Final answer:
High or low potassium levels can be a potential contraindication for drugs that inhibit the CYP450 system.
Step-by-step explanation:
A potential contraindication for drugs that inhibit the CYP450 system is high or low potassium levels. These drugs can affect potassium-sparing diuretics, which are used to treat hypertension. The inhibition of the CYP450 system can lead to an imbalance in potassium levels, which can have negative effects on the body.