As we know that most of the drug metabolized into its metabolite by liver but sometimes the metabolite are toxic in nature , continuous exposure to drugs with high doses leads to enzymes downregulatioon (drug metabolizing enzymes) leads to drug induced liver toxicity. Drug Induced Liver Injury (DILI) either idiosyncratic or Dose related affects the liver, I think Liver injury is the prevalent drug related problem.
Despite enter percentage variation between the drug therapy problems and country, as per different research findings, the most common drug-related problems encountering developed countries are seven in number. Namely