Drug therapy: drug disposition in old age

The epidemiology of serious adverse drug reactions among the elderly

Although the incidence and prevalence of serious adverse drug reactions (ADRs) in the elderly cannot be accurately stated, published estimates appear to be unchanged since the earliest reports in the 1960s. Whereas heightened awareness of the problem may weigh in favour of a reduction in ADR frequency, the dramatic increase in the number and availability of therapeutic agents has undoubtedly contributed to the observed high proportion of drug-induced morbidity among acute geriatric hospital admissions. No single drug or drug class is of particular concern since none appears to cause serious morbidity out of proportion with its use. Although numerous studies have sought to identify risk factors for ADRs, the only truly independent predictor is the absolute number of concurrently used medications. However, other studies indicate that there is poor doctor-patient agreement regarding a patient's drug regimen, and interventions that aim to reduce the incidence of ADRs have failed to demonstrate a positive effect. Thus at present the most rational approach would appear to be to establish an accurate knowledge of the patients drug regimens: once this is known one can attempt to rationally minimise the number of medications without compromising therapeutic goals.

Drug therapy and the older person: role of the pharmacist

Older people in the UK receive a disproportionate amount of medication. They comprise 18% of the population but receive 45% of all prescription items. Not surprisingly they experience drug-related illnesses - in 1980, 1 in 10 admissions to acute geriatric units were wholly or partly due to adverse drug reactions. Drugs which should be used with particular care or even avoided in older people include benzodiazepines, warfarin, digoxin, aminoglycosides, tricylic antidepressants, antipsychotics and long-acting oral hypoglycaemic agents. Pharmacists can promote safer prescribing practices by advising both patients and doctors. The community pharmacist can assist in drug compliance by providing patients with additional information about individual drugs, identifying potential adverse drug reactions and interactions, supplying appropriate drug containers or compliance aids, and even arranging home visits for patients unable to visit the pharmacist. Some community pharmacists provide pharmaceutical advice and services to residential and nursing homes. Pharmacists' advice to doctors can include one to one discussions in either primary or secondary care, assisting in medication review, providing information to prescribing committees, compiling drug formularies, assisting in auditing of prescribing practices and organising disposal of unwanted medicines and poisons campaigns.

Cancer chemotherapy in the elderly

As the geriatric population is growing, it is increasingly important to be familiar with chemotherapy for the elderly. Age-related changes in pharmacokinetics are documented for doxorubicin, etoposide, ifosfamide, daunorubicin, mitomycin, cisplatin and methotrexate. The hematological toxicity of most standard-dose chemotherapy is not affected by age in patients with normal organic functions and good performance status, although increased toxicity with aging is suggested in the use of actinomycin-D, etoposide, vinblastin, methotrexate, methyl-CCNU, doxorubicin and mitomycin, and in dose-intensive chemotherapy. Among non-hematological toxicities, only doxorubicin-induced cardiomyopathy and bleomycin-induced pulmonary toxicity are demonstrated to be accelerated in the elderly. There is no evidence that advanced age decreases the efficacy of chemotherapy for tumors, except for Hodgkin's disease and acute leukemia. These results suggest that advanced chronological age alone is not always associated with severe toxicity and poor prognosis, and that many elderly patients with cancer will benefit from chemotherapy. To answer questions regarding the optimal chemotherapy regimen, dose and intensity in this population, the influence of age should be analyzed in a multivariate approach in future studies.

Pharmacokinetics and pharmacodynamics of diphenhydramine 25 mg in young and elderly volunteers

Thirty-seven young and elderly male and female volunteers 21 to 76 years of age received a single 25-mg oral dose of diphenhydramine or matching placebo in a double-blind, randomized, two-way crossover study. Plasma diphenhydramine concentrations, self-ratings of sedation, mood, and autonomic effects, performance on the digit-symbol substitution test (DSST), and heart rate were determined for 24 hours after administration. Information acquisition and recall were tested at 2.5 and 24 hours after administration. Age and gender did not significantly influence diphenhydramine peak plasma concentration, time of peak concentration, elimination half-life, area under the plasma concentration curve, or apparent oral clearance. Effects on psychomotor performance, sedation, mood, and memory did not differ between diphenhydramine and placebo in either group. Thus, the pharmacokinetics of single 25-mg oral doses of diphenhydramine are not influenced by age or gender. This dose of diphenhydramine produces essentially undetectable pharmacodynamic effects in both the young and elderly.

Antidepressant drugs in the elderly

1. In this article some of the most important and tolerated drugs in the elderly are reviewed. 2. Tricyclic antidepressants have to be used carefully because of their important side effects. Nortriptyline and desipramine appear to be the best tolerated tricyclics in old people. 3. Second generation antidepressants are preferred for the elderly and those patients with heart disease as they have milder side effects and are less toxic in overdose. 4. MAO inhibitors are useful drugs in resistant forms of depression in which the above mentioned drugs have no efficacy and the last generation drugs (reversible MAO inhibitors), such as moclobemide, seem to be very successful. 5. Lithium is sometimes used especially to prevent recurrence of depression, even if its use is limited in old patients due to its side effects. 6. Psychotherapy is often used as an adjunct to pharmacotherapy, while electroconvulsant therapy is used only in the elderly patients with severe depression, high risk of suicide, or drug-resistant forms.

The effects of age and gender on the single dose pharmacokinetics of avitriptan administered to healthy volunteers

The effects of age and gender on the single dose pharmacokinetics of avitriptan and its three metabolites were assessed in 15 young men, 15 young women, 15 elderly men and 15 elderly women. Avitriptan was administered as a 150-mg capsule after a 10-hour fast and serial plasma and urine samples were collected up to 36 hours after the dose. Plasma samples were analyzed for avitriptan and its metabolites, N-desmethyl avitriptan (ND048), O-desmethyl avitriptan (OD048), and methoxypyrimidinyl piperazine (MPP). Urine samples were analyzed for only avitriptan and MPP. Avitriptan was well tolerated in all four groups. The drug was rapidly absorbed with a median time to maximum plasma concentration (tmax) between 0.5 and 1.5 hours. No significant gender-related differences were found in the maximum plasma concentration (Cmax) and area under the concentration-time curve extrapolated to infinity (AUC0-infinity) of avitriptan. Renal clearance of avitriptan was significantly smaller in young women compared with young men, but this is clinically not relevant because only 2% to 3% of the total dose is excreted unchanged. Compared with the young volunteers, mean Cmax was approximately 50% higher in the elderly but there was no difference in the AUC0-infinity between the 2 age groups. Plasma concentrations of ND048, OD048, and MPP were each 50 to 100 fold lower than those of avitriptan. Hence some age- and gender-related differences found in the pharmacokinetics of avitriptan metabolites are probably not relevant in the assessment of overall safety and efficacy of avitriptan. Based on the pharmacokinetics and tolerability, no age or gender-related dose adjustment is necessary for avitriptan.

Effect of aging on mixed-function oxidation and conjugation by isolated perfused rat livers

Aging is known to decrease hepatic cytochrome P450 content in rats. However, limited information is available on the effects of aging on mixed-function oxidation and conjugation in intact liver. The purpose of these studies was to determine the effects of aging on oxidation and conjugation of p-nitrophenol (pNP) in perfused livers from male Sprague-Dawley rats. Livers from senescent (22-24 months) or young adult (3-6 months) rats were perfused in a nonrecirculating hemoglobin-free system and supplemented with pNP (60 microM). Glucuronide and sulfate conjugates of the oxidation product, 4-nitrocatechol, in effluent perfusate were cleaved enzymatically and 4-nitrocatechol was determined colorimetrically. Rates of 4-nitrocatechol production were decreased in senescent compared with young adult rats (0.67 +/- 0.14 vs 0.92 +/- 0.15 micromol/g/hr). However, the rates of oxidation of pNP in microsomes from senescent rats were similar to those in young adult rats. Hepatic malate content was decreased approximately 50% in livers from senescent compared with young adult rats in the presence and absence of pNP, suggesting that movement of reducing equivalents from the mitochondria to the cytosol, and thus cytosolic NADPH supply, may have been diminished by senescence. The rates of conjugation of 60 microM pNP in perfused livers from senescent rats were similar to those in young adult rats, but Km and Vmax values of microsomal 4-nitrocatechol glucuronyltransferase were about 2.5- and 1.6-fold higher, respectively, in livers from senescent compared with young adult rats. Hepatic glycogen content was about 50% lower in livers from senescent compared with young adult rats, but the contents of UDP-glucose and UDP glucuronic acid were similar between the two groups. Taken together, the data are consistent with the hypothesis that rates of mixed-function oxidation are decreased in intact livers from senescent compared with young adult rats, due possibly to age-related changes in cofactor supplies. Glucuronidation of low, but not high, concentrations of substrates may be affected by age-related changes in Km and Vmax values of microsomal glucuronyltransferase.

Absence of age and gender effects on the pharmacokinetics of a single 500-milligram oral dose of levofloxacin in healthy subjects

The influence of age and gender on the pharmacokinetics of levofloxacin in healthy subjects receiving a single oral 500-mg dose of levofloxacin was investigated in this parallel design study. Six young males (aged 18 to 40 years), six elderly males (aged > or = 65 years), six young females (aged 18 to 40 years), and six elderly females (aged > or = 65 years) were enrolled and completed the study. The study reveals that the bioavailability (rate and extent) of levofloxacin was not affected by either age or gender. In both age (young and elderly) and gender (male and female) groups of subjects, peak concentrations in plasma were reached at approximately 1.5 h after dosing; renal clearance of levofloxacin accounted for approximately 77% of total body clearance, and approximately 76% of the administered dose was recovered unchanged in urine over the 36 h of collection. The apparent differences in the calculated pharmacokinetic parameters for levofloxacin between the age groups (young versus elderly) and between the gender groups (males versus females) could be explained by differences in renal function among the subjects. A single dose of 500 mg of levofloxacin administered orally to both young and old, male and female healthy subjects was found to be safe and well tolerated. As the differences in levofloxacin kinetics between the young and the elderly or the males and the females are limited and are mainly related to the renal function of the subjects, dose adjustment based on age or gender alone is not necessary.

The effects of antidepressants on psychomotor function with particular reference to reboxetine

This review assesses the relative efficacy and side-effect profile of the currently available treatment options for major depression and the new selective noradrenergic agent, reboxetine. The effects of these treatments on psychomotor function are reviewed using: choice reaction time (CRT) and critical flicker fusion threshold (CFFT) measurements to compare and contrast the various antidepressants. Tricyclic antidepressant (TCA) agents are associated with an increased risk of accidents, especially in the elderly (primarily accidents related to driving or falls/fractures due to postural hypotension). In comparison, the newer noradrenergic agents such as reboxetine have demonstrated significant improvements in the incidence and severity of effects on psychomotor function. Such a lack of side-effects makes agents like reboxetine most useful for the treatment of depression in ambulant patients performing their usual activities of daily living.

Age might influence the frequency distribution of metoprolol hydroxylation polymorphism in a Chinese population

The frequency distribution of the 8-hour urinary ratio of metoprolol/alpha-hydroxymetoprolol (MR) was investigated in 206 healthy rural Chinese volunteers. The frequency of the poor metabolizer phenotype of metoprolol alpha-hydroxylation was 0% in this Chinese population. When the 206 subjects were subgrouped into four groups by age, the excretion of alpha-hydroxymetoprolol was significantly lower in the subjects with age older than 41 years compared to two younger groups (16-30 years), and the metoprolol hydroxylation metabolic ratio(metoprolol/a-hydroxymetoprolol, MR) was higher in these middle-aged subjects, indicating that age may affect the frequency distribution of the 8-hour urinary MR or log MR, although multiple regression analysis did not show a significant correlation between age, urine volume and MR. Also, a significant correlation was found between age and the excretion (percentage of dose) of alpha-hydroxymetoprolol in 8-hour urine (r = 0.259, P < 0.001). On the other hand, both multiple regression analysis and nonparametric tests showed that the larger the amount of urine excreted, the more metoprolol was recovered, demonstrating that the urinary excretion of unchanged metoprolol is renal flow-limited.

Anticonvulsant therapy in aged patients. Clinical pharmacokinetic considerations

Alterations in drug disposition that occur with aging are now becoming widely recognised, and there is an increasing number of drugs for which the approach to therapy in elderly patients can be based on pharmacokinetic data. Both healthy aging and comorbid disease can alter the responsiveness of the body to drugs and to their absorption, distribution and elimination. Altered absorption in the elderly has not been documented after oral ingestion of any anticonvulsant drug. Increased adipose tissue in the elderly may raise the apparent volume of distribution (Vd) of lipid-soluble drugs. An increased Vd in the elderly has been shown for diazepam and clobazam, but not midazolam. The data are inconclusive for phenytoin and valproic acid (sodium valproate). The decreased plasma protein binding that often occurs in the elderly has few clinical consequences. The reduced liver function that to occur with aging seems to affect the elimination of drugs that are mainly cleared by oxidative metabolism [e.g. carbamazepine, phenytoin and phenobarbital (phenobarbitone)]. Reduced clearances for methylphenobarbital (methylphenobarbitone), diazepam, midazolam and clobazam occur in elderly men, but not in women. The reduced renal function that is seen in old age affects the disposition of drugs that are eliminated mainly by direct renal excretion. Thus. the clearances of vigabatrin and gabapentin correlate with creatinine clearance. Such considerations may help guide anticonvulsant dosage in the elderly.

Music increases satisfaction in elderly outpatients undergoing cataract surgery

PURPOSE

Music has long been known to reduce anxiety, minimize the need for sedatives, and make patients feel more at ease. The purpose of the study was to evaluate the effect of music in elderly outpatients undergoing elective cataract surgery with retrobulbar block and monitored anaesthetic care using fentanyl or alfentanil and midazolam.

METHODS

One hundred and twenty one patients were prospectively and randomly assigned to hear: relaxing suggestions, white noise, operating room noise or relaxing music via audio-cassette headphones. Vital signs were documented before and after retrobulbar block and every 15 min thereafter. Anxiety was assessed using the State-Trait Anxiety Inventory (STAI) before and after surgery. Visual analogue scales (VAS) were used to assess anxiety and patient satisfaction postoperatively with a standardized questionnaire. Between group comparisons were made using Chi-Square, or ANOVA, where appropriate.

RESULTS

There were no differences between groups in STAI or anxiety VAS scores at any time. Differences were noted in systolic blood pressure, but not in other vital signs. Patients' ratings of the whole operative experience, satisfaction with the tape played, general level of relaxation and preference for the chosen tape for subsequent surgery were different (music > relaxing suggestions > white noise and OR noise, P < 0.05).

CONCLUSIONS

Elderly patients undergoing cataract surgery under retrobulbar block were more satisfied with their experience if they heard relaxing music, rather than relaxing suggestions or white noise or OR noise. The type of auditory stimuli to which the patients were exposed did not influence the level of anxiety.

Gradual withdrawal from benzodiazepines in residents of homes for the elderly: experience and suggestions for future research

OBJECTIVE

A randomised, controlled clinical trial was performed to study the long-term effect of gradual withdrawal from benzodiazepines on the daily functioning of residents of homes for the elderly. The planned sample size was not achieved due to recruitment and follow-up problems.

RESULTS

The results in this small sample nevertheless suggest that gradual withdrawal from benzodiazepines is possible in residents of homes for the elderly, and that it can have a positive effect on their daily functioning. No major withdrawal symptoms were observed, although there was a decrease in sleep quality during withdrawal.

CONCLUSION

The findings are promising for further research, but researchers should anticipate the problems inherent in executing a trial with institutionalised elderly subjects.

Management of epilepsy in the elderly

Epilepsy in elderly patients is a growing worldwide challenge; as the population ages, the prevalence of epilepsy increases. Management of epilepsy in elderly patients requires an understanding of their unique medical and pharmacologic characteristics. Accurate assessment of seizures, thorough neurologic assessment to define etiology, and evaluation of concomitant illnesses and living situations are necessary for comprehensive treatment planning and informed management. Expect elderly patients to present challenges to treatment that include concomitant diseases, obligatory polypharmacy with accompanying drug interactions, and age-related changes in renal and hepatic physiology that alter drug metabolism and elimination. Elderly patients have declining intellectual function, motor impairment, or altered special sensory function that make them susceptible to dose-related CNS side effects of antiepileptic drugs (AEDs). When AEDs are added to the medical regimen of an elderly patient, the physician must review all prescribed drugs. Drugs prescribed for concomitant illnesses such as behavioral problems, cardiovascular disease, hypertension, and infection may alter the distribution and metabolism of AEDs, with an impact on efficacy and occurrence of adverse effects. AEDs tend to induce metabolism of other drugs, leading to a decline in target response. Optimal care of elderly patients with epilepsy includes use of free levels to monitor AED concentrations, careful dose selection, and physician sensitivity to patients' social problems.

Clinical trials in the elderly. Should we do more?

Much of the information on which treatment decisions are based in elderly patients is derived from studies involving younger adults. The benefit to risk ratio of any given intervention may be quite different in frail older patients with significant comorbidities, and the applicability of such study findings to routine geriatric medical practice is therefore limited. The recruitment of significant numbers of elderly patients into trials is necessary to enable clinicians to make informed and rational therapeutic decisions in this expanding population.

Age dependence of the cardiac lesions induced by minoxidil in the rat

To evaluate the age- and dose-dependence of the cardiotoxicity induced by minoxidil, histologic studies were made of the hearts of 3-, 6-, 15- and 24-month-old Sprague Dawley rats treated with either 10, 50 or 250 mg/kg of the drug p.o. daily for two consecutive days. The 10 mg/kg dose of minoxidil induced myocyte necrosis in each of the 24-month-old rats but only in one other animal (6-month-old). The 50 mg/kg dose produced necrosis in all the 15- and 24-month-old rats, but in only one of the other animals (6-month-old), while the 250 mg/kg dose induced necrosis in animals of all ages. Inflammation was present in all minoxidil-treated animals, but at each dose level it was most severe in the oldest rats. Interstitial hemorrhages were observed at all dose levels, but increased in frequency and severity with the dose of minoxidil, and at each dose level they were more severe in the oldest animals. Vascular lesions consisting of arteriolar damage and calcification were observed only in the 24-month-old animals. Thus, these data demonstrate that the cardiac lesions induced by minoxidil are more frequent and severe in older than in younger rats.

Effectiveness and safety of low-dose pravastatin and squalene, alone and in combination, in elderly patients with hypercholesterolemia

A double-blind, placebo-controlled study was conducted to compare the efficacy and safety of low-dose (10 mg) prevastatin and squalene (860 mg), either alone or in combination therapy, with placebo in the treatment of elderly patients with hypercholesterolemia. Ambulatory elderly patients (N = 102) were assigned in randomized fashion to receive active treatment or placebo for 20 weeks after a single-blind placebo lead-in period of 8 weeks. Total cholesterol and triglyceride levels in plasma were at least 250 mg/dL and less than 300 mg/dL, respectively. Concentrations of lipids and lipoproteins were measured, and clinical laboratory tests included liver function and creatine kinase determinations. Pravastatin 10 mg daily was more effective than squalene in reducing total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides and in increasing levels of high-density lipoprotein (HDL) cholesterol. Combination therapy significantly reduced total cholesterol and LDL cholesterol and increased HDL cholesterol to a greater extent than either drug alone. Adverse events and clinical laboratory abnormalities were generally mild and transient in all groups, and all but two patients finished the study. The incidence of side effects was low; myopathy did not occur. Coadministration of pravastatin and squalene combined the specific effects of the two drugs on lipoprotein concentrations. This combination may be useful and more cost-effective in elderly patients with hypercholesterolemia, who might have a higher incidence of side effects when using larger doses of pravastatin alone.

Pharmacokinetics and pharmacodynamics of glyburide in young and elderly patients with non-insulin-dependent diabetes mellitus

OBJECTIVE

To determine the influence of age on the pharmacokinetics and pharmacodynamics of glyburide after acute and chronic dosing in young and elderly subjects with non-insulin-dependent diabetes mellitus.

DESIGN

Ten elderly (mean age 69.3 +/- 3.1 y) and 10 younger (mean age 45.6 +/- 4.5 y) patients received a glucose challenge test at baseline, with a 2.5-mg dose of glyburide at week 0 (acute dose) and again at weeks 6 and 12 of chronic glyburide therapy. Glyburide doses were titrated to a maximum daily dosage of 20 mg to achieve a glucose concentration of 7.8 mmol/L or less. During 24-h pharmacokinetic determinations at weeks 0, 6, and 12, serial blood samples were obtained for glyburide determination with HPLC. Serial blood samples for glucose, insulin, and C-peptide determinations were obtained at baseline (week -1) and at weeks 0, 6, and 12.

RESULTS

All pharmacokinetic parameters assessed for glyburide were statistically comparable between the two age groups with the exception of a shorter time to peak concentration in the elderly at weeks 0 and 12. The glucose pharmacodynamic response to glyburide was not statistically different between the two groups. However, there was a statistically significant greater C-peptide response in the elderly group at all evaluation weeks.

CONCLUSIONS

Aging appears to have no influence on the pharmacokinetics of glyburide. Observed pharmacodynamic differences indicate the necessity for dosage titration to a specified therapeutic response regardless of patient age.

Effect of age and gender on pharmacokinetics of atorvastatin in humans

Atorvastatin is a new 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor that reduces plasma cholesterol by inhibiting cholesterol synthesis and increasing cellular uptake of low density lipoproteins. The effects of age and gender on the pharmacokinetics of atorvastatin after administration of single 20-mg tablets of atorvastatin were studied in 16 young and 16 elderly volunteers (8 men and 8 women in each age group). Plasma equivalent concentrations of atorvastatin were quantitated by a validated enzyme inhibition bioassay. Atorvastatin was well tolerated by the participants. The equivalent maximum concentration (Cmax) of atorvastatin was 42.5% higher in elderly participants (age, 66-92 years) than in young participants (age, 19-35 years) and 17.6% higher in women than in men. In addition, mean area under the concentration-time curve (AUC0-infinity) and half-life (t1/2) were 27.3% greater and 36.2% longer, respectively, in elderly adults than in young adults and 11.3% lower and 19.9% shorter, respectively, in women than in men. Because the primary site of action for HMG-CoA reductase inhibitors is the liver and atorvastatin is subject to extensive first-pass hepatic metabolism, it is unclear whether these age- and gender-related differences in the pharmacokinetics of atorvastatin will be clinically important. Results of subsequent safety and efficacy trials should help clarify the clinical significance of these pharmacokinetic differences.

Neostigmine reversal of vecuronium neuromuscular block and the influence of renal failure

The duration of clinical relaxation induced by vecuronium and reversal by neostigmine was studied in 40 patients with renal failure (RF) and 40 patients with normal renal function (NL) under general anesthesia. Patients were premedicated with flunitrazepam, and anesthesia commenced with fentanyl 1-2 micrograms/kg, thiopental 5-8 mg/kg, and vecuronium 0.1 mg/kg. Anesthesia was maintained with 60% nitrous oxide in oxygen, isoflurane 0.3%-1.0% end-tidal concentration, and 1 microgram/kg fentanyl every 20-30 min. Neuromuscular block was reversed by the administration of intravenous neostigmine 40 mg/kg at the time of reappearance of either two or four responses to the train-of-four (TOF) stimulation. Monitoring of neuromuscular function consisted of supramaximal TOF stimulation of the ulnar nerve and the evoked thumb response was registered using a force transducer. Spontaneous recovery time, reversal time, and the time to recovery of TOF ratio to 0.7 were recorded. RF did not prolong the vecuronium neuromuscular blocking effect, reversal was achieved at the same rate in NL as in RF, and the duration of reversal of neuromuscular blocking effect of vecuronium was not influenced by the time of administration of neostigmine. Therefore, the neuromuscular blocking effect of a tracheal intubating dose of vecuronium can be reversed at the same rate in patients with end-stage RF as in patients with normal kidney function.

Influence of age, renal and liver impairment on the pharmacokinetics of risperidone in man

The pharmacokinetics of the antipsychotic agent risperidone were investigated in healthy young and elderly subjects, cirrhotic patients and patients with moderate and severe renal insufficiency. In a comparative trial, a single oral 1-mg dose was administered to fasting subjects. Plasma and urine concentrations of the parent compound risperidone and the active moiety (i.e. risperidone plus 9-hydroxy-risperidone) were measured by radioimmunoassays. No or only small changes in plasma protein binding were observed in hepatic and renal disease, whereas the protein binding was not influenced by aging. The inter-individual variability in plasma concentrations of the active moiety was much less than the variability in plasma concentrations of risperidone. Three out of six subjects, behaving like poor metabolizers, were on medication (thiethylperazine, amitriptyline, metoprolol) that may inhibit risperidone metabolism by CYP2D6 (debrisoquine 4-hydroxylase). The pharmacokinetics of risperidone in elderly and cirrhotic patients were comparable to those in young subjects, whereas total oral clearance was reduced in renal disease patients. The elimination rate and clearance of 9-hydroxy-risperidone was reduced in elderly and renal disease patients because of a diminished creatinine clearance. The CL(oral) of the active moiety, which is primarily 9-hydroxy-risperidone, was reduced by about 30% in the elderly and by about 50% in renal disease patients. In addition, the t1/2 of the active moiety was prolonged (19 h in young subjects versus about 25 h in elderly and renal disease patients). Based upon the pharmacokinetics of the active moiety, a dose reduction and a cautious dose titration is advised in the elderly and in patients with renal disease. In cirrhotic patients, the single-dose pharmacokinetics were comparable to those in healthy young subjects.

Interactions between alcohol and other drugs

More than 75% of people age 65 and older use medications. Of the drugs most commonly used by older people, many have potential to interact adversely with alcohol. The absorption, distribution, metabolism, and effects of drugs or alcohol may be affected. The major adverse clinical outcomes of drug-alcohol interactions are altered blood levels of the medication or of alcohol, liver toxicity, gastrointestinal inflammation and bleeding, sedation and delirium, disulfiram-like reactions, and interference with the desired effect of medications. Since alcohol is commonly used by elderly people, educating patients about the potential for these interactions should be a routine part of health care visits.

Aging alters the pharmacokinetics of pyridostigmine

The duration of the antagonism to neuromuscular blockade produced by pyridostigmine is prolonged in elderly patients, and a pharmacokinetic explanation was sought. Ten elderly (71-85 yr) and 10 younger (21-51 yr) patients were anesthetized with thiopental, nitrous oxide, and isoflurane and paralyzed with a combination of d-tubocurarine and pancuronium. When twitch height returned to 5% of baseline, pyridostigmine 0.25 mg/kg was administered and blood samples were collected intermittently for 6 h. Pyridostigmine plasma concentrations were determined by radioimmunoassay and after an hour were always greater in the elderly than in the younger patients. In both groups, plasma pyridostigmine decrement curves were best described by triexponential equations. Pharmacokinetic analysis revealed that plasma clearance in the elderly group was significantly decreased compared to that in the younger group (6.7 +/- 2.2 vs 9.5 +/- 2.7 mL.kg-1.min-1, P < 0.05). Elimination half-lives and volumes of distribution were not significantly different between groups. We conclude that a possible explanation for the prolonged duration of action of pyridostigmine in the elderly is its slow plasma clearance.

Effects of aging on antipyrine clearance: predictive factors of metabolizing capacity

The purpose of this study was to identify variables that can account for the decline of antipyrine clearance (CLAP) in elderly adults and that may help predict a reduction in metabolizing capacity. For comparison, ClAP was determined in 177 elderly (mean age 82 years) and 25 young (mean age 29 years) volunteers. Antipyrine (1 g) was administered orally and ClAP was determined by the one-sample saliva method. Mean ClAP was reduced by 38% and antipyrine half-life increased by 64% in old subjects. Multiple regression analysis of ClAP revealed an independent value for age, serum aspartate transaminase (AST), and height in the elderly. The independent variables collectively accounted for 27% of the variance explained. Age, high serum AST, use of diuretics, and no consumption of drugs known to stimulate oxidative metabolism were selected by multivariate analysis (logistic model) as independent predictors of a low metabolizing capacity. The findings indicate that factors other than age may contribute to impaired hepatic oxidative metabolism in the elderly.

High-risk drugs in the elderly population

Drug therapy in elderly patients is affected by age-related changes in distribution and elimination and is further complicated by the increased sensitivity aged persons have to many of the effects of medications. Medications are often necessary in the elderly population, but care should be made to properly monitor these patients, especially those taking multiple drugs. Nurses, who are at the front lines of health care in all areas of practice, should be aware of drugs that may be high risk for use in the elderly and monitor these patients carefully for signs and symptoms of toxicity.

Recent advances in geriatric psychopharmacology

Psychopharmacotherapy of the elderly must take into account the effects of age-related changes in the structure and function of the brain and various organs. In general, older people are more sensitive than young people to both the therapeutic and toxic effects of psychotropic medications, necessitating lower doses and longer dosage intervals. This holds true for the treatment of 5 major types of psychiatric illness (depression, bipolar disorder, anxiety, psychotic disorders and dementia). The tricyclic antidepressants, although efficacious, inexpensive, and backed by 30 years of experience, are less well tolerated by the elderly than are newer antidepressants such as the selective serotonin uptake inhibitors. Problems with monoamine oxidase (MAO) inhibitors, including orthostatic hypotension and restrictions in diet and other medication use, have been overcome by the advent of reversible selective inhibitors of MAO-A, but the efficacy of these in the elderly has yet to be proven in clinical trials. Lithium remains the mainstay for the treatment of bipolar disorder. However, careful dosing and monitoring of plasma lithium concentrations are required in the elderly due to changes in pharmacokinetics and pharmacodynamics which make older patients very sensitive to the toxic effects of this medication. Similarly, age-related changes in the pharmacokinetics and pharmacodynamics of the benzodiazepines, the most frequently prescribed medications for anxiety in the elderly, result in recommendations for lower doses and preferential use of those agents metabolised by conjugation (e.g. oxazepam). Buspirone, a partial serotonin 5-HT1A-agonist which is better tolerated than benzodiazepines in the elderly, may be used as an alternative. The elderly are extremely sensitive to extrapyramidal adverse effects which the typical antipsychotics (neuroleptics) exhibit to varying extents. The selection of a suitable agent for the treatment of a psychotic disorder should be based upon the adverse effect profile of the drug and the specific symptoms and situation of the patient. The newer atypical antipsychotics, clozapine and risperidone, have yet to be well-studied in the elderly. Dementia, exemplified by Alzheimer's disease, is almost exclusively an illness of the elderly. Only one medication, tacrine, has been approved for its treatment, based on extensive basic research and positive results of several clinical trials. Its long-term benefits have yet to be determined and it has several adverse effects, including a tendency to increase liver enzymes to the extent that the medication has to be discontinued.(ABSTRACT TRUNCATED AT 400 WORDS)

Osteoarthritis in older patients. Optimum treatment

A number of therapeutic options to control pain, maintain function and decrease disability are available for older patients with osteoarthritis. The indication for pharmacological therapy should be restricted to periods with pain. Great attention should be given to nonpharmacological interventions such as education, exercise, lifestyle modification and emotional support. If medication is necessary, most patients require only pure analgesics such as paracetamol (acetaminophen); nonsteroidal anti-inflammatory drugs (NSAIDs) should be used if patients do not respond to simpler measures. All medication should be carefully monitored considering the frequency of adverse drug reactions in older patients.

Age but not gender selectively affects expression of individual cytochrome P450 proteins in human liver

Multivariate linear regression analysis was used to examine the influence of age, gender and environmental variables on the hepatic content of cytochromes P450 (CYP, P450) 1A2, 2C, 2E1 and 3A in 71 subjects; 21 with histologically normal livers and 50 with chronic liver disease. There was a clear negative association between age and total P450 content, NADPH-cytochrome c reductase activity and levels of 2E1 and 3A proteins. 1A2 and 2C proteins were unaltered with advancing age. Gender did not influence the expression of any of the CYP proteins. Cigarette smoking was associated with enhanced levels of 1A2, but effects of drug ingestion and alcohol consumption were not apparent in this study, probably because of case selection. It is concluded that age but not gender is a constitutional factor that influences the hepatic content of cytochrome P450 and selected CYP proteins.

Effect of aging on atenolol pharmacokinetics and pharmacodynamics

A study was conducted to characterize and compare the pharmacodynamics and pharmacokinetics of atenolol in young and elderly men. Six young (mean +/- SD, 25.0 +/- 3.0 years) and six elderly (63.0 +/- 3.2 years) healthy men took atenolol 100 mg orally once daily for 6 days. Heart rate response to submaximal exercise was measured at selected times for 48 hours, and plasma and urine samples were collected over the same time interval. The Sigmoid Emax model was fit to percent reductions in exercise heart rate and atenolol plasma concentrations. The younger men had significantly lower values for area under the steady-state plasma concentration-time curve and higher values for systemic clearance/F and renal clearance. EC50 values showed a trend toward greater sensitivity to the negative chronotropic effects of atenolol among the elderly men. Model-derived percent reductions in heart rate were greater at all concentrations among the elderly men. These data suggest that group differences in atenolol pharmacokinetics were likely a result of age-related decline in renal function, and that the elderly subjects were at least as sensitive as, and maybe even more sensitive than, the younger subjects to the negative chronotropic effects of atenolol.

Drug therapy

Drug therapy for individuals of any age is difficult but prescribing for older patients offers special challenges. Older people take about three times as many prescription medications as younger individuals do, mainly because of their increased prevalence of chronic medical conditions. However, taking several drugs together substantially increases the risk of drug interactions, unwanted effects, and adverse reactions. Many medications need to be used with special caution because of age-related changes in pharmacokinetics and pharmacodynamics. For some drugs, an increase in the volume of distribution (eg, diazepam) or a reduction in drug clearance (eg, digoxin) may lead to higher plasma concentrations in older than in younger patients. Pharmacodynamic changes with ageing may result in an increased sensitivity to the effects of certain drugs (eg, opioids) for any given plasma concentration. While a physician can usually do little to alter the characteristics of individual older patients to affect the kinetics or dynamics of drugs, the decision whether to prescribe anything at all, the choice of drug, and the manner in which it is to be used (eg, dose and duration of therapy) are all factors that are under control of the prescriber. Patient adherence to the regimen prescribed is important, and there should be a partnership between physician and patient in therapeutic decision making. We will discuss here ways of improving prescribing for older patients. Specifically, we will examine the scarcity of information to guide prescribing decisions, the general principles of prudent prescribing, and the opportunities to clarify and expand knowledge about drug therapy in the elderly.

A practical guide to prescribing in nursing homes. Avoiding the pitfalls

The abundant use of drugs in nursing homes demands special attention. Inappropriate indications and dosages, and lack of monitoring of drug-related effects and adverse reactions in patients are problems which can easily be solved. Knowledge of basic aspects of geriatric pharmacokinetics, and of basic rules and the main pitfalls involved in prescribing drugs for the elderly is essential, and demands both training of personnel and a change in prevailing attitudes.

Treatment of infections in elderly patients

Infections are common in elderly persons. The clinical manifestations of infection may be atypical or absent in the elderly. The microbial cause for many common infections may be more diverse in elderly patients, and obtaining diagnostic clinical specimens often is more difficult. Aging is associated with changes in pharmacokinetics and a higher rate of adverse drug reactions. These factors impact on the approach to treating infections in the elderly.

The effect of age on pharmacokinetics of antiepileptic drugs

Management of epilepsy in the elderly requires understanding of the unique biochemical and pharmacologic characteristics of this patient population. Accurate assessment of seizures and identification of epilepsy syndromes, thorough neurologic assessment to define etiology, and comprehensive evaluation of the patient's health and living situation are necessary for informed management decisions. Challenges to treatment include concomitant diseases, polypharmacy with accompanying drug interactions, and changes in physiology, such as changes in renal clearance and hepatic function than alter drug absorption, protein binding, metabolism, and elimination. Elderly patients with declining intellectual function, motor impairment, or altered sensory function may be especially susceptible to dose-related CNS side effects of antiepileptic drugs (AEDs). Drugs prescribed for concomitant illnesses such as hypertension, cardiovascular disease, infections, behavioral problems, and gastrointestinal disturbances may alter absorption, distribution, and metabolism of AEDs, with an adverse impact on efficacy and increased occurrence of adverse effects. The AEDs may induce metabolism of other drugs, resulting in decline in target response. Addition of an AED to an elderly patient's medical regimen requires careful review of all prescribed drugs. Optimal care of elderly patients with epilepsy includes use of free drug levels to monitor AED concentrations, careful dose selection, and sensitivity to the social problems that may occur in this population.

Drug utilization in the old old and how it relates to self-perceived health and all-cause mortality: results from the Bronx Aging Study

OBJECTIVE

To characterize medication use in a "well" very old population and relate the quantity and type of medication use to 10-year mortality.

DESIGN AND SUBJECTS

A longitudinal, 10-year, follow-up study involving 488 healthy, community-dwelling volunteers aged 75 to 85 years. The subjects underwent a detailed baseline evaluation and annual assessments that included comprehensive physical exams, laboratory and diagnostic tests, and related interviews. Prescription and nonprescription drug use was determined by self report, confirmation through hospital records, and reports by subjects and significant others.

RESULTS

At study baseline, the mean number of prescription and nonprescription medications used was 2.3 and 1.5, respectively. Female subjects (n = 315), those older than 80 years, or those who reported themselves to be in fair or poor health on initial health self-report were found to show significantly increased use of prescription medications. The most commonly used classes of medications were cardiovascular drugs and analgesics. Subjects who were consuming a greater number of prescription and nonprescription medications did not have higher mortality rates. After correcting for differences in cardiovascular health status between users and nonusers, only digoxin approached significance as an independent predictor of death (P < .08).

CONCLUSION

This study confirmed that medication use in an ambulatory, old old population is not excessive. The oldest subjects in the cohort consumed more medications than did the younger subjects. Women used more prescription drugs than men. Increased medication use was associated with worse ratings on health self report. Medication use alone, however, was not a predictor of 10-year mortality in this population. Questions are raised about the inappropriate prescription of digoxin in older subjects.

The effect of age and liver disease on the pharmacokinetics of the calcium antagonist, nisoldipine

Two studies were performed-one in elderly, hypertensive patients and one in patients with chronic liver disease-to investigate the effect of age and liver disease upon the pharmacokinetics of nisoldipine, a dihydropyridine-type calcium antagonist. The effect of acute and chronic administration of nisoldipine (once and twice daily) was investigated in 17 elderly hypertensive patients. Compared with previously published data from young healthy volunteers, the values for Cmax and AUC appear to be higher in elderly hypertensive patients while Tmax and half-life were unchanged. Nisoldipine significantly reduced both systolic and diastolic blood pressure when given acutely to elderly hypertensive patients. Major alterations in the pharmacokinetics of nisoldipine were found in 7 patients with chronic liver disease when compared with the elderly hypertensives and healthy volunteers. The values for AUC, Cmax, half-life and volume of distribution were all higher than expected from the volunteer data while clearance was lower. One patient receiving primidone had very low nisoldipine levels, suggesting that the concomitant administration of agents that may induce the metabolism of nisoldipine should be discouraged. Nevertheless, comparisons of nisoldipine plasma levels after acute and chronic administration showed no evidence of any accumulation in either patient population in the doses used. The drug was generally well tolerated although 1 patient with chronic liver disease was withdrawn due to fluid retention.

The pharmacokinetics of zileuton in healthy young and elderly volunteers

The effects of age and gender on the single and multiple dose pharmacokinetics of zileuton have been examined in a phase I nonblinded study. A total of 27 healthy volunteers were evaluable, 9 in the young group (age range 20 to 40 years; 5 males and 4 females) and 18 in the elderly group (range 65 to 81 years; 9 males and 9 females). A single oral dose of zileuton 600mg was given to all volunteers on day 1 of the study and at 6-hour intervals from days 3 to 7. Analysis of variance showed slight but significant decreases in the mean apparent clearance of total and free drug in the healthy elderly population after a single zileuton dose, but no significant age-related differences after multiple 6-hourly doses. Similarly, zileuton peak and trough plasma concentrations, and values for half-life, volume of distribution and protein binding were not significantly affected by age after either a single dose or multiple administration. Moreover, gender effects on the pharmacokinetics were also absent after correction for bodyweight differences. From the results of the present study, it is concluded that there is no pharmacokinetic basis for alteration of zileuton dosage schedules in elderly patients.

Influence of age on the disposition and renal handling of enprofylline in rats

The effects of ageing on the pharmacokinetics, renal handling and protein binding of enprofylline were investigated in 6-, 13- and 18-month-old male Fischer 344 rats. Concentrations of enprofylline in plasma and urine were determined by HPLC, and pharmacokinetic parameters were estimated by model-independent methods. No significant differences in the volume of distribution, systemic clearance of enprofylline or urinary recovery of unchanged enprofylline (> 85%) were observed among any of the groups of rats. The dissociation constant and free fatty acid concentration in plasma increased with age. Age-dependent decreases in the systemic clearance for unbound drug were observed, and the volume of distribution for unbound drug tended to decrease with age. The ratio of systemic clearance for unbound drug to the glomerular filtration rate (GFR) decreased with ageing. Ageing was associated with decreases in the apparent maximum capacity of transport (Vmax)(223.33, 160.24 and 142.98 micrograms min-1 kg-1 for 6-, 13- and 18-month-old rats, respectively) and in the tubular secretory intrinsic clearance (Vmax/Km) of enprofylline (75.45, 51.03 and 44.13 mL min-1 kg-1, respectively), while a slight change in the Michaelis-Menten constant (Km) was observed. These results indicate that the mechanism responsible for age-related changes in the disposition and renal handling of enprofylline may be responsible for a decrease in the ability of the tubular anion transport system.

Age, environmental factors and drug metabolism

Both ageing and the environment have a significant impact on xenobiotic metabolism. Furthermore, there is some evidence from in vivo studies that the elderly respond to environmental changes to a lesser degree than younger individuals. This article reviews the available evidence and concentrates on possible underlying mechanisms.

Tolrestat pharmacokinetics in rat peripheral nerve

The clinical efficacy of an aldose reductase (AR) inhibitor in diabetic polyneuropathy depends on its bioavailability at the site(s) of AR in peripheral nerves. Accordingly, the link between the concentration of the AR inhibitor, tolrestat, and the extent of its inhibition of the AR-catalyzed polyol production was investigated in sciatic nerves of galactosemic rats. Tolrestat was administered by gavage (1 x 150 mg/kg, or 5, and 15 mg/kg/day for 15 days to attain steady state as estimated from the 53-h half-life of tolrestat determined in rat nerve); subsequently, at six time intervals, ranging from 4 to 59 days, rats were given access for 4 days to a 20% galactose diet, and killed. At every time point, the composite tolrestat concentration in the nerve correlated with the percentage decrease in nerve galactitol (r = 0.857, p = 0.0015). Because the latter should reflect the extent of nerve AR inhibition by tolrestat, the concentration of "free" tolrestat available at the site(s) of AR in the nerve was estimated from the tolrestat concentration/percent AR inhibition plot obtained in vitro. The estimated amount of tolrestat present at the site(s) of nerve AR represented 0.4% of the composite tolrestat concentration measured in the nerve. The results support the view that the effectiveness of an AR inhibitor in peripheral nerve depends on its pharmacokinetics in the nerve, i.e., on its uptake, nonspecific binding to cellular constituents, and elimination.

Age-related differences in the pharmacokinetics and pharmacodynamics of lansoprazole

1. The pharmacokinetics and pharmacodynamics of lansoprazole, an antisecretory and antiulcer agent, were evaluated in 12 older (> 60 years) and 12 younger (< 60 years) healthy men. 2. Doses of lansoprazole (15 or 30 mg) or placebo were each given once daily for 7 consecutive days in this randomized, double-blind, three-way crossover study. Plasma concentrations and urinary excretion of lansoprazole and its metabolites, and gastric acid secretion were monitored after dosing on days 1 and 7 of each treatment period. 3. Within each age group, lansoprazole pharmacokinetics were linear. The mean clearance and elimination half-life of lansoprazole were about 40% lower and higher, respectively, in the older subjects (CL0: 12-14 vs 20-24 1 h(-1); t1/2,z: 1.90-2.19 vs 1.26-1.44 h). 4. At each dose level, acid secretion was more inhibited in the older group. However, the AUC associated with a 50% decrease in acid secretion was similar (849 vs 892 ng ml(-1) h) for both age groups. Multiple dosing decreased the maximum possible inhibition more in the older group than in the younger group. 5. Since the decrease in acid output associated with equivalent AUCs on day 1 was similar for the two age groups, the greater difference between day 1 and day 7 secretion in the older group indicates that recovery of secretory activity may decline with increasing age.

Ketoprofen pharmacokinetics in the elderly: influence of rheumatic disease, renal function, and dose

An age-related accumulation of ketoprofen due to a reduced clearance has been reported in the elderly. Other studies have not observed these changes in the kinetics of unchanged ketoprofen, but have reported increased plasma levels and reduced urinary excretion of conjugated ketoprofen. The authors examined the effects of dose, renal function, and the presence of arthritis on the stereoselective kinetics of ketoprofen in five nonarthritic and six arthritic elderly subjects. There was a significant difference in renal function (CLCr, mL/min; arthritic, 71.8 +/- 12.3, nonarthritic, 91.4 +/- 11.1), but not in age or weight between the two groups. Subjects received 50 mg and then 150 mg enteric-coated racemic ketoprofen, and plasma and urine samples were collected for 24 hours. No significant differences in CL/F, area under the curve (AUC), half-life (t1/2), time to reach peak concentration (tmax), or maximum peak plasma concentration (Cmax) were found between groups or between doses, and values were similar to those previously reported in young adults. Urinary ketoprofen conjugate (S:R) ratio was 1.6 +/- .25 and 1.65 +/- .27 for arthritic and nonarthritic subjects. Greater amounts of conjugated ketoprofen enantiomers were present in the plasma of the arthritic compared with nonarthritic subjects. Renal clearance of ketoprofen conjugates exhibited stereoselectivity (R > S), and was decreased in the arthritic group. Significant changes in the kinetics of unchanged ketoprofen was not found to occur in elderly subjects in the presence or absence of rheumatic disease or moderate renal impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems and pitfalls of sulphonylurea therapy in older patients

The prevalence of non-insulin-dependent diabetes mellitus (type II) increases with age, so that approximately half of all known patients in English-speaking countries are over 65 years of age. There is no reason to believe that the criteria for blood glucose control should be any less stringent for elderly patients unless they have a limited life expectancy. Sulphonylurea drugs remain an effective means of achieving blood glucose control after failure of dietary therapy alone in older patients. However, changes in normal metabolism of drugs with age and the development of other pathologies in elderly patients make it important that these drugs are prescribed with care. Severe symptomatic hypoglycaemia is the most serious adverse effect of sulphonylurea drugs and this becomes progressively more likely with increasing age, depending primarily on the substantial reduction of renal function with normal aging. Other adverse effects are much less commonly of clinical importance. To minimise the risk of hypoglycaemia, it is important that patients receive closely supervised dietary management with education about their disease for at least 3 months before sulphonylurea drugs are prescribed. In elderly patients a short-acting agent with no active metabolites should be used. As patients become older, those receiving long-acting agents can be changed to short-acting agents before problems arise. If blood glucose control appears satisfactory on treatment, then symptoms of hypoglycaemia should be sought. If control is poor, then the criteria for introduction of insulin, with appropriate education, do not differ from those in younger patients.

Comparison of vancomycin pharmacokinetics in hospitalized elderly and young patients using a Bayesian forecaster

Limited data have been published that compare the pharmacokinetic parameters of vancomycin in elderly versus young patients. This study was designed to assess vancomycin pharmacokinetics in 148 elderly (> or = 60 years of age) and 140 young (18-59 years of age) hospitalized infected patients. Serum vancomycin concentrations were determined using fluorescence polarization immunoassay. Serum concentration-versus-time data were fitted to a two-compartment Bayesian forecasting program. Elderly versus young vancomycin pharmacokinetic parameters derived were as follows (patients with serum creatinine < or = 1.5 mg/dL); mean +/- standard deviation terminal disposition half-life (t1/2) of 17.8 +/- 11.8 versus 7.5 +/- 6.7 hours, respectively, P < .05; volume of distribution (Vz) of 74.2 +/- 32.3 versus 67.0 +/- 30.7 L, respectively, P = .16; and total body clearance (CL) of 0.71 +/- 0.41 versus 1.22 +/- 0.50 mL/min/kg, respectively, P < .05. Comparing subjects with normal serum creatinine values (< or = 1.5 mg/dL), the elderly required smaller daily doses as compared with the young group to maintain target peak and trough vancomycin serum concentrations (18.2 +/- 5.8 verus 25.2 +/- 7.8 mg/kg/day, P < .05). Stepwise multiple regression models for the pharmacokinetic parameters were developed to assess the predictive power of age, controlling for the effects of gender, total body weight, serum creatinine, and creatinine clearance. Age was consistently an independent and significant predictor of t1/2, Vz, and CL. These data demonstrate that elderly patients exhibit significant differences in vancomycin pharmacokinetic parameters compared with young patients and constitute a patient population in need of individualized vancomycin dosing due to substantial heterogeneity in physiologic and pharmacokinetic parameters.