Dangers of non sedating antihistamine
In addition to causing significant patient harm, the use of anticholinergic medications in older nursing home patients negatively impacts Centers for Medicare & Medicaid Services quality measures, such as the use of high-risk antipsychotic medications, the percentage of patients with a decline in their ability to perform activities of daily living, the percentage of patients with falls and serious injury, and urinary tract infection rates.
Regardless of practice setting, healthcare professionals should take steps to increase the awareness of side effects associated with first-generation antihistamines.
First-generation antihistamines are widely available without a prescription and commonly used to treat allergic symptoms, including rhinitis, conjunctivitis, pruritus, eczema, urticaria, and anaphylactic reactions.
These antihistamines are more selective on peripheral H1 receptors and have a lower affinity for cholinergic and alpha-adrenergic receptor sites, which reduces the risk of anticholinergic and central nervous system side effects.
Older adults are especially sensitive to the central nervous system- and anticholinergic-related side effects of sedating antihistamines because of decreased cholinergic neurons or receptors in the brain, reduced hepatic and renal function, and increased blood-brain permeability.
These antihistamines also are potent muscarinic receptor antagonists that can lead to serious anticholinergic side effects, such as sinus tachycardia, dry skin, dry mucous membranes, dilated pupils, constipation, ileus, urinary retention, and agitated delirium.3 The mnemonic “blind as a bat, dry as a bone, red as a beet, mad as a hatter, and hot as a hare” often is used to help describe and identify patients suffering from anticholinergic syndrome (see Table 2 below).
Urinary retention and difficulty urinating can be particularly troublesome in male patients with enlarged prostates, and this retention can increase the risk of urinary tract infections, especially in women.4 The second-generation nonsedating antihistamines generally are considered as safer alternatives for use in older adults who require treatment for allergic rhinitis and other allergy symptoms.
6 Antihistamine medications block or reduce histamine-mediated effects at one of four identified histamine receptors (see Table 1 below).