CYP2D6 and cardiomyopathy: Although there are reports of VEN-associated CTOX cardiomyopathy in patients with a CYP2D6 lack of function genotype (poor metabolizer) [16,17,18], no strong correlation has been demonstrated between the CYP2D6 or CYP2C19 genotypes and VEN or O-Desmethyl-VEN plasma levels, nor with the efficacy or safety of VEN therapy.