Drug | Bolus Administration | Multiple Boluses or Infusion | Comments |
Propofol | 2060% reduction Dose on lean body mass (1 mg/kg in very old patients) | 50% reduction Infusions beyond 50 min progressively increase the time required to decrease the blood level by 50% (but effect site levels may decrease faster in elderly patients) | Possible increased brain sensitivity Decreased Vcen Slowed redistribution |
Thiopental | 20% reduction | 20% reduction | Decreased Vcen |
Etomidate | 2550% reduction | Slowed redistribution | |
Midazolam | Compared to age 20, modest reduction at age 60, 75% reduction at age 90 years | Similar to bolus | Increased brain sensitivity |
Morphine | Probably 50% reduction Peak morphine effect is 90 min (half of peak effect at 5 min) | Long effect site equilibration time translates into a very slow reduction in the effect on termination of the infusion (4 h for 50% reduction) | Metabolite morphine-6 glucuronide buildup requires prolonged morphine use, but its renal excretion makes it very long lasting |
Fentanyl | 50% reduction | 50% reduction | Increased brain sensitivity Minimal change in pharmacokinetics Delayed absorption from fentanyl patch |
Alfentanil | 50% reduction | 50% reduction | Probably increased brain sensitivity |
Sufentanil | 50% reduction | 50% reduction | Minimal changes in pharmacokinetics |
Remifentanil | 50% reduction | 50% reduction | Slower bloodbrain equilibration, suggesting slower onset and offset Modest decreased Vcen |
Meperidine | Used only for postoperative shivering | Do not use | Toxic metabolite normeperidine whose renal excretion decreases with age |
Vecuronium | Slower onset | Slower recovery | Slightly greater liver metabolism than renal metabolism Older age nearly doubles metabolic half-time |
Cisatracurium | Slower onset | No significant changes with age | Mostly Hoffmann elimination Modest prolongation of metabolic half-time |
Rocuronium | Minimally slower onset | Liver metabolism slightly greater than renal metabolism Modest increase in metabolic half-time | |
Succinylcholine | Slower onset | Decreased Vcen | |
Edrophonium | Similar dosing and onset | Primarily renal elimination Modest increase in metabolic half-time | |
Neostigmine | Despite pharmacokinetic changes, some studies indicate the need for an increased dose with age | Decreased Vcen
Hepatic elimination Modest increase in metabolic half-time |
Vcen = central volume of distribution or initial volume of distribution; a smaller Vcen increases initial plasma levels and enhances transfer of drug in the target organ (brain, muscle).