The outbreak of COVID-19 in Wuhan, China in December 2019, resulted in the evolution of a global pandemic which caused thousands of deaths worldwide. As little was known about this new coronavirus, many existing drugs were repurposed with the goal to effectively treat the infection. Two such candidates were dexamethasone (DEX) and N-acetyl-L-cysteine (NAC). Relatively few articles have been published relating to their electrochemical determination, and in this project the use of metal nanoparticles, microparticles and films alongside various carbon nano-onions (CNOs) were explored as chemical modifiers in order to maximize their electrochemical responses. Bare, copper microparticle (CuMPs) and copper film (CuF) modified glassy carbon electrodes were exploited in Chapter 2 to examine the DEX electroreduction response, resulting in sensitivities of 2.00 × 102 μA cm-2 mM-1 and 1.13 × 102 μA cm-2 mM-1 for the CuF and CuMP modified GCEs respectively. Pharmaceutical samples in the form of a cream and a solid-state dose, were analysed with recoveries 77.46 – 87.91 %, with 1.93 – 4.97 % variance. Various types of CNOs were electrochemically characterised of which, oxi-BN-doped-CNOs was selected and combined with gold nanoparticles (AuNPs), resulting in an AuNP/oxi-BN-doped CNO/GCE for NAC quantitation (sensitivity 476 μQ cm-2 mM-1 in acetate buffer). Following design and optimisation, a solid dose form of NAC was quantitatively analysed, resulting in 89 – 105 % ± 6.75 % recovery, thus validating the sensors.