The article gives an overview of traditional classification of epidemiological study designs as well as study designs based on modern epidemiology. Epidemiology is the study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems.The choice is often between validity, i.e. obtaining the most accurate answer, and feasibility, i.e. obtaining an answer.When the individual is the unit of analysis and the disease outcome under study is dichotomous, then epidemiological study designs can best be classified according to two criteria: (i) the type of outcome under study (incidence or prevalence) and (ii) whether there is sampling on the basis of the outcome. Once this two-dimensional classification system has been adopted, then there are only four basic study designs (i) incidence studies; (ii) incidence case - control studies; (iii) prevalence studies; and (iv) prevalence case - control studies (Rothman et al). Continuous outcome measures using longitudinal and cross sectional studies have been mentioned.

Transdermal Drug Delivery System is the system in which the delivery of the active ingredients of the drug occurs through the skin. Transdermal drug delivery system can improve the therapeutic efficacy and safety of the drugs because drug delivered through the skin at a predetermined and controlled rate. Skin is the important site of drug application for both the local and systemic effects. Skin of an average adult body covers a surface of approximately 2 m2 and receives about one-third of the blood circulating through the body. Skin is an effective medium from which absorption of the drug takes place and enters the circulatory system. Transdermal patch is a medicated adhesive patch that is placed on the skin to deliver the drug through the skin in order to achieve systemic absorption of drug at a predetermined rate over a prolonged period of time. This review article covers a brief outline of the transdermal drug delivery system, advantages over conventional drug delivery system, Layers of the skin, various components of transdermal patch, penetration enhancers, and evaluation of transdermal system and applications of Transdermal patch.

A simple, Accurate, precise method was developed for the simultaneous estimation of the Metformin and Acarbose in Tablet dosage form. Chromatogram was run through thermo BDS (250mm 4.6mm, 5µ). Mobile phase containing Buffer and Acetonitrile in the ratio of 35:65A was pumped through column at a flow rate of 1ml/min. Buffer used in this method was 0.02N KH₂PO₄ buffer at P^H 3.3. Temperature was maintained at 30ºC. Optimized wavelength for Metformin and Acarbose was 215nm. Retention time of Metformin and Acarbose were found to be 2.8min and 4.0min. %RSD of the Metformin and Acarbose were found to be 0.65 and 0.9 respectively. %Recover was Obtained as 99.83% and 99.97% for Metformin and Acarbose respectively. LOD, LOQ values are obtained from regression equations of Metformin and Acarbose were 0.4ppm, 1.3ppm and 0.8ppm, 2.5ppm respectively. Regression equation of Metformin is y = 13779x + 1840, and of Acarbose is y = 16828x + 4143. 

A simple, accurate, precise, sensitive, rapid UPLC method has been developed and validated for determination of Olmesartan medoxomil and Cilnidipine in its pharmaceutical dosage form. Chromatographic separation was achieved on a BEH C18 column (100 ×2.1mm,1.7), by a mobile phase consisted of Ph3.5 buffer, maintained with Roth phosphoric acid and methanol in 35:65(V/V) ratio with a flow rate of 0.3 ml/min. The detection wavelength was set at 254 nm. Olmesartan medoxomil and Cilnidipine was subjected to different stress conditions. The degradation products, when any, were well resolved from the pure drug with significantly different retention time values. The method was linear (r = 0.999) at a concentration range of 0.2-0.3 μg/ml. The intra and inter day precisions were satisfactory the relative standard deviations did not exceed 2%. The accuracy of the method was proved the mean recovery of Olmesartan medoxomil and Cilnidipine was 99.04-101.58%. The proposed method has high throughput as the analysis involved short run-time (3.20 mines). The method met the ICH/FDA regulatory requirements. The proposed method was successfully applied for the determination of Olmesartan medoxomil and Cilnidipine with acceptable accuracy and precisions. The results demonstrated that the methodcan be applied successfully for routine use in quality control industry laboratories. 

The aim of the study was to investigate the feasibility of using niosomes as a drug delivery system for Methotrexate. By entrapment of drug in niosomes, dose also could be reduced. Niosomes were prepared by thin film hydration technique with rotary flash evaporator in the micro molar ratio of cholesterol and surfactant. Particle size, zeta potential, entrapment efficiency and in vitro drug release studies were performed. From the results of the present Methotrexate experimental investigation, it may be concluded that formulation MNF10 containing drug with 150:100(surfactant: cholesterol) ratio was showing small vesicles size, high percentage of entrapment with the desired sustained release of Methotrexate.