抗生素英文课件精品Drugsand the Elderly Practical .ppt

Drugs and the Elderly:Practical Considerations C. Bree Johnston MD MPH SF VAMC/UCSF Copyright May 2001 Overview Scope of the issue Pharmacokinetics Pharmacodynamics Adverse drug reactions and adherence Underuse of drugs Nonprescription and alternative therapies Common sense solutions Prescription Drugs Elderly account for 1/3 of prescription drug use, while only 13% of the population Ambulatory elderly fill between 9-13 prescriptions a year (new and refills) One survey: Average of 5.7 prescription medicines per patient Average nursing home patient on 7 medicines Costs of Drugs Medicare does not pay for prescription drugs Average prescription drug cost for an older person is $500/year, but highly variable Nonprescription drugs and herbals can be quite expensive Many Medicare Managed Care Plans have dropped or severely limited drug coverage Drugs cost more in US than any other country New drugs cost more Non-prescription Drugs Surveys indicate that elders take average of 2-4 nonprescription drugs daily Laxatives used in about 1/3-1/2 of elders - many who are not constipated Non-steroidal anti-inflammatory medicines, sedating antihistamines, sedatives, and H2 blockers are all available without a prescription, and all may cause major side effects Pharmacokinetics Decrease in total body water (due to decrease in muscle mass) and increase in total body fat affects volume of distribution Water soluble drugs: lithium, aminoglycosides, alcohol, digoxin Serum levels may go up due to decreased volume of distribution Fat soluble: diazepam, thiopental, trazadone Half life increased with increase in body fat Pharmacokinetics  Absorption: Not highly impacted by aging Variable changes in first pass metabolism due to variable decline in hepatic blood flow (elders may have less first pass effect than younger people, but extremely difficult to predict) Pharmacokinetics and the Liver Acetylation and conjugation do not change appreciably with age Oxidative metabolism thro