Assessing the adverse effects of antimuscarinic drugs in older patients: which way forward?

A predictive in vitro model of the impact of drugs with anticholinergic properties on human neuronal and astrocytic systems

The link between off-target anticholinergic effects of medications and acute cognitive impairment in older adults requires urgent investigation. We aimed to determine whether a relevant in vitro model may aid the identification of anticholinergic responses to drugs and the prediction of anticholinergic risk during polypharmacy. In this preliminary study we employed a co-culture of human-derived neurons and astrocytes (NT2.N/A) derived from the NT2 cell line. NT2.N/A cells possess much of the functionality of mature neurons and astrocytes, key cholinergic phenotypic markers and muscarinic acetylcholine receptors (mAChRs). The cholinergic response of NT2 astrocytes to the mAChR agonist oxotremorine was examined using the fluorescent dye fluo-4 to quantitate increases in intracellular calcium [Ca2+]i. Inhibition of this response by drugs classified as severe (dicycloverine, amitriptyline), moderate (cyclobenzaprine) and possible (cimetidine) on the Anticholinergic Cognitive Burden (ACB) scale, was examined after exposure to individual and pairs of compounds. Individually, dicycloverine had the most significant effect regarding inhibition of the astrocytic cholinergic response to oxotremorine, followed by amitriptyline then cyclobenzaprine and cimetidine, in agreement with the ACB scale. In combination, dicycloverine with cyclobenzaprine had the most significant effect, followed by dicycloverine with amitriptyline. The order of potency of the drugs in combination frequently disagreed with predicted ACB scores derived from summation of the individual drug scores, suggesting current scales may underestimate the effect of polypharmacy. Overall, this NT2.N/A model may be appropriate for further investigation of adverse anticholinergic effects of multiple medications, in order to inform clinical choices of suitable drug use in the elderly.

Associations between different measures of anticholinergic drug exposure and Barthel Index in older hospitalized patients

OBJECTIVE

To compare associations between four measures of anticholinergic exposure (anticholinergic risk scale, ARS; anticholinergic drug burden, DBAC; number and use versus no use of anticholinergic drugs), Barthel Index (BI, physical function) and Abbreviated Mental Test (AMT, cognitive function) on admission in older hospitalized patients.

METHODS

Prospective observational study of a consecutive series of 271 older patients (age 83 ± 7 years) from community-dwelling and institutionalized settings, admitted to an acute geriatric admission unit between 28 September 2011 and 18 December 2011. The main outcome measures were BI quartiles (primary outcome) and AMT (secondary outcome) on admission.

RESULTS

Anticholinergic prevalence was 47%. Multinomial logistic regression showed higher DBAC was associated with a greater risk of being in the lower BI quartiles versus highest BI quartile (Q4). This risk was significant for Q3 (p = 0.04) and Q2 (p = 0.02) but not for Q1 (p = 0.06). A greater number of anticholinergic drugs was associated with a higher risk of being in Q2 (p = 0.02). This risk was not significant for either Q3 (p = 0.10) or Q1 (p = 0.06). No significant associations were observed either with use of anticholinergic medication or with ARS and BI quartiles. AMT did not show independent associations with any of the four measures of anticholinergic exposure.

CONCLUSION

In older hospitalized patients, DBAC and some crude measures of anticholinergic exposure, but not ARS, showed independent associations with lower BI, but not AMT. These results highlight differences between various measures of anticholinergic drug exposure when studying their associations with functional status.

Measures of anticholinergic drug exposure, serum anticholinergic activity, and all-cause postdischarge mortality in older hospitalized patients with hip fractures

OBJECTIVES

To assess possible associations between anticholinergic drug exposure and serum anticholinergic activity (SAA) and their capacities to predict all-cause mortality in older hospitalized patients.

SETTING

Academic medical center.

PARTICIPANTS AND MEASUREMENTS

Data on clinical characteristics, full medication exposure, SAA, and 4 anticholinergic drug scoring systems (ADSSs: Anticholinergic Risk Scale [ARS], Anticholinergic Drug Scale, Anticholinergic Burden scale, and anticholinergic component of the Drug Burden Index) were collected in 71 older hospitalized patients (age 84 ± 6 years) awaiting surgical repair after hip fractures.

RESULTS

The median (range) SAA was 2.8 (1.1-4.9) pmol/mL. Age (ρ = 0.25, p = 0.03), Katz Index of Independence in Activities of Daily Living score (ρ = 0.39, p = 0.001), in-hospital delirium (ρ = 0.29, p = 0.01), preadmission cognitive impairment (ρ = 0.31, p = 0.01), and the number of nonanticholinergic drugs (n-NA, ρ = -0.27, p = 0.02) were associated with SAA. No significant associations were detected between ADSSs and SAA. Cognitive impairment (β = 2.1, 95% confidence interval [CI]: 0.7 to 2.5, p = 0.005) and n-NA (β = -0.3, 95% CI: -0.5 to -0.03, p = 0.03) were independently associated with SAA. Cognitive impairment (hazard ratio [HR]: 6.7, 95% CI: 1.1 to 40.3, p = 0.04) and higher ARS scores (HR: 2.2, 95% CI: 1.2 to 3.7, p = 0.006) independently predicted 3-month mortality whereas in-hospital delirium (HR: 3.6, 95% CI: 1.3 to 10.3, p = 0.02), living at home (HR: 0.2, 95% CI: 0.0 to 0.9, p = 0.03), and length of hospital stay (HR: 1.1, 95% CI: 1.0 to 1.2, p = 0.004) independently predicted 1-year mortality after adjustment for age, gender, and Charlson comorbidity index.

CONCLUSIONS

Cognitive impairment and n-NA, but not ADSSs, are independently associated with SAA in older hospitalized patients. The ARS score, together with cognitive impairment, in-hospital delirium, place of residence, and length of hospital stay, predicts all-cause mortality in this group.

Predicting and detecting adverse drug reactions in old age: challenges and opportunities

Increased, often inappropriate, drug exposure, pharmacokinetic and pharmacodynamic changes, reduced homeostatic reserve and frailty increase the risk of adverse drug reactions (ADRs) in the older population, thereby imposing a significant public health burden. Predicting and diagnosing ADRs in old age presents significant challenges for the clinician, even when specific risk scoring systems are available. The picture is further compounded by the potential adverse impact of several drugs on more 'global' health indicators, for example, physical function and independence, and the fragmentation of care (e.g., increased number of treating doctors and care transitions) experienced by older patients during their clinical journey. The current knowledge of drug safety in old age is also curtailed by the lack of efficacy and safety data from pre-marketing studies. Moreover, little consideration is given to individual patients' experiences and reporting of specific ADRs, particularly in the presence of cognitive impairment. Pending additional data on these issues, the close review and monitoring of individual patients' drug prescribing, clinical status and biochemical parameters remain essential to predict and detect ADRs in old age. Recently developed strategies, for example, medication reconciliation and trigger tool methodology, have the potential for ADRs risk mitigation in this population. However, more information is required on their efficacy and applicability in different healthcare settings.