A method for simultaneous quantitation of lidocaine orphenadrine, chlorpheniramine and chloroquine on GC-MS using the modified QuEChERS extraction technique was developed and validated. Brucine was used as an internal standard. Separation was achieved on GC-MS (Agilent-7890A/5975, capillary column DB-5, 15m x 250μm x 0.25μm, splitless, run time 14.75min) using helium as carrier gas. Selected ion monitoring (SIM) mode was used for the quantitation. LOQ for all the analytes was 100μg/L. Method demonstrated a good linearity range (r²>0.995) for all analytes from 100 to 1000μg/L. No interference from the matrices was observed. Method depicted a recovery of above 90% for all the analytes. Validated method was successfully applied for quantitative analysis of these drugs in real case samples (i.e. liver, blood and urine). Quantitated concentrations of chloroquine and orphenadrine fell in fatal range while those for lidocaine and chlorpheniramine fell in non-fatal range in real case samples. Current method is quick, easy, cheap, robust and reproducible. Current method is found to be an excellent tool for simultaneous monitoring of these therapeutic drugs commonly encountered in cases received in forensic toxicology labs.