Olanzapine (OLZ) and lithium carbonate (Li2CO3) are the main drugs for treating mental disorders related to dopamine (DA). A highly conductive carbon paper sensing electrode is used to investigate the effects of OLZ and Li2CO3 on DA oxidation due to its amplification of oxidation peak currents. Different chemical properties of drugs have different effects on DA oxidation. The presence of OLZ fouling on the electrode surface due to the irreversible adsorption weakens the sensing activity and thus reduces the DA oxidation peak current. However, the fixed DA oxidation peak potential at 0.22 V indicates no interaction between them. The hydrolysis effect of Li2CO3 increases the solution pH from 7.47 to 9.73, which promotes the deprotonation of DA, leading to a 156 mV negative shift of the DA oxidation peak potential. Additionally, a 94% decrease of the DA peak current may be related to the generation of polydopamine in alkaline media.