Age, environmental factors and drug metabolism

Efficacy and Safety of Megestrol in the Hospitalized Older Person

Objectives To evaluate the efficacy and safety of megestrol for off-label use in older patients with weight loss. Design Retrospective, nonblinded cohort study. Setting Upstate University Hospital is a 420-bed facility and academic medical center with a level 1 trauma center. Upstate Community Hospital is a 314-bed acute care/hospital/ambulatory care center and long-term care hospital that also provides teaching services. Participants Patients 65 years of age and older without malignancy or acquired immunodeficiency syndrome who were initiated and continued megestrol therapy at the Upstate University hospitals for at least two weeks were included. Of the 1,290 patients initially screened, 16 patients on megestrol were evaluated. An age- and gender-matched control group of 16 patients was utilized for comparison of changes in weight and other variables. Interventions Patients in the megestrol group have received daily doses of megestrol between 160 mg to 800 mg for an average duration of 19 days. Patients in the control group had no history or current use of megestrol utilization. Main Outcome Measurements The primary outcome was an increase in weight. Secondary outcome measures included albumin and thromboembolic events. Changes in weight and albumin were also compared with the control group. Results At a mean duration of 19 days, there was no significant difference in weight gain (0.95 kg, OR = 1.33 [95% CI -1.615-3.527]). Albumin decreased by (0.4 g/dL OR = 0.916 [95% CI 0.12-0.78]) and none of the patients developed a thromboembolic event. Conclusion In older hospitalized patients, megestrol did not increase weight, and did not improve albumin. No thromboembolic events were observed, but this may be because of a limited duration of observation of therapy and the routine use of anticoagulation prophylaxis in the inpatient setting.

Role of Pharmacogenetics in Adverse Drug Reactions: An Update towards Personalized Medicine

Adverse drug reactions (ADRs) are an important and frequent cause of morbidity and mortality. ADR can be related to a variety of drugs, including anticonvulsants, anaesthetics, antibiotics, antiretroviral, anticancer, and antiarrhythmics, and can involve every organ or apparatus. The causes of ADRs are still poorly understood due to their clinical heterogeneity and complexity. In this scenario, genetic predisposition toward ADRs is an emerging issue, not only in anticancer chemotherapy, but also in many other fields of medicine, including hemolytic anemia due to glucose-6-phosphate dehydrogenase (G6PD) deficiency, aplastic anemia, porphyria, malignant hyperthermia, epidermal tissue necrosis (Lyell's Syndrome and Stevens-Johnson Syndrome), epilepsy, thyroid diseases, diabetes, Long QT and Brugada Syndromes. The role of genetic mutations in the ADRs pathogenesis has been shown either for dose-dependent or for dose-independent reactions. In this review, we present an update of the genetic background of ADRs, with phenotypic manifestations involving blood, muscles, heart, thyroid, liver, and skin disorders. This review aims to illustrate the growing usefulness of genetics both to prevent ADRs and to optimize the safe therapeutic use of many common drugs. In this prospective, ADRs could become an untoward "stress test," leading to new diagnosis of genetic-determined diseases. Thus, the wider use of pharmacogenetic testing in the work-up of ADRs will lead to new clinical diagnosis of previously unsuspected diseases and to improved safety and efficacy of therapies. Improving the genotype-phenotype correlation through new lab techniques and implementation of artificial intelligence in the future may lead to personalized medicine, able to predict ADR and consequently to choose the appropriate compound and dosage for each patient.

Functional phenotyping of the CYP2D6 probe drug codeine in the horse

BACKGROUND

In humans, the drug metabolizing enzyme CYP2D6 is highly polymorphic resulting in substantial differences in the metabolism of drugs including anti-arrhythmics, neuroleptics, and opioids. The objective of this study was to phenotype a population of 100 horses from five different breeds and assess differences in the metabolic activity of the equine CYP2D6 homolog using codeine as a probe drug. Administration of a probe drug is a common method used for patient phenotyping in human medicine, whereby the ratio of parent drug to metabolite (metabolic ratio, MR) can be used to compare relative enzyme function between individuals. A single oral dose of codeine (0.6 mg/kg) was administered and plasma concentrations of codeine and its metabolites were determined using liquid chromatography mass spectrometry. The MR of codeine O-demethylation [(codeine)/(morphine + morphine-3-glucuronide + morphine-6-glucuronide)] was determined using the area under the plasma concentration-time curve extrapolated from time zero to infinity (AUC0-∞) for each analyte and used to group horses into predicted phenotypes (high-, moderate-, and low-MR).

RESULTS

The MR of codeine O-demethylation ranged from 0.002 to 0.147 (median 0.018) among all horses. No significant difference in MR was observed between breeds, age, or sex. Of the 100 horses, 11 were classified as high-MR, 72 moderate-MR, and 17 low-MR. Codeine AUC0-∞ and O-demethylation MR were significantly different (p < 0.05) between all three groups. The mean ± SD MR was 0.089 ± 0.027, 0.022 ± 0.011, and 0.0095 ± 0.001 for high-, moderate-, and low-MR groups, respectively. The AUC for the morphine metabolites morphine-3-glucuronide and morphine-6-glucuronide were significantly different between high-and low-MR groups (p < 0.004 and p < 0.006).

CONCLUSIONS

The MR calculated from plasma following codeine administration allowed for classification of horses into metabolic phenotypes within a large population. The range of codeine metabolism observed among horses suggests the presence of genetic polymorphisms in CYP2D82 of which codeine is a known substrate. Additional studies including CYP2D82 genotyping of high- and low-MR individuals are necessary to determine the presence of CYP2D polymorphisms and their functional implications with respect to the metabolism of therapeutics.

Hepatic Transcript Levels for Genes Coding for Enzymes Associated with Xenobiotic Metabolism are Altered with Age

Metabolism studies are crucial for data interpretation from rodent toxicity and carcinogenicity studies. Metabolism studies are usually conducted in 6 to 8 week old rodents. Long-term studies often continue beyond 100 weeks of age. The potential for age-related changes in transcript levels of genes encoding for enzymes associated with metabolism was evaluated in the liver of male F344/N rats at 32, 58, and 84 weeks of age. Differential expression was found between the young and old rats for genes whose products are involved in both phase I and phase II metabolic pathways. Thirteen cytochrome P450 genes from CYP families 1–3 showed alterations in expression in the older rats. A marked age-related decrease in expression was found for 4 members of the Cyp3a family that are critical for drug metabolism in the rat. Immunohistochemical results confirmed a significant decrease in Cyp3a2 and Cyp2c11 protein levels with age. This indicates that the metabolic capacity of male rats changes throughout a long-term study. Conducting multiple hepatic microarray analyses during the conduct of a long-term study can provide a global view of potential metabolic changes that might occur. Alterations that are considered crucial to the interpretation of long-term study results could then be confirmed by subsequent metabolic studies.

The pattern and risk factors associated with adverse drug reactions induced by Reteplase in patients with acute ST-elevation myocardial infarction: The first report from Iranian population

Objective:

Acute myocardial infarction (AMI) is one of the main leading causes of mortality and morbidity. Reteplase is a fibrin-specific thrombolytic which is used in the treatment of AMI. There is a limited number of studies reporting the postmarketing adverse drug reactions (ADRs) induced by reteplase. This study was aimed to examine the reteplase pattern of ADR and its associated risk factors in patients with acute ST-elevation myocardial infarction.

Methods:

A cross-sectional, prospective study in an 8-month period was done at the University affiliated referral cardiovascular center. The Naranjo probability scale and World Health Organization criteria for severity of ADRs were used for assessing the ADRs. The linear regression and logistic regression tests were used to evaluate the correlation between ADRs and risk factors.

Findings:

The all 20 patients who received reteplase during the study period were entered. The majority of patients (n = 17) experienced at least one ADR. The results showed that the incidence of ADRs was mainly associated with gender and age, and the number of ADRs was associated with the history of diabetes and taking anti-diabetic agents. The gender was the main predictor in the occurrence of ADRs (odds ratio: 32, 95% confidence interval: 1.38–737.45; P = 0.030).

Conclusion:

The results showed that gender, age, diabetes mellitus, and using of anti-diabetes medications are the risk factors associated with the incidence of ADRs by reteplase.

Adverse drug reactions in older people: detection and prevention

Adverse drug reactions (ADRs) in older adults are an important healthcare problem since they are frequently a cause of hospitalization, occur commonly during admission, and are an important cause of morbidity and mortality. Older adults are particularly susceptible to ADRs because they are usually on multiple drug regimens and because age is associated with changes in pharmacokinetics and pharmacodynamics. The presentation of an ADR in older adults is often atypical, which further complicates its recognition. One potential strategy for improving recognition of ADRs is to identify those patients who are at risk of an ADR. The recently developed GerontoNet ADR Risk Score is a practical tool for identification of older patients who are at increased risk for an ADR and who may represent a target for interventions aimed at reducing ADRs. Provision of adequate education in the domain of clinical geriatric pharmacology can improve recognition of ADRs. Besides formal surveillance systems, built-in computer programs with electronic prescribing databases and clinical pharmacist involvement in patient care within multidisciplinary geriatric teams might help to minimize the occurrence of ADRs. In addition, a number of actions can be taken in hospitals to stimulate appropriate prescribing and to assure adequate communication between primary and hospital care. In older adults with complex medical problems and needs, a global evaluation obtained through a comprehensive geriatric assessment may be helpful in simplifying drug prescription and prioritizing pharmacological and healthcare needs, resulting in an improvement in quality of prescribing.

Elderly and drugs: risks and necessity of rational use

In recent decades, the world has undergone a demographic transformation with a rapid growth of the elderly population, resulting in an increased demand for funds to maintain their health and drug consumption. Pharmacokinetic and pharmacodynamic changes occurring in the elderly can interfere directly in the adverse effects of drugs and increase the risk of intoxication. In addition, there are external factors interfering with the pharmacotherapy of the elderly, such as inappropriate use and the lack of access to information. Many therapeutic classes of drugs should be used with caution or avoided in the elderly population, such as anti-inflammatory and some anti-hypertensive drugs, diuretics and digitalis. If not managed carefully, these medicines can affect the safety and quality of life in the elderly. Thus, the aim of this review was to identify drugs that should be used with caution in elderly patients in order to avoid intoxication and/or adverse drug events.

Chronic obstructive pulmonary disease in the elderly: an update on pharmacological management

The prevalence of chronic obstructive pulmonary disease (COPD) continues to rise in association with an aging Western society. While barriers to receiving optimal healthcare exist for aging patients, pharmacotherapy of COPD in the elderly is important because the treatment benefits in this group are comparable to those seen in the younger COPD population. The frequent presence of co-morbidities and reduced clearance capacity make selection of pharmacotherapy in elderly patients with stable COPD challenging. The adverse effects of standard therapy for COPD may also be more pronounced in elderly patients. A careful risk-versus-benefit assessment should always be carried out when prescribing long-term inhaled bronchodilator and corticosteroid therapy to an elderly COPD patient, and when prescribing beta(2)-adrenoceptor agonists and methylxanthines, in particular, to those with cardiovascular co-morbidities. The present review focuses on the special considerations regarding initiation and maintenance of pharmacotherapy in elderly patients with stable COPD.

Assessment of tolerability in elderly patients: Changing to lamotrigine therapy

BACKGROUND

Of all age groups, adults older than 75 years have the highest risk of seizures, especially partial seizures. In the past, physicians commonly used phenytoin, carbamazepine, and valproic acid as antiepileptic drugs (AEDs) in the elderly. However, these AEDs have potential adverse effects and drug interactions that may make them less desirable than newer AEDs for this age group.

OBJECTIVES

The primary objective of this study was to assess the effects of changing the AED regimen to lamotrigine (LTG) in elderly patients (aged >or=60 years) who were initially unsatisfied with their drug regimen because of adverse effects or continuing seizures. These patients comprised a subgroup from a multicenter, open-label trial of partial-seizure patients who switched to LTG. Other objectives included assessing the change in quality of life in patients taking LTG as adjunctive therapy and as monotherapy, and evaluating the efficacy of LTG for seizures when used as adjunctive treatment and as monotherapy.

METHODS

The study involved 2 phases: LTG was first added to the regimen, and then patients could change to LTG monotherapy. Tolerability, the primary end point, was assessed using the Liverpool Adverse Experience Profile (AEP). Secondary end points included quality of life, as measured with the Quality of Life in Epilepsy-31 inventory, investigator global assessment, patient's self-rated satisfaction with treatment, and Profile of Mood States. The proportion of patients who completed each phase with at least a 50% reduction in seizures from baseline and the proportion of patients remaining seizure free throughout each phase were also determined.

RESULTS

Sixty-two patients aged >or=60 years (mean [SD]age, 71.3 [7.6] years; 31 men, 31 women) were enrolled. After adding LTG, older patients reported fewer adverse effects, improved mood, better quality of life, and fewer seizures. Changing to LTG as monotherapy produced further improvement in all measurements. For the primary end point, mean improvement in AEP scores from baseline was 2.3 at the end of the adjunctive therapy phase (P = 0.027) and 5.7 by the end of the monotherapy phase (P < 0.005). In addition, there was a mean improvement of 2.0 in the AEP score from the adjunctive therapy to the monotherapy phase.

CONCLUSIONS

For older patients with seizures who were unhappy with their AED regimen because of adverse effects, continuing seizures, or both, adding LTG to the drug regimen was associated with improved tolerability and effectiveness, and switching to LTG monotherapy was associated with further improvement.

Outcomes in Elderly Patients With Newly Diagnosed and Treated Epilepsy

Epilepsy develops most commonly in the elderly. Seizures can severely affect a senior citizen's quality of life, and despite a growing elderly population with epilepsy, there is a paucity of good clinical data in this age group. To address some of the issues encountered by elderly patients with epilepsy, prospective information from elderly patients attending the Epilepsy Unit at the Western Infirmary in Glasgow, Scotland, was analyzed. Ninety patients, aged 65-93 years, were diagnosed with epilepsy and started on antiepileptic drug (AED) treatment. Neuroimaging was performed in 84 patients (93%), with 69 evaluated via computerized tomography and 15 via magnetic resonance imaging; abnormalities were found in 45 patients (54%). Sixty-eight patients underwent interictal electroencephalography, which revealed epileptiform discharges in 18 patients (26%). Fifty-eight of 90 patients (64%) became seizure free for at least 12 months on modest doses of the first prescribed AED. Seizures remained uncontrolled in 21 patients (23%), and the first AED was withdrawn in 11 patients (12%) because of adverse events. Following pharmacological manipulation, a total of 76 patients (84%) achieved seizure freedom. Patients starting treatment > or =2 years after their first seizure were less likely to achieve seizure control than patients who initiated treatment earlier. Newly diagnosed elderly patients were more likely to remain seizure free on AED treatment than newly diagnosed younger populations (p < 0.001). The majority of patients evaluated had partial-onset seizures, and underlying cerebral atrophy and infarcts were common. Treating an older person with initial AED therapy can be complicated; taking adequate time and communicating clearly are paramount. Although most of the patients evaluated had a positive outcome, all AEDs have some disadvantages in this population. Choice of drug may depend on comorbidity and comedication, among other factors. Initial dosing should be low with a slow titration schedule. A holistic approach to care helps optimize the outcome for elderly people with epilepsy.

Population pharmacokinetic modelling of carbamazepine in epileptic elderly patients: implications for dosage

BACKGROUND

Proper use of antiepileptic drugs in the elderly involves knowledge of their pharmacokinetics to ensure a patient-specific balance between efficacy and toxicity. However, populations of epileptic patients on chronic carbamazepine (CBZ) therapy which have been studied have included data of relatively few elderly patients.

AIMS

The aim of the present study was to evaluate the population pharmacokinetics of CBZ in elderly patients on chronic monotherapy.

METHODS

We have used the non-parametric expectation maximization (NPEM) program in the USC*PACK collection of PC programs to estimate individual and population post-induction pharmacokinetics of CBZ in epileptic elderly patients who received chronic CBZ monotherapy. Age-related changes of CBZ population pharmacokinetics were evaluated from routine therapeutic drug monitoring (TDM) data of 37 elderly and 35 younger patients with epilepsy. As a 'historical control' we used previously published population modelling results from 99 young epileptic patients on chronic CBZ monotherapy. In that control group, TDM was performed in the same pharmacokinetic (PK) laboratory, using the same sampling strategy as in the present study, and the same PK population modelling software was used for data analysis.

RESULTS AND CONCLUSIONS

A poor correlation was found between daily CBZ dose and serum concentrations in the elderly patients (r=0.2, P=0.25). Probably statistically significant difference in the median values of the CBZ metabolic rate constant (P<0.001) between elderly and relatively young epileptic patients was found. Our results showed that age-related influences in CBZ pharmacokinetics in elderly patients should be considered in the optimal planning of CBZ dosage regimens. Most elderly patients with epilepsy will usually need CBZ dosages lower than those based on the median population PK parameter values obtained from younger patients. The present population model is also uniquely well suited for the new 'multiple model' design of dosage regimens to hit target therapeutic goals with maximum precision.

Drug metabolism and ageing

Important changes in drug metabolism occur with ageing. Age-associated reductions in function of some but not all cytochrome P450 enzymes (CYPs) have been described. Induction and inhibition of CYPs needs to be revisited in light of recent advances. The function and pharmacology of transporters have not yet been examined for an age-related effect. Finally, the concept of frailty is being underpinned by studies documenting a decline in drug metabolism and changes in disposition in frail older people compared with either healthy elderly or the young.

Adverse drug reactions in elderly patients

Many studies from around the world show a correlation between increasing age and adverse drug reaction (ADR) rate, at least for some medical conditions. More than 80% of ADRs causing admission or occurring in hospital are type A (dose-related) in nature, and thus predictable from the known pharmacology of the drug and therefore potentially avoidable. Frail elderly patients appear to be particularly at risk of ADRs and this group is also likely to be receiving several medicines. The toxicity of some drug combinations may sometimes be synergistic and be greater than the sum of the risks of toxicity of either agent used alone. In order to recognize and to prevent ADRs (including drug interactions), good communication is crucial, and prescribers should develop an effective therapeutic partnership with the patient and with fellow health professionals. Undergraduate and postgraduate education in evidence-based therapeutics is also vitally important. The use of computer-based decision support systems (CDSS) and electronic prescribing should be encouraged, and when problems do occur, health professionals need to be aware of their professional responsibility to report suspected adverse drug events (ADEs) and ADRs. "Rational" or "obligatory" polypharmacy is becoming a legitimate practice as increasing numbers of individuals live longer and the range of available therapeutic options for many medical conditions increases. The clear risk of ADRs in this situation should be considered in the context that dose-related failure of existing therapy to manage the condition adequately may be one of the most important reasons for admission of the elderly to hospital. Thus, age itself should not be used as a reason for withholding adequate doses of effective therapies.

Effects of Malnutrition on Cytochrome P450 1A2 Activity in Elderly Patients

Little is known of the influence of nutritional status on cytochrome P450 (CYP) 1A2 activity in elderly patients. Thirty elderly institutionalised patients with malnutrition (group A, aged 88 +/- 5 years) and 24 without (group B, aged 81 +/- 9 years) were included. Malnutrition was defined as weight loss of >10% over the previous 6 months and/or a body mass index (BMI) <21 kg/m2 and albuminaemia < or = 32 g/L. CYP1A2 activity was evaluated by the plasma paraxanthine/caffeine (PAX/CAF) metabolic ratio. The plasma PAX/CAF metabolic ratio was similar in both groups regardless of nutritional status (0.34 +/- 0.13 [A] versus 0.30 +/- 0.11 [B]; p = 0.11). The CYP1A2 metabolic ratio was not correlated to either BMI, serum albumin or renal clearance. CYPI A2 activity, as measured by the plasma PAX/CAF ratio, was not influenced by nutritional status in elderly patients.

Intraocular pressure in genetically distinct mice: an update and strain survey

BACKGROUND

Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. The purpose of this study was to determine the IOPs of genetically distinct mouse strains, assess the effects of factors such as age, sex and time of day on IOP in specific strain backgrounds, and to assess the effects of specific candidate gene mutations on IOP.

RESULTS

Based on over 30 studied mouse strains, average IOP ranges from approximately 10 to 20 mmHg. Gender does not typically affect IOP and aging results in an IOP decrease in some strains. Most tested strains exhibit a diurnal rhythm with IOP being the highest during the dark period of the day. Homozygosity for a null allele of the carbonic anhydrase II gene (Car2n) does not alter IOP while homozygosity for a mutation in the leptin receptor gene (Leprdb) that causes obesity and diabetes results in increased IOP. Albino C57BL/6J mice homozygous for a tyrosinase mutation (Tyrc-2J) have higher IOPs than their pigmented counterparts.

CONCLUSIONS

Genetically distinct mouse strains housed in the same environment have a broad range of IOPs. These IOP differences are likely due to interstrain genetic differences that create a powerful resource for studying the regulation of IOP. Age, time of day, obesity and diabetes have effects on mouse IOP similar to those in humans and other species. Mutations in two of the assessed candidate genes (Lepr and Tyr) result in increased IOP. These studies demonstrate that mice are a practical and powerful experimental system to study the genetics of IOP regulation and disease processes that raise IOP to harmful levels.

Clinical pharmacokinetics of goserelin

Goserelin is a synthetic decapeptide analogue of luteinising hormone-releasing hormone (LHRH). For experimental purposes it has been administered subcutaneously as an aqueous solution, but for therapeutic use it is formulated as subcutaneous depots releasing goserelin over periods of 1 (3.6 mg) or 3 (10.8 mg) months. Pharmacokinetic data have been generated using a specific radioimmunoassay. When administered as a solution, goserelin is rapidly absorbed and eliminated from serum with a mean elimination half-life (t1/2beta) of 4.2 hours in males and 2.3 hours in females. The shapes of the observed serum goserelin profiles following administration of the depots are primarily determined by the rate of goserelin release from the biodegradable lactide-glycolide copolymer matrix over periods of 1 or 3 months. There is no clinically relevant accumulation of goserelin during multiple administration of these depots. Goserelin is extensively metabolised prior to excretion. Its pharmacokinetics are unaffected by hepatic impairment, but the mean t1/2beta increases to 12.1 hours in patients with severe renal impairment. This suggests that the total renal clearance (renal metabolism and unchanged drug) is decreased in patients with renal dysfunction. It is unnecessary to adjust the dose or administration interval when the depot formulations are administered to elderly patients or to those with impaired renal or hepatic function. Administration of a goserelin 3.6 mg or 10.8 mg depot results in an initial increase of luteinising hormone (LH) levels and in increases of serum testosterone or oestradiol levels in males and females, respectively. This is followed by a decrease in serum LH levels and suppression of testosterone or oestradiol to within the castrate or menopausal range, respectively. Subsequently, throughout treatment with goserelin depots, serum testosterone or oestradiol levels remain suppressed. Clinical outcomes following treatment of patients with prostate cancer, breast cancer and benign gynaecological conditions with goserelin are described briefly.

Epilepsy in elderly people

The prevalence and incidence of epilepsy are highest in later life with around 25% of new cases occurring in elderly people, many of whom will have concomitant neurodegenerative, cerebrovascular, or neoplastic disease. Difficulties accepting the diagnosis are frequently compounded by its unpredictable nature. Those affected commonly lose confidence and independence. Seizures in older people can result in physical injury, adding to low morale. Complete control is achievable in around 70% of patients with antiepileptic drug treatment. Optimum management requires rapid investigation, accurate diagnosis, effective treatment, sympathetic education, and assured support. The emergence of seizure disorders in old age places an increasing burden on health-care facilities and costs. A coordinated programme among health-care workers is advised to maintain the independence and improve the quality of life of this vulnerable patient population.

Multicentre, double-blind, randomised comparison between lamotrigine and carbamazepine in elderly patients with newly diagnosed epilepsy. The UK Lamotrigine Elderly Study Group

In a multicentre, double-blind trial 150 elderly patients (mean age 77 years) with newly diagnosed epilepsy were randomised in a 2:1 ratio to treatment with lamotrigine (LTG) or carbamazepine (CBZ). Following a short titration period, the dosage was individualised for each patient while maintaining the blind over the next 24 weeks. The main difference between the groups was the rate of drop-out due to adverse events (LTG 18% versus CBZ 42%). This was in part a consequence of the lower rash rate with LTG (LTG 3%, CBZ 19%; 95% CI 7-25%). LTG-treated patients also complained less frequently of somnolence (LTG 12%, CBZ 29%; 95% CI 4-30%). Although there was no difference between the drugs in time to first seizure, a greater percentage of LTG-treated patients remained seizure-free during the last 16 weeks of treatment (LTG 39%, CBZ 21%; P = 0.027). Overall, more patients continued on treatment with LTG than CBZ (LTG 71%, CBZ 42%; P < 0.001) for the duration of the study. The hazard ratio for withdrawal was 2.4 (95% CI 1.4-4.0) indicating that a patient treated with CBZ was more than twice as likely to come off medication than one taking LTG. In conclusion, LTG can be regarded as an acceptable choice as initial treatment for elderly patients with newly diagnosed epilepsy.

Age-dependent changes in rat liver microsomal membrane structure and functions under benzene treatment

The influence of benzene on 3 and 24 months old rat liver microsomes was studied. Some structural and functional changes occur under benzene treatment in the cytochrome P-450 system which are more pronounced in 3 months old rat microsomes than in the 24 months ones. Glucose-6-phosphatase and glucose dehydrogenase activities indicate that 3 months old rat microsomal vesicles are more stable against benzene injury than those, of 24 months old ones. In vitro benzene hydroxylation activation by NADPH addition decreased disruptive xenobiotic's effect on 3 but not on 24 months old rat liver microsomal vesicles. This fact suggests that the rate of benzene hydroxylation is important for its membrane damaging action effect. Thus, age-related differences in xenobiotic action on liver microsomes could be related to the decrease of benzene metabolism rate with senescence.

Cognitive effects of anticonvulsant monotherapy in elderly patients: a placebo-controlled study

Old age is recognized to be the commonest time in life to develop epilepsy. There is a perception that older patients are more sensitive to the deleterious cognitive effects of antiepileptic drugs (AEDs). Elderly patients (median age 70 years, range 60-88 years) taking anticonvulsant monotherapy (10 carbamazepine [CBZ], 8 sodium valproate [VPA], 5 phenytoin [PHT]) took an extra dose of their usual medication (200mg CBZ, 500mg VPA, 100mg PHT) and matched placebo each for a month in random order. The concentrations of AEDs were higher after 7 and 28 days of active treatment compared with placebo (7 days: CBZ 9.5 vs. 7.8 mg L(-1), p < 0.05; VPA 97 vs. 64 mg L(-1), p < 0.05; PHT 13 vs. 11 mg L(-1), p < 0.05; 28 days: CBZ 9.4 vs. 7.7 mg L(-1); p < 0.01, VPA 85 vs. 60 mg L(-1), p < 0.05; PHT 16 vs. 13 mg L(-1), p < 0.05). Despite these increases in concentration, there were no significant changes in attention, reaction time, finger tapping, memory, side-effect scale or sedation scoring during the active phases compared with placebo phases for the three drugs analysed together and separately. Elderly patients taking standard AEDs as monotherapy did not develop cognitive impairment when the dose was modestly increased within the target range for each drug.

Ethnicity and antipsychotic response

OBJECTIVE

To review the data generated by studies examining interethnic/racial differences in response to antipsychotics.

DATA SOURCES

A MEDLINE search (1966-1996) identified all articles examining differences in antipsychotic response among Caucasians, Asians, Hispanics, and African-Americans, as well as articles evaluating postulated mechanisms for these differences.

STUDY SELECTION

All abstracts, studies, and review articles were evaluated.

DATA SYNTHESIS

Ethnic/racial differences in response to antipsychotic medications have been reported and may be due to genetics, kinetic variations, dietary or environmental factors, or variations in the prescribing practices of clinicians. Studies suggest that Asians may respond to lower doses of antipsychotics due to pharmacokinetic and pharmacodynamic differences. Research relevant to African-Americans is limited, but some studies suggest that differences in this group may be due to clinician biases and prescribing practices, rather than to pharmacokinetic or pharmacodynamic variability.

CONCLUSIONS

Future research directed at validating the hypotheses that different ethnic/racial groups show variations in response to antipsychotics should focus on homogeneous ethnic groups, use recent advances in pharmacogenetic testing, and control for such variables as observer bias, gender, disease chronicity, dietary and environmental factors, and exposure to enzyme-inducing and -inhibiting agents. Clinicians should be aware that potential interethnic/racial differences in pharmacodynamics and pharmacokinetics may exist that can alter response to antipsychotics.

Age and cytochrome P450-linked drug metabolism in humans: an analysis of 226 subjects with equal histopathologic conditions

OBJECTIVES

The effect of aging on drug metabolism in humans has not yet been completely described.

METHODS

Two hundred twenty-six patients with equal histopathologic conditions were investigated. The cytochrome P450 contents in the liver biopsy samples, the plasma antipyrine clearance rates after oral administration and, as an independent control of vitality, serum testosterone levels were determined.

RESULTS

Cytochrome P450 content in subjects from 20 to 29 years of age was 7.2 +/- 2.6 nmol.gm-1, increased during the fourth decade (+7.2%, p = NS), declined after 40 years (-16%, p < 0.01) to a level that remained unaltered up to 69 years, and declined further after 70 years (-32%, p < 0.001). The antipyrine (phenazone) clearance rate in young subjects was 46.4 +/- 18.5 ml.min-1, remained unaltered during the fourth decade, and declined after 40 years by a rate of 0.34 ml.min-1 per year toward old age (-29%, p < 0.001). The half-life in young subjects was 9.5 +/- 2.0 hours and increased after 30 years toward old age (+26%, p < 0.001). The volume of antipyrine distribution, 0.46 +/- 0.12 L.kg-1 in young subjects, decreased after 30 years (-11%). In line with the testosterone content, the decrease in drug metabolism was equal in both sexes.

CONCLUSION

This study shows a reduction of in vitro and in vivo drug metabolism with age in humans. The data suggest that at least three age groups--young, middle-aged, and elderly--should be included in the evaluation of the pharmacokinetics of a new drug. The reduction of drug metabolism (-30%) after 70 years of age indicates that care is needed in the prescription of drugs for elderly subjects.

Pharmacokinetics, metabolism and interactions of acid pump inhibitors. Focus on omeprazole, lansoprazole and pantoprazole

This review updates and evaluates the currently available information regarding the pharmacokinetics, metabolism and interactions of the acid pump inhibitors omeprazole, lansoprazole and pantoprazole. Differences and similarities between the compounds are discussed. Omeprazole, lansoprazole and pantoprazole are all mainly metabolished by the polymorphically expressed cytochrome P450 (CYP) isoform S-mephenytoin hydroxylase (CYP2C19), which means that within a population a few individuals (3% of Caucasians) metabolise the compounds slowly compared with the majority of the population. For all 3 compounds, the area under the plasma concentration-versus-time curve (AUC) for a slow metaboliser is, in general, approximately 5 times higher than that in an average patient. Since all 3 compounds are considered safe and well tolerated, and no dosage-related adverse drug reactions have been identified, this finding seems to be of no clinical relevance. The acid pump inhibitors seem to be similarly handled in the elderly, where a somewhat slower elimination can be demonstrated compared with young individuals. In patients with renal insufficiency, omeprazole is eliminated as in healthy individuals, whereas the data on lansoprazole and pantoprazole are unresolved. In patients with hepatic insufficiency, as expected, the elimination rates of all 3 compounds are substantially decreased. No clinically relevant effects on specific endogenous glandular functions, such as the adrenal (cortisol), the gonads or the thyroid, were demonstrated for omeprazole and pantoprazole, whereas a few minor concerns have been raised regarding lansoprazole. The absorption of some compounds, e.g. digoxin, might be altered as a result of the increased gastric pH obtained during treatment with acid pump inhibitors, and, accordingly, similar effects are expected irrespective of which acid pump inhibitor is given. The effect of the acid pump inhibitors on enzymes in the liver has been intensely debated, and some authors have claimed that lansoprazole and pantoprazole have less potential than omeprazole to interact with other drugs metabolised by CYP. However, after assessment of available data in this area, the conclusion is that all 3 acid pump inhibitors have a very limited potential for drug interactions at the CYP level. In addition, the small effects on CYP reported for these compounds are rarely of any clinical relevance, considering the normal intra- (and inter-)individual variations in metabolism observed for most drugs. In conclusion, omeprazole, lansoprazole and pantoprazole are structurally very similar, and an evaluation of available data indicates that also with respect to pharmacokinetics, metabolism and interactions in general they demonstrate very similar properties, even though omeprazole has been more thoroughly studied with regard to different effects.