Typical unwanted side effects of prescriptions drugs are due to excess drug doses, drug-drug interactions (DDIs), interference with chronic disease and acute interfering disease (eg dehydration).
According to a study reported in 1998 in the Journal of the American Medical Association, adverse drug reactions (ADR's) to prescription and over-the-counter medications are between the fourth and sixth leading cause of all deaths in the USA. The study estimates that in 1994, 2.3 million hospitalised Americans had serious ADRs; 106,000 had fatal ones.
Every day (2019 data), 750 older people living in the United States (age 65 and older) are hospitalized due to serious side effects from one or more medications. Over the ten years since 2010, older people sought medical treatment more than 35 million times for adverse drug events and there were more than 2 million hospital admissions.
In a study of elderly patients, 66.7% of the ADRs were associated with cardiovascular, metabolic, renal or neuropsychological symptoms. The drugs involved were mainly cardiovascular (43.7%) and psychotropic (31.2%) drugs. One or more risk factors (mainly DDIs and/or interfering acute diseases) were recorded in 81.2% of ADRs.
Sickness and death due to medical drugs have been estimated to cost more than $136 billion a year in the US. Approximately 30% of hospital patients experience adverse drug effects, and anywhere between 3%-28% of all hospital admissions are due to medical drugs. Adverse drug effects may account for up to 140,000 deaths annually in the USA.
During a 14 day study carried out at 33 French teaching hospitals, and general hospitals, 100 patients were admitted for adverse prescription drug reaction. 9 of the 100 admissions resulted from gastrointestinal bleeding caused by NSAID's (analgesic pain relievers), and 13 were haemorrhaging due to anticoagulant drugs (blood thinning) drugs. Of the 193 different drugs associated with these admissions, cardiac stimulants and antiarrhythmic drugs were identified as the most common.
With regard to the prescription of the anti-depressant drug Luvox to teenagers in the USA, the American Journal of Psychiatry (September 1991), reported: "Our observations confirm the efficacy of fluvoxamine Luvox in the treatment of depression, but suggest that this drug can induce mania in some patients when it is given at normal doses". Research carried out at the Hadassah-Hebrew University School of Medicine in Jerusalem and published in 1993 also of this side effect.