Carbamazepine is chemically related to the tricyclic antidepressants. It is a derivative of iminostilbene with a carbamoyl group at the 5 position; this moiety is essential for potent antiseizure activity [1, 2]. Carbamazepine, 5H di benzo (b, f) azepine-5-carboxamide (fig. 1), is an antiepileptic drug and is the drug of choice for the treatment of grand mal and psychomotor epilepsy. It is considered to be one of the most vital drugs for the relief of pain associated with trigeminal neuralgia [3-4]. It is a white or almost white, crystalline powder, practically insoluble in water, freely soluble in methylene chloride, sparingly soluble in acetone and alcohol, and practically insoluble in ether. It shows polymorphism. Carbamazepine is official in IP, USP, BP, etc [5, 6]. According to the investigation of literature, UV spectro-photometric and HPLC analytical methods were developed at different wavelengths for the analysis of Carbamazepine in plasma fluids, human serum, plasma, and pharmaceutical tablet dosage form or bulk drug sample. [7-11]. The rationale of this work is to develop a simple, accurate, rapid, precise, reproducible, and cost-effective Spectrophotometric method for the direct quantitative determination of carbamazepine. There are several dosage forms of carbamazepine available on the market, including chewable tablets, suspension, sustained-release capsules, and sustained-release tablets [12]. The Beer-Lambert law is the main principle governing Spectrophotometric quantitative analysis [13-15]. Carbamazepine (CBZ) is an anticonvulsant medication used for the treatment of seizures, bipolar disorder, neuropathic pain, neuralgia, and trigeminal. It works by diminishing nerve impulses that cause seizures and pain. The available carbamazepine dosage forms in the market are chewable tablets, suspension, sustained-release capsules, and sustained-release tablets.

       
           
       
    Fig 1: Chemical structure of Carbamazepine

MATERIALS AND METHODS

Materials

Carbamazepine (API), Tegreto 200 mg tablets, ethanol, sodium hydroxide and Water HPLC Grade

Instruments

UV-Visible spectrophotometer with UV Win software, Electronic Balance, Biotech’s Ultra Sonicator, pH meter, Water bath shaker, Centrifuge and Refrigerator

METHOD DEVELOPMENT

Preparation of a standard stock solution

A precise quantity of 10 mg of carbamazepine was measured and transferred into a 10 mL volumetric flask. It was then dissolved in a minimal amount of ethanol until complete solubility was achieved. The solution's volume was subsequently adjusted to the calibration mark using 0.1N NaOH, yielding a standard stock solution with a concentration of 1000 ?g/ml. To create a 100 ?g/ml concentration from this initial stock solution, 1 mL was pipetted and moved to a 10 mL volumetric flask, followed by the addition of sodium hydroxide to achieve the final volume, resulting in the preparation of the second standard stock solution.

Selection of wavelength for analysis of carbamazepine

A 10 ml volumetric flask was accurately filled with 1 ml of standard stock solution-2, which was subsequently diluted to a total volume of 10 ml using sodium hydroxide, resulting in a concentration of 10?g/ml. This prepared stock solution was utilized for an initial spectral scan within the UV range of 200-400 nm to identify the maximum wavelength.

Preparation of a sample solution

A precise measurement was taken of ten tablets, and their average weight was determined before they were ground into a fine powder. The powder corresponding to 10 mg of carbamazepine was then dissolved in ethanol with the help of sonication. The solution was adjusted to a total volume of 10 ml in a volumetric flask using sodium hydroxide, resulting in a concentration of 1000 ?g/ml. The amount of carbamazepine in the commercially available formulation (Tegreto 200 mg) was assessed using a pre-validated method.

Assay

%Assay =(Sample absorbence)/(Stad.absorbence)×(Weight of standard)/(Dilution of standard)×(Dilution of sample)/(Weight of sample)×Purity/100×(Weight of tab.)/(Label claim)×100

According to ICH Q2 (R1) and USP criteria, the suggested technique was validated for a number of parameters, including linearity, accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), robustness, ruggedness and stability studies [19-20].

Linearity

Serial dilutions were performed from the standard stock-2 solution to obtain concentrations of 2?g/mL, 4?g/mL, 6?g/mL, 8?g/mL, and 10?g/mL. The absorbance of each concentration was measured at 285 nm. A calibration curve was generated by plotting absorbance on the y-axis and concentration on the x-axis.

Precision

Six replicate measurements were conducted on the homogeneous solution to assess the precision of the method, focusing on both repeatability (intraday precision) and intermediate precision (interday precision) for the reference solution at a concentration of 8?g/mL. To enhance the accuracy of the method, three replicates were introduced into the system on the same day. The results were then calculated as the percentage of the relative standard deviation (RSD).

Accuracy

A recovery study for carbamazepine was conducted at concentrations of 50%, 100%, and 150%. The findings are presented in the table below. It was observed that there were no drug-drug interactions, drug-excipients interactions, or drug-solvent interactions identified. Therefore, it has been confirmed that none of the components interfere with the drug.

LOD and LOQ

The detection limit of an analytical method indicates the smallest amount of an analyte present in a sample that can be recognized, even if it cannot be measured accurately. On the other hand, the quantification limit is the minimum concentration of an analyte that can be measured reliably and with sufficient accuracy in a specific analytical process.

Robustness

The robustness of this procedure was evaluated by measuring the absorbance of a 6?g/mL carbamazepine standard solution at different maximum wavelengths (specifically ±1nm) around the actual maximum.

Ruggedness

The assessment of ruggedness was conducted by analyzing data collected from various analysts, each utilizing different reagents and instruments.

Stability

Stability of carbamazepine sample solution was determined initially and 24 hours later, the % assay was compared.

RESULTS AND DISCUSSION

Linearity

The range of the linearity concentration for carbamazepine was 2–10 ?g/mL shown in Table 2. Fig 3 displayed the calibration curve and the calculation of the correlation coefficient, intercept, and slope of carbamazepine.

Table.2. Linearity of carbamazepine at 285 nm & Statistical Data

The precision study showed no significant differences in precision values, confirming the method's suitability for analyzing carbamazepine in tablet formulations. There was no evidence of interference from excipients. Results ranged from 98.33% to 100.56%, with an acceptable deviation of 2%.

The LOD (Limit of Detection) was estimated from the set of 6 calibration curves used to    determine method linearity. The LOD may be calculated as

LOD = 3.3 × (S.D./Slope)

Where,

SD = Standard deviation of the Y- intercepts of the 6 calibration curves

Slope = Mean slope of the 6 calibration curves

The LOQ (Limit of Quantization) was estimated from the set of 6 calibration curves used to determine method linearity.

The LOQ may be The LOQ may be calculated as

LOQ = 10 × (S.D./Slope)

Where SD = Standard deviation of the Y- intercepts of the 6 calibration curves

Slope = Mean slope of the 6 calibration curves

The assessment of ruggedness was conducted by analyzing data collected from various analysts, each utilizing different reagents and instruments. Each analyst prepared six samples from the same batch, and the resulting data is presented in the table.

Table.5.Ruggedness of Carbamazepine

Recovery study for carbamazepine was carried out at 50%, 100%, and 150% concentration. The results were shown in the table using the data below. Drug-drug interaction, drug excipients interaction, and drug solvent interaction have not been noticed or identified. Hence, it has been proved that there is no interference of any component with the drug.

The robustness of this procedure was evaluated by measuring the absorbance of a 6?g/mL carbamazepine standard solution at different maximum wavelengths (specifically ±1nm) around the actual maximum.

To check the stability of the solution, a sample solution of carbamazepine with a concentration of 6?g/mL was taken. In table 8, stability studies information was displayed

CONCLUSION: