Because antidepressants and antipsychotics are commonly described in combination with drugs used to treat comorbid psychiatric or somatic disorders (e.g. anxiolytics, mood stabilizers, cardiovascular drugs, antimicrobial agents), they may be involved in drug interactions. Furthermore, agents such as lithium and atypical antipsychotics may be used to augment the antidepressant response in cases of refractory depression. Based on their mechanisms, drug-drug interactions can be classified either as pharmacokinetic or pharmacodynamic in nature. The well-documented risk of potentially harmful pharmacodynamic drug interactions with first-generation anti-depressants, e.g. monoamine oxidase inhibitors (MAOIs), with regard to the induction of the serotonin syndrome, has contributed to a gradual decline in their use in clinical practise. Second- and third-generation antidepressants have gradually replaced tricyclic antidepressants (TCAs) and MAOIs, mainly because of their improved tolerability and safety profile. The second- and third-generation antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs) and other compounds with different mechanisms of action. These drugs and also the majority of antipsychotics are metabolized in the liver by the cytochrome P450 (CYP) enzyme system. Therefore, the use of these compounds may be associated with clinically relevant pharmacokinetic interactions with other medications. The knowledge about the CYP metabolism of drugs may be used to guide the selection of an antidepressant or an anti-psychotic with a low drug-drug interaction potential for an individual patient. The aim of the present article is to review drug-interaction potentials with specific focus on second-generation antidepressants (SSRIs), newer antidepressants (SNRIs: venlafaxine and duloxetine; bupropion, mirtazapine, trazodone), novel atypical antidepressants (agomelatine), as well as new generation atypical antipsychotics (aripiprazole, paliperidone).