Pharmacodynamics elderly

Geriatric factors a variety of factors, both pharmacokinetic and pharmacodynamic, that contribute to variable dmg responses in the elderly. These responses are not seen for every class of dmg. Thus, the depressant effects of the glycosides also appear to increase with aging (116,117). 

Vigilance for drug-drug interactions is required because of the greater number of medications prescribed to elderly patients and enhanced sensitivity to adverse effects. Pharmacokinetic interactions include metabolic enzyme induction or inhibition and protein binding displacement interactions (e.g., divalproex and warfarin). Pharmacodynamic interactions include additive sedation and cognitive toxicity, which increases risk of falls and other impairments. 

Within the medical community it has been acknowledged that elderly patients often respond to drug therapy differently from their younger counterparts. Aside from alteration of various pharmacokinetic and pharmacodynamic processes, elderly patients tend to suffer from a number of chronic conditions and, thus, have more complex dosage regimens. Additionally, a variety of physical limitations prevalent among the elderly may hinder their ability to self-administer medication. 

J. Roberts and N. Turner, Pharmacodynamic basis for altered drug action in the elderly, Clin. Geriatr. Med., 4, 127 (1988). 

The pharmacodynamics are affected due to altered levels of neurotransmitters and receptors in the central nervous system with age. The blood-brain barrier may be less effective, hence the brain may be exposed to higher drug and toxin levels in elderly subjects (Toornvliet et al. 2006). 

Tumheim K (2003) When drug therapy gets old pharmacokinetics and pharmacodynamics in the elderly. Exp Gerontol 38(8) 843-853... 

Sonne J, Loft S, Dossing M et al. (1991) Single dose pharmacokinetics and pharmacodynamics of oral oxazepam in very elderly institutionalised subjects. Br J Chn Pharmacol 31(6) 719-722 Taylor S, McCracken CF, Wilson KC et al. (1998) Extent and appropriateness of benzodiazepine use. Results from an elderly urban community. Br J Psychiatry 173 433—438... 

Injection Consider a dose of 5 mg per injection for elderly patients or when other clinical factors warrant. Consider a lower dose of 2.5 mg per injection for patients who otherwise might be debilitated, be predisposed to hypotensive reactions, or be more pharmacodynamically sensitive to olanzapine. 

Hammerlein A, Derendorf H, Lowenthal DT. Pharmacokinetic and pharmacodynamic changes in the elderly. Clinical implications. Clin Pharmacokinet 1998 35(l) 49-64. 

In many instances, drug sensitivity (pharmacodynamics) is altered in the elderly (Table 3). This may be a result of altered receptor numbers, post-receptor changes, alteration in membrane channel behaviour or in homeostatic counter-regulation. For example, /3-adrenoceptor sensitivity appears decreased with... 

Oberbauer R, Krivanek P, Turnheim K. Pharmacokinetics and pharmacodynamics of the diuretic bumetanide in the elderly. Clin Pharmacol Ther 1995 57(1) 42-51. 

Turnheim K, Krivanek P, Oberbauer R. Pharmacokinetics and pharmacodynamics of allopurinol in elderly and young subjects. Br 1 Clin Pharmacol 199948 501-509. 

In a report of 122 elderly patients on risperidone, hypotension was noted in 28.7% and symptomatic orthostatic hypotension was noted in 9.8%. Significant decreases in blood pressure occurred with risperidone treatment (p = 0.0001) and were common in patients with cardiovascular disease and those taking an SSRI or valproate (p = 0.03) (502). Hence, like other antipsychotics, risperidone should be prescribed cautiously for elderly patients and those with preexisting cardiac disease. Its hypotensive versus its orthostatic hypotensive effects may be an age-related pharmacodynamic response. Blood pressure, including orthostatic blood pressure, should be monitored routinely until the risperidone dosage is stabilized. Furthermore, when risperidone therapy is initiated in the elderly, dosage should be titrated from 0.25 to 0.5 mg two times a day with increments of 0.25 to 0.5 mg weekly (92). 

Finally, a good personal drug history often reveals that iatrogenic polypharmacy contributes to ill health, both physical and psychiatric, in elderly patients. Pharmacokinetic and Pharmacodynamic Issues... 

Mangoni AA Cardiovascular drug therapy in elderly patients Specific age-related pharmacokinetic, pharmacodynamic and therapeutic considerations. Drugs Aging 2005 22 913. [PMID 16323970]... 

---