Pharmacokinetic changes in the elderly. Do they contribute to drug abuse and dependence?

The factors associated with inappropriate prescription patterns of benzodiazepines and related drugs among patients with dementia

BACKGROUND

It has been emphasised that benzodiazepines and related drugs (BZDRs) should be used cautiously in people with dementia. The aim of this study was to identify factors associated with inappropriate prescription patterns of BZDRs including polypharmacy, long-term treatment and high doses among patients with dementia taking BZDRs.

METHODS

This was a retrospective chart review study of patients with dementia who were treated at the study hospital. The date that the patient was issued a catastrophic illness certificate from the National Health Insurance Administration was used as the index date. Medical records of the 2-year period after the index date were reviewed.

RESULTS

A total of 308 patients with dementia were included in this study. Among them, 151 (49.0%) received at least one prescription of BZDRs. After adjusting for covariates, psychiatric comorbidities (adjusted odds ratio (aOR) = 4.74, 95% CI = 1.75-12.81), history of past suicidal behaviour (aOR = 4.25, 95% CI = 1.40-12.88) and long-term treatment with BZDRs (aOR = 3.38, 95% CI = 1.11-10.27) were associated with polypharmacy of BZDRs. Age (aOR = 1.05, 95% CI = 1.0-1.11) and polypharmacy (aOR = 3.57, 95% CI = 1.23-10.32) were associated with long-term treatment. Living with family (aOR = 3.33, 95% CI = 1.32-9.79) and fewer psychiatric admissions to the study hospital (aOR = 0.56, 95% CI = 0.36-0.86) were associated with treatment with high doses of BZDRs.

CONCLUSIONS

Treatment with BZDRs is prevalent in patients with dementia. Inappropriate prescription patterns of BZDRs are not uncommon in these patients and may be interlinked.

Alcohol and the older adult: a comprehensive review

Alcohol consumption in the older adult is of major concern with the advent of baby boomers coming into the over 65-age bracket. Alcohol consumption has been touted as beneficial for health, and while that may be accurate for moderate consumption in younger persons, there is considerable risk associated with increased alcohol intake in older adults. This increase is partially due to age-related physiological changes, existing diagnoses, number of comorbid conditions, and increased use of prescribed and/or over-the-counter medications, coupled with other concerns. This review addresses the current research regarding ethanol consumption in older adults and all-cause mortality as well as several conditions more frequently seen in the geriatric population. These conditions include vascular diseases, hypertension, type 2 diabetes, gastrointestinal disorders, hepatic disorders, dental and oro-facial problems, bone density decline, and falls and fractures. In addition, drug interactions and recent research into select vitamin and mineral considerations with increased alcohol intake in older persons are addressed. While recommendations for alcohol intake have not been specifically established for age ranges within the 65-year-and-older bracket, and practitioners do not routinely assess alcohol intake or ethanol related adverse events in this population, common sense approaches to monitoring will become increasingly important as the generation of "boomers" who believe that alcohol intake improves health comes of age.

Causes of Rehospitalization After Renal Transplantation; Does Age of Recipient Matter?

BACKGROUND

This study assessed the causes and related factors of rehospitalization following renal transplantation among elderly compared with younger patients.

METHODS

We reviewed the charts of 567 patients rehospitalized after kidney transplantation from 2000 to 2006. According to age at the time of transplantation, hospitalizations were divided into two groups: group 1 (age >or=50 years) and group II (age 20 to 50 years). Demographics, clinical findings, causes for rehospitalization, patient outcomes (recovery, graft loss, death), intensive care unit (ICU) admission, length of hospital stay, time interval from transplantation to rehospitalization, as well as hospital costs were compared between the two groups.

RESULTS

One hundred eighty-five (32.6%) rehospitalizations were charted for group I, who showed a higher proportion of admissions due to infection (42.2% vs 29.8%, P=.004) and macrovascular disease (3.8% vs 1.0%, P=.027) compared with group II. ICU admission (8.8% vs 2.4%, P=.001), mortality (10.2% vs 3.6%, P=.008), and hospital charges (1610 +/- 933 vs 931 +/- 850 purchase power parity dollars, P=.001) were also seen more frequently in group I but displayed a lower frequency of admissions due to graft rejection (20% vs 34.3%, P=.001).

CONCLUSION

Recipient age at the time of transplantation was a main factor affecting rehospitalization among our patients.

Population pharmacokinetics and pharmacodynamics of garenoxacin in patients with community-acquired respiratory tract infections

Garenoxacin (T-3811ME, BMS-284756) is a novel, broad-spectrum des-F(6) quinolone currently under study for the treatment of community-acquired respiratory tract infections. This analysis assessed garenoxacin population pharmacokinetics and exposure-response relationships for safety (adverse effects [AE]) and antimicrobial activity (clinical cure and bacteriologic eradication of Streptococcus pneumoniae and the grouping of Haemophilus influenzae, Haemophilus parainfluenzae, and Moraxella catarrhalis). Data were obtained from three phase II clinical trials of garenoxacin administered orally as 400 mg once daily for 5 to 10 days for the treatment of community-acquired pneumonia, acute exacerbation of chronic bronchitis, and sinusitis. Samples were taken from each patient before drug administration, 2 h following administration of the first dose, and on the day 3 to 5 visit. Individual Bayesian estimates of the fu (fraction unbound), the Cmax, and the fu for the area under the concentration-time curve from 0 to 24 h (fu AUC(0-24)) were calculated as measurements of drug exposure by using an ex vivo assessment of average protein binding. Regression analysis was performed to examine the following relationships: treatment-emergent AE incidence and AUC(0-24), Cmax, or patient factors; clinical response or bacterial eradication and drug exposure (fu Cmax/MIC, fu AUC(0-24)/MIC, and other exposure covariates); or disease and patient factors. Garenoxacin pharmacokinetics were described by a one-compartment model with first-order absorption and elimination. Clearance was dependent on creatinine clearance, ideal body weight, age, obesity, and concomitant use of pseudoephedrine. The volume of distribution was dependent on weight and gender. Patients with mild or moderate renal dysfunction had, on average, approximately a 16 or 26% decrease in clearance, respectively, compared to patients of the same gender and obesity classification with normal renal function. AE occurrence was not related to garenoxacin exposure. Overall, clinical cure and bacterial eradication rates were 91 and 90%, respectively, for S. pneumoniae and 93 and 92%, respectively, for the grouping of H. influenzae, H. parainfluenzae, and M. catarrhalis. The fu AUC(0-24)/MIC ratios were high (>90% were >200), and none of the pharmacokinetic-pharmacodynamic exposure measurements indexed to the MIC or other factors were significant predictors of clinical or bacteriologic response. Garenoxacin clearance was primarily related to creatinine clearance and ideal body weight. Although garenoxacin exposure was approximately 25% higher for patients with moderate renal dysfunction, this increase does not appear to be clinically significant as exposures in this patient population were not significant predictors of AE occurrence. Garenoxacin exposures were at the upper end of the exposure-response curves for measurements of antimicrobial activity, suggesting that 400 mg of garenoxacin once daily is a safe and adequate dose for the treatment of the specified community-acquired respiratory tract infections.

Influence of age on the enantiomeric disposition of ibuprofen in healthy volunteers

AIMS

To determine the influence of age on the enantioselective disposition of ibuprofen in humans.

METHODS

Healthy young (n = 16; aged 20-36 years) and elderly (n = 16; aged 66-84 years) volunteers were given a 400-mg oral dose of racemic ibuprofen, and blood and urine samples were collected for 24 h post drug administration. Serum concentrations, total and free, and urinary excretion of both enantiomers of ibuprofen together with the urinary excretion of the stereoisomers of the two major metabolites of the drug, both free and conjugated, were determined by high-performance liquid chromatography.

RESULTS

Ageing had little effect on the distribution and metabolism of R-ibuprofen, unbound clearance of the R-enantiomer via inversion being approximately two-fold that via noninversion mechanisms in both age groups. In contrast, the free fraction of S-ibuprofen was significantly greater [33%; young 0.48 +/- 0.10%; elderly 0.64 +/- 0.20%] mean difference -0.16; 95% confidence interval (CI) -0.05, -0.27; P < 0.01; and the unbound clearance of the drug enantiomer was significantly lower (28%; young 15.9 +/- 2.2 l min-1; elderly 11.5 +/- 4.1 l min-1; mean difference 4.4; 95% CI 2.12, 6.68; P < 0.001) in the elderly. The metabolite formation clearances of S-ibuprofen via glucuronidation, and oxidation at the 2- and 3- positions of the isobutyl side chain decreased by 24, 28 and 30%, respectively, in the elderly compared with the young, the differences between the two age groups being significant in each case (P < 0.05).

CONCLUSIONS

Following administration of racemic ibuprofen age-associated stereoselective alterations in drug disposition have been observed, with the elderly having increased free concentrations and lower unbound clearance of the S-enantiomer in comparison with the young. In contrast, the handling of the R-enantiomer is essentially unaltered with age. The results of this study indicate that the elderly have an increased exposure to the active ibuprofen enantiomer and thus some caution may be required when using this drug in this age group.

Is there a rationale for prescription of benzodiazepines in the elderly? Review of the literature

Benzodiazepines (BZDs) constitute the most widely used symptomatic treatment of insomnia and anxiety. Many of these drugs are associated with adverse effects, such as daytime sedation and dependence with continued use. There is a concern about the rationale for and extent of benzodiazepine (BZD) use in the elderly. The sedation due to BZD use is a main risk factor for falls and other accidents. Impaired cognitive function with continuous use appears to be a major side effect. There is a general awareness that BZD use is inappropriate in many patients, and therefore discontinuation should be recommended whenever possible. Moreover, long-term use of these drugs should be actively discouraged. Although no unanimous recommendations concerning the optimal duration of the withdrawal process exist, BZDs may easily be withdrawn during a short period in most patients who are habituated to a low dose, if an initial phase with dose reduction and psychological support are provided. Alternative approaches involve sleep hygiene guidelines, behavioural treatment and psychotherapy tailored to the needs of the individual patient.

Clinically Important Drug Interactions with Intravenous Anaesthetics in Older Patients

There is a continuously growing population of older surgical patients who require an increasing number of anaesthetics and sedation. Pharmacokinetic and pharmacodynamic changes associated with increasing age are often not appreciated enough. Dose requirements for midazolam, a benzodiazepine commonly used for outpatient procedures, have been demonstrated in prospective studies to decrease with increasing age. On the other hand, rigorous prospective studies investigating the effect of age on the induction doses of other intravenous anaesthetics, such as thiopental sodium or propofol, are missing. In addition, many of those patients take multiple drugs for medical problems often not related to the procedure. Drug interactions with anaesthetics are likely to occur, but are not well documented. In this review we have summarised the documented and clinically relevant drug interactions with anaesthetics in the elderly population. We have identified a significant lack of scientific and outcome data and the need for more studies and education.

Personality traits and socio-epidemiological status of hospitalised elderly benzodiazepine users

OBJECTIVE

to define personality traits and socio-epidemiological status of hospitalised elderly chronic benzodiazepine (BZD) users.

METHODS

this case controlled study assessed psychological characteristics (using the Millon Clinical Multiaxial Inventory-MCMI-I) and socio-epidemiological status (sex, age, education, marital status and housing) in 40 hospitalised geriatric patients taking BZDs for at least 3 months and 40 non-users, excluding dementia.

RESULTS

comparisons between groups: Compulsive personality pattern was more pronounced in the control group (p = 0.008). Severe personality pathology: a predisposition to borderline disorder was stronger among the BZD-users (p = 0.001). Clinical syndromes: anxiety, dysthymic disorder (p < 0.001) and tendency to alcohol dependence (p = 0.020) prevailed in the BZD-users. No severe syndromes were found. Widowed persons were more prevalent between the BZD-users (p = 0.03). All significant differences resulted from disparities between females. Predictors of BZD-use and clustering of traits: Dysthymic disorder was predictive of BZD-use (odds ratio (OR) 6.3 [95% confidence intervals (CI) 2.2-18.2]). It was strongly correlated with anxiety (r(s) = 0.93) and somatoform disorder (r(s) = 0.71). Dysthymic disorder and alcohol dependence predicted BZD-use in women (OR 15.3 [CI: 2.4-95.7] and OR 9.1 [CI: 1.2-64.9], respectively). There were no specific predictors in men.

CONCLUSIONS

chronic elderly BZD-users are typically widowed females with dysthymic disorder, anxiety, predisposition to alcohol dependence and borderline disorder. Before prescribing BZDs, it is important to recognize the nature of the elderly population at risk for BZD-use and to consider a broader-ranging therapeutic management of the predisposing personality traits.

Smoking in patients receiving psychotropic medications: a pharmacokinetic perspective

Many psychiatric patients smoke, and are believed to be heavier smokers than those without psychiatric disorders. Cigarette smoking is one of the environmental factors that contributes to interindividual variations in response to an administered drug. Polycyclic aromatic hydrocarbons (PAHs) present in cigarette smoke induce hepatic aryl hydrocarbon hydroxylases, thereby increasing metabolic clearance of drugs that are substrates for these enzymes. PAHs have been shown to induce 3 hepatic cytochrome P450 (CYP) isozymes, primarily CYP1A1, 1A2 and 2E1. Drug therapy can also be affected pharmacodynamically by nicotine. The most common effect of smoking on drug disposition in humans is an increase in biotransformation rate, consistent with induction of drug-metabolising enzymes. Induction of hepatic enzymes has been shown to increase the metabolism and to decrease the plasma concentrations of imipramine, clomipramine, fluvoxamine and trazodone. The effect of smoking on the plasma concentrations of amitriptyline and nortriptyline is variable. Amfebutamone (bupropion) does not appear to be affected by cigarette smoking. Smoking is associated with increased clearance of tiotixene, fluphenazine, haloperidol and olanzapine. Plasma concentrations of chlorpromazine and clozapine are reduced by cigarette smoking. Clinically, reduced drowsiness in smokers receiving chlorpromazine, and benzodiazepines, compared with nonsmokers has been reported. Increased clearance of the benzodiazepines alprazolam, lorazepam, oxazepam, diazepam and demethyl-diazepam is found in cigarette smokers, whereas chlordiazepoxide does not appear to be affected by smoking. Carbamazepine appears to be minimally affected by cigarette smoke, perhaps because hepatic enzymes are already stimulated by its own autoinductive properties. Cigarette smoking can affect the pharmacokinetic and pharmacodynamic properties of many psychotropic drugs. Clinicians should consider smoking as an important factor in the disposition of these drugs.

Analysis of the CYP2D6 gene polymorphism and enzyme activity in African-Americans in southern California

Despite its importance in drug metabolism and disease susceptibility, CYP2D6 activity and genetic polymorphism have rarely been investigated in African-American populations. In order to bridge this gap, we examined the genotype and phenotype of the enzyme in 154 African-American (AA) and 143 Caucasian (C) normal volunteers. AAs are significantly more likely to possess *17 and *5, but less likely to have *4. Overall, the two groups were similar in their CYP2D6 activity as measured with dextromethorphan as the probe (metabolic ratio 2.21 +/- 0.78 for AAs; 2.11 +/- 0.86 for Cs; t = 1.02, NS). Two of four AAs and six of seven Cs were classified as poor metabolizers and have two nonfunctioning alleles. CYP2D6 activity is determined by *17, *4, *5 and age in AAs (r2 = 0.33, f = 18.8, P < 0.001) and by *4 and *XN in Cs (r2 = 0.14, f = 10.8, P < 0.001). These results support previous findings demonstrating the importance of *17 in determining CYP2D6 activity in AAs.

Pharmacokinetic and pharmacodynamic changes in the elderly. Clinical implications

Age-related changes in pharmacokinetics principally affect drug absorption, distribution, metabolism and elimination. Changes in pharmacodynamics are primarily seen in the cardiovascular and neuroendocrine system. Age-dependent changes in the kinetics and dynamics of drugs acting on the cardiovascular system and central nervous system are common, and this review, while by no means exhaustive of the effects of drugs on all organ systems, is reflective of the principles and gives examples of the effects of age on these 2 major systems. While pharmacokinetic changes in the elderly are usually well characterised, pharmacodynamic changes are understood only in the most preliminary way. There has been relatively little research in this area of geriatric clinical pharmacology, and pharmacodynamic changes are still an area of investigation.

Pharmacokinetics and the pharmacodynamic action of midazolam in young and elderly patients undergoing tooth extraction

OBJECTIVE

To determine whether age-dependent pharmacokinetic and pharmacodynamic alterations account for a more pronounced response to benzodiazepines among elderly patients.

METHODS

Twelve young patients and 10 elderly patients received an intravenous dose of 0.05 or 0.03 mg/kg midazolan, respectively, before third molar extraction. Postoperative pain was treated with 30 mg dihydrocodeine. Serum concentrations of midazolam and sedative effects were monitored with visual analog scales and choice reaction time measurements for 6 hours. Test values above baseline were integrated, and pharmacokinetic-pharmacodynamic analysis was performed. Heart rate, blood pressure, arterial oxygen saturation, and amnesia also were assessed.

RESULTS

There were no significant age-dependent differences in disposition of midazolam between young and elderly patients (apparent volume of distribution, 1.3 +/- 0.2 versus 1.1 +/- 0.4 L/kg; halflife, 3.3 +/- 1.5 hours versus 3.7 +/- 2.2 hours; total body clearance, 451 +/- 186 ml/min versus 343 +/- 137 ml/min). However, higher values of area under the effect curve (AUEC) and AUEC divided by area under the serum concentration-time curve (AUC) (sensitivity index) were observed among the elderly as follows: AUEC for reaction time (AUECRT) (573 versus 261; p = 0.042), AUEC for visual analog scale (AUECVAS) (37.7 versus 14.4; p = 0.011), AUECRT/AUC (6.3 versus 1.8; p = 0.007), and AUECVAS/AUC (0.40 versus 0.11; p = 0.009) compared with the young group. Likewise, mean concentration at half-maximal effect for sedation was lower (p = 0.025) among older patients (20.5 +/- 2.2 ng/ml) than among younger (29.7 +/- 6.6 ng/ml) patients. Amnesia was observed among 86% of patients and oxygen saturation was always 95% or more of basal value. There were no age-related differences in concentration of dihydrocodeine and its active metabolite dihydromorphine, but dihydromorphone levels were much lower in there intermediate metabolizers (455 to 879 fmol/l) and especially in five poor metabolizers (65 to 498 fmol/L) than among extensive metabolizer of cytochrome p450 2D6 (1604 to 6490 fmol/L).

CONCLUSION

Elderly patients are more sensitive to the sedative action of midazolam than young patients, and the sensitivity is caused by age-dependent pharmacodynamic alterations. The age-adjusted doses used are both effective (for sedative amnesia) and safe (in terms of arterial oxygen saturation, heart rate, and blood pressure.