinal tract after oral administration and is extensively metabolized in the liver to yield piprazine and three other inactive metabolites. Absorption is not affected by the presence of food. The major route of elimination is via the biliary tract and the drug is excreted in faeces (60%) and urine (40%). Around 10% is excreted as the parent drug and the remainder as its metabolites. Renal impairment shows no significant effect on pharmacokinetics. [17] Terazosin also shown more effective relief and fewer adverse events than those treated with placebo in the patients with female lower urinary tract symptoms (LUTS) [18].

Figure 1. Chemical structure of terazosin hydrochloride dehydrate

Thus this is clearly evident that Terazosin is one of the important alpha one adrenoreceptor blocker for BPH. This forms the basis of our study. In this systematic review different analytical methods available in the current literature for the determination of Terazosin in different matrices are reported. The presented review will be useful for the researchers involved in development of analytical methods of terazosin or formulations.

In this literature survey twelve different spectrophotometric, twenty chromatographic and four electroanalytical methods for terazosin determination in various different matrices were found. Overall aim of the presented review is to benefit scientific community with the knowledge of analytical methods of terazosin determinations.

2. Results [Analytical Methods]

Analytical methods for the determination of terazosin were searched for in various reputated database like Sciencedirect, Pubmed, Medknow, NCBI, Taylor and Francis and Google scholar were explored by using keywords “Analytical methods for terazosin”, “Determination of terazosin”, “Spectrophotometric method for terazosin determination, “Chromatographic method for terazosin determination”, “Electroanalytical methods for determination of terazosin”.

2.1. Spectrophotometric Methods

Spectrophotometry is essentially a trace- analysis technique and is one of the most powerful tools in chemical analysis.[19] Spectrophotometric techniques remain a frequent choice for routine analyses as they provide simple, accurate and inexpensive solutions when compared to other methods.[20] Spectrophotometric tools, and consequently the methods for interpretation of spectrophotometric data, are of increasing importance for analytical laboratories, as well as for environmental, biomedical and industrial monitoring [21].

Spectrophotometric methods are among the oldest methods of analytical chemistry. The absorption of visible light by certain chemical substances has long been used for visual determination of their substances. The term “colorimetry” was used for those analytical methods, in which chemical elements were determined by comparing the color of unknown samples with appropriate standards, either in graduated cylinders or in visual comparators.[22] Application of derivative technique of spectrophotometry offers a powerful tool for quantitative analysis of multi-component mixtures. Derivative spectroscopy (DS) has been directly used for the simultaneous determination of organic and inorganic compounds [23].

Summary of different spectrophotometric methods for the determination of terazosin is provided under Table 1.

Other than methods presented in the Table 1, negative results of simultaneous determination of TRZ with other alpha one adrenoreceptor blockers[31] is also available. Another method proposed is based on the conversion of the analyte (terazosin) in the form of an ion associated complex formed with zinc thiocyanate by a filter and a detectable species by x-ray spectrometry.[32] The linear dynamic range and detection limit reported was 0.732×10⁻³ to 1000 mg/ml and 0.732 μg/ml respectively.

2.1.1. Comparison

Specrofluorimetry as an analytical tool provides a well defined identity of the compounds present in the sample on the basis of their unique fluorescent nature. The compounds can be analysed upto the levels of nanograms. [33] Spectrofl uorimetry is considered a sensitive and simple technique. [34] The acid-dye method can provide a more sensitive technique for certain amines and quaternary ammonium compounds that absorb weakly in the ultraviolet region. [35] In the case of Terazosin spectrofluorimetry method proves to be more advantageous in case of sensitivity. Acid-dye or methods based on ion pair complex are less sensitive and requires extraction from respective solvents after reaction.

Table 1. Summary of spectrophotometry methods

2.2. Chromatography

Chromatography presents one of the greatest methodological phenomenon of the twentieth century with an extremely fruitful output for the future. Chromatography was realized for the first time as an analytical “technological” process over a hundred years ago, but only in the more recent decades, investors have noticed that many natural processes are in fact chromatographic [36]. Chromatography is a proven method for separating complex samples into their constituent parts, and is undoubtedly the most important procedure for isolating and purifying chemicals. [37] Chromatographic methods are commonly used for the quantitative and qualitative analysis of raw materials, drug substances, drug products and compounds in biological fluids [38].

High-performance liquid chromatography (HPLC) was introduced to pharmaceutical analysis not long after its discovery in the late 1960s. By now it has developed into a generally applicable analytical method providing rapid and versatile separation possibilities that meet the increasing requirements for purity testing of bulk pharmaceuticals and pharmaceutical products [39].

HPTLC is a sophisticated instrumental technique based on full capabilities of TLC. The advantages of automation scanning, full optimization, selective detection principle, minimum sample preparation, hyphenation etc., enable it to be powerful analytical tool for chromatographic information of complex mixtures of organic, inorganic and biomolecules. [40] HPTLC is a valuable tool for reliable identification because it can provide chromatographic fingerprints that can be visualized and stored as electronic images [41].

Summary of chromatographic methods and summary of methods for determination of terazosin in different combinations are presented under Table 2 and Table 3 respectively.

2.2.1. Comparison of Chromatographic Methods

Different chromatographic methods including 2 TLC[42], 2 HPTLC[43,44], 4 HPLC-F[45,46,47,48] and 11 HPLC-UV[12,13,44,49,50,51,52,53,54,55,56] methods for the determination of Terazosin in different matrices is available in current literature.

Fluorescence has allowed liquid chromatography (LC) to expand into a high-performance technique. High-performance liquid chromatography (HPLC) procedures with fluorescence detection are used in routine analysis for assays in the low nanogram per milliliter range and concentrations as low as picogram per milliliter often can be measured.[57] Fluorescence-based HPLC has been used as a sensitive and less costly alternative approach to LC-MS.[58] This may be the reason that no direct LC-MS method is available. Here in the case of comparison of chromatographic methods of Terazosin, HPLC-F methods [45,46,47,48] seem to be quite sensitive methods as compared to other chromatographic methods.

Table 2. Summary of chromatographic methods of Terazosin in different matrices

Table 3. Summary of chromatographic methods of Terazosin in combination with other drugs

3. Electroanalytical Methods

Modern electrochemical methods are now sensitive, selective, rapid, and easy techniques applicable to analysis in the pharmaceutical fields, and indeed in most areas of analytical chemistry. They are probably the most versatile of all trace pharmaceutically active compound analysis. [59] Electrochemistry has always provided analytical techniques characterized by instrumental simplicity, moderate cost and portability. [60] Electroanalytical techniques can easily be adopted to solve many problems of pharmaceutical interest with a high degree of accuracy, precision, sensitivity and selectivity, often in a spectacularly reproducible way by employing this approach [60,61].

Four electoanalytical methods [14,62,63,64] were found during literature survey.

4. Conclusion

Different analytical methods (n=36) for determination of terazosin were discussed in this presented review. 12 spectrophotometry, 2 TLC, 2 HPTLC, 16 HPLC and 4 electroanalytical methods were found in literature survey. Advantages and disadvantages of different methods e.g. spectrophotometery, chromatography [HPLC and HPTLC] and electroanalytical methods were also discussed. Details of spectrophotometry and electroanalytical methods are provided in Table 1 and Table 4 respectively. Table 2 and Table 3 represents different chromatographic methods of terazosin in different matrices. This article is useful for the scientists involved in the research related to terazosin particularly in the areas of method development or development of new formulations. This review also provides a brief knowledge of place of terazosin in hypertension and benign prostatic hyperplasia which can be compared to other drugs available in same indication.

Table 4. Summary of electroanalytical methods

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