The danger of polymedication is mainly due to the fact that different physicians prescribe different medications for different ailments, which are incompatibie with each other. Older people are particularly at risk.
"In a study by Hoffmann et al., about 70% of nursing home residents consumed five or more drugs per day. This cross-sectional study found that 63.6% of residents had renal insufficiency. The 685 residents received a total of 4,316 medicinal products as long-term medication. Of these, 2,184 (50.6%) had contraindications in patients with impaired renal function or needed a dose adjustement. The drugs most commonly involved were ramipril, simvastatin, and torasemide. Metformin, ramipril, and potassium chloride were particularly frequently overdosed.
Too high a level of cholesterol-lowering statins can cause myopathies and, in the worst case, rhabdomyolysis, i.e. the breakdown of muscle tissue. High doses of diuretics increase the risk of gout and diabetes and diturb the electrolyte balance. Too high a potassium level can cause life-threatening arrhythmias. When ACE inhibitors are taken in addition to potassium, the risk of hyperkalaemia increases dramatically."
Source: DocCheck News 17.47 from 24. November 2017