Table 3. . The ten most common moderate and major drug–drug interactions identified in the Danish and the FDA drug interaction databases. The potential clinical effects and the severity based on clinical significance are from the databases. The minor drug–drug interactions were not included.

Rank	DDI	Number of cases	Potential clinical effect	Severity
1	Furosemide + Metoprolol	13	Hyperglycemia and hypertriglyceridemia	Moderate
2	Furosemide + Pantoprazole	11	Hypomagnesemia	Moderate
3	Furosemide + Sodium picosulfate	9	Fluid and electrolyte disturbances	Moderate
4	Metoprolol + Amlodipine	9	Further reductions in heart rate, cardiac conduction and cardiac contractility	Moderate
5	Clopidogrel + Pantoprazole	8	Reduced bioactivation of clopidogrel and the therapeutic efficacy	Moderate
6	Metformin + Insulin	7	Hypoglycemia	Moderate
7	Mirtazapine + Metoprolol	7	Hypotension	Moderate
8	Furosemide + Insulin	7	Hyperglycemia, glucose intolerance, new-onset diabetes mellitus and/or exacerbation of pre-existing diabetes	Moderate
9	Furosemide + Metformin	7	Increased metformin levels potentially leading to lactic acidosis	Moderate
10	Atorvastatin + Clopidogrel	6	Reduced bioactivation of clopidogrel and its antiplatelet effect	Moderate