Taking 600mg ibuprofen 3x day and colchicine for pericarditis & beta blocker for tachicardia. how dangerous are nsaids as far as liver/kidney damage?

Mildly so: As with many drugs prolonged use, especially in high doses can harm kidneys or liver. It is important to monitor liver and kidney function while taking these drugs. However they are often quite helpful in treating the pericarditis so i would certainly stay on them as long asneeded to control symptoms and stop thereafter.

Not bad: When used temporarily, the biggest risk is of gastritis (acid-related) from nsaid's. Long-term risks of renal dysfunction are associated with routine NSAID use over several years. See your doctor for appropriate management.

See below: All medications are potentially dangerous.You only take them considering risks and benefits. Nsaid's are known to cause kidney and liver problems and their effect should be monitored. If your medical problem requires the therapy with no other good options , you take the medication.