Anticholinergic burden and antihistamine exposure

Follow the ingredient across the product labels

An antihistamine can appear as an allergy medicine, a nighttime product or an ingredient in a combination preparation. The therapeutic label on the package does not change the ingredient’s identity. A medication review should therefore collect the full product list and identify duplicate or overlapping ingredients before interpreting exposure.

Nonprescription availability can make these products easier to overlook in a routine medication history. It does not establish that every formulation is appropriate for every older adult. The medication-reconciliation approach is useful here because it asks what is actually used, not only what appears among current prescriptions.

A class label is a starting point, not a completed comparison

Antihistamines are often discussed in broad groups, including first- and later-generation agents. Those labels can orient a discussion, but they do not supply a source-native score for every ingredient. A profile should show the medication’s actual observations rather than inherit a value from its group.

The AGS first-generation-antihistamine criterion provides geriatric context for identified medicines and uses. Its source qualifications should be retained. A class concern does not mean every product has been studied under identical conditions or that the clinical effect is the same in every person.

Three preserved records illustrate different evidence patterns

Diphenhydramine shows agreement at value 3 across its seven public source versions. Loratadine shows value 1 across its seven public observations. Cetirizine shows a wider spread: BAAS 2019 and JARS 2025 publish 2, several other represented sources publish 1, and Yamada ABS 2023 publishes an explicit zero. These are directly inspectable source observations.

The patterns should be described without turning them into a universal ranking of clinical safety. An ordinal category is not a probability of sedation, a measurement of receptor occupancy or a treatment recommendation. Matching categories also do not prove equal benefit for the condition being treated.

Cetirizine is particularly useful for understanding why disagreement should remain visible. The zero is a real source finding, not a missing entry. The nonzero values belong to other methods. Averaging them would create a result none of the sources published and obscure the reason the comparison is informative.

Actual use matters more than the package’s presence

An occasional product, a seasonal course and regular use are different exposure histories. A medication list that records only the ingredient does not tell the reviewer which history applies. Ask how often it was taken during the period relevant to the clinical concern.

Combination products need a full ingredient review. A person may recognize the product’s main purpose without knowing that another ingredient overlaps with a separate medicine. Conversely, apparent duplication should be confirmed before assuming that two entries represent two exposures.

Route and formulation should also remain attached. A source statement about a particular route should not be generalized to every preparation. If the source itself is nonspecific, that limitation should be stated rather than completed by assumption.

Keep medication-specific outcome evidence in context

The prospective study of diphenhydramine in hospitalized older patients provides evidence about a named drug in an acute-care setting. It supports a focused concern while leaving the study design and population central to interpretation. It is not a direct trial of every antihistamine product used in the community.

Laboratory findings have a different role. The radioreceptor study examined activity under defined conditions. Such evidence can inform a classification, but it does not give a patient-specific estimate of next-day function or future cognition.

The review should use the most relevant evidence for the question being asked. A concern about a symptom after a recent dose requires an exposure timeline. A question about long-term use requires attention to duration and the outcomes actually studied.

What the geriatric tag should explain

A useful tag discussion identifies the criterion and its qualification rather than repeating the same effects paragraph for every ingredient. It should explain why the criterion is relevant to the medication and what additional context, if any, changes the answer.

The selected overlay is not a complete assessment of every antihistamine or every geriatric prescribing issue. A medication outside it is not thereby safe. The source-scale table remains primary for the ordinal observations, while the geriatric information remains a separately attributed clinical layer.

A practical comparison question

Ask which ingredient is being used, for what symptom, by which route and with what benefit or concern. Compare source classifications only after the products are correctly identified. Do not choose a substitute solely by sorting medications from lowest to highest category; therapeutic appropriateness requires information the scale does not contain.

If care changes, assess the original symptom and the adverse-effect concern directly. A smaller category does not prove that the new plan works better, and an unchanged category does not prove that the clinical experience is identical.

The point of the spotlight

Antihistamine review is most informative when it moves from broad class labels to precise ingredients, actual exposure and source-specific findings. The preserved disagreements and limitations are useful evidence, not imperfections to remove by inventing a single reassuring or alarming answer.

References

1. American Geriatrics Society 2023 Updated AGS Beers Criteria for Potentially Inappropriate Medication Use in Older Adults. J Am Geriatr Soc. 2023;71:2052-2081. Source
2. Vennard O, Stewart C, Tolia M, Soiza RL, Myint PK. Anticholinergic Medication Burden Scales: A Systematic Review. J Am Geriatr Soc. 2026;74(6):1771-1784. Source
3. American Geriatrics Society Beers Criteria Alternatives Panel. Alternative Treatments to Selected Medications in the 2023 AGS Beers Criteria. J Am Geriatr Soc. 2025;73:2657-2677. Source
4. Fox C, et al. Effect of medications with anti-cholinergic properties on cognitive function, delirium, physical function and mortality: a systematic review. Age Ageing. 2014;43:604-615. Source
5. Ruxton K, Woodman RJ, Mangoni AA. Drugs with anticholinergic effects and cognitive impairment, falls and all-cause mortality in older adults: a systematic review and meta-analysis. Br J Clin Pharmacol. 2015;80(2):209-220. doi:10.1111/bcp.12617. Source
6. Egberts A, et al. Anticholinergic Drug Burden and Delirium: A Systematic Review. J Am Med Dir Assoc. 2021;22:65-73.e4. Source
7. Agency for Healthcare Research and Quality. Medications at Transitions and Clinical Handoffs (MATCH) Toolkit for Medication Reconciliation. Source
8. UnifiedACB. Preserved public source-observation dataset, v3.0 RC12 final; inspected for this editorial revision. Source
9. Agostini JV, Leo-Summers LS, Inouye SK. Cognitive and other adverse effects of diphenhydramine use in hospitalized older patients. Arch Intern Med. 2001;161:2091–2097. Source
10. Chew ML, et al. Anticholinergic activity of 107 medications commonly used by older adults. J Am Geriatr Soc. 2008;56:1333–1341. Source

Disclosure

Funding: None. Conflict of interest: None declared for the UnifiedACB educational project.

Educational evidence summary. This content does not provide patient-specific medical advice and does not replace clinical judgment, medication reconciliation, or prescribing guidance.