{"id":230,"date":"2019-11-12T17:22:48","date_gmt":"2019-11-12T22:22:48","guid":{"rendered":"https:\/\/opentextbc.ca\/nursingpharmacology\/chapter\/5-6-antihistamines\/"},"modified":"2023-08-15T12:56:35","modified_gmt":"2023-08-15T16:56:35","slug":"5-6-antihistamines","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/nursingpharmacology\/chapter\/5-6-antihistamines\/","title":{"raw":"5.6 Antihistamines","rendered":"5.6 Antihistamines"},"content":{"raw":"

Antihistamines<\/h1>\r\nDiphenhydramine and Cetirizine are two commonly-seen antihistamine drugs. In this chapter we explore Diphenhydramine.\r\n\r\nDiphenhydramine is an example of a first-generation antihistamine. (See Figures 5.6a[footnote]\"Benadryl Allergy USA<\/a>\" by ZenBenjamin<\/a> is licensed under CC BY-NC-SA 2.0<\/a>[\/footnote] and 5.6b.[footnote]\"diphenhydramine (1)<\/a>\" by Intropin<\/a> is licensed under CC BY-NC 2.0[\/footnote]<\/a>)\u00a0 Second-generation antihistamines were developed to have fewer side effects. An example of a second-generation antihistamine is cetirizine.\r\n\r\n[caption id=\"attachment_227\" align=\"aligncenter\" width=\"339\"]\"An Figure 5.6a Diphenhydramine is a first-generation antihistamine that is available orally or as an IV medication[\/caption]\r\n\r\n[caption id=\"attachment_228\" align=\"aligncenter\" width=\"259\"]\"A Figure 5.6b Diphenhydramine HCl preparation, single dose vial for IV administration[\/caption]\r\n

Mechanism of Action<\/h2>\r\nAntihistamines have the following mechanisms of action: blocks histamine at H1 receptors; inhibits smooth muscle constriction in blood vessels and the respiratory and GI tracts; and decreases capillary permeability, salivation, and tear formation.\r\n

Indications for Use<\/h2>\r\nAntihistamines are used for relief of allergy or cold symptoms.\r\n

Nursing Considerations Across the Lifespan<\/h2>\r\nThis medication is not safe for children under the age of 2 years without a healthcare provider's order.\r\n

Adverse\/Side Effects<\/h2>\r\nFirst-generation medications can cause anticholinergic effects (such as dry mouth, urinary retention, constipation and blurred vision). CNS depression or CNS stimulation with excessive doses can occur, especially in children. Therefore, first-generation antihistamines should be used with caution in the elderly.\r\n\r\nSecond-generation medications may cause headache, nausea, vomiting, dysmenorrhea, and fatigue.[footnote]Frandsen, G. & Pennington, S. (2018). Abrams\u2019 clinical drug: Rationales for nursing practice <\/em>(11th ed.). Wolters Kluwer.[\/footnote]\r\n

Client Teaching & Education<\/h2>\r\nClients should be advised that antihistamines may cause drowsiness, and concurrent use of alcohol or other CNS depressants should be avoided.\u00a0 Clients should take only the recommended amount of medication and not exceed dosing recommendations.\u00a0 Some clients may experience side effects such as dry mouth, and frequent oral hygiene may assist in alleviating discomfort.[footnote]uCentral from Unbound Medicine. https:\/\/www.unboundmedicine.com\/ucentral<\/a>[\/footnote]\r\n

Diphenhydramine Medication Card<\/h1>\r\nNow let's take a closer look at the medication card for diphenhydramine and cetirizine in Table 5.6.[footnote]This work is a derivative of Pharmacology Notes: Nursing Implications for Clinical Practice<\/a> by Gloria Velarde<\/a> licensed under CC BY-NC-SA 4.0<\/a>.[\/footnote], [footnote]Frandsen, G. & Pennington, S. (2018). Abrams\u2019 clinical drug: Rationales for nursing practice <\/em>(11th ed.). Wolters Kluwer.[\/footnote], [footnote]This work is a derivative of Daily Med<\/a> by U.S. National Library of Medicine<\/a> in the public domain<\/a>. [\/footnote] Medication cards are intended to assist students to learn key points about each medication class.\u00a0 Basic information related to a common generic medication in this class is outlined, including administration considerations, therapeutic effects, and side effects\/adverse effects.\u00a0 Prototype\/generic medication listed in the medication card is also hyperlinked to a free resource from\u00a0 Daily Med<\/a>.\u00a0 Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.\r\n
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Medication Card 5.6.1: Diphenhydramine<\/h2>\r\n<\/header>\r\n
\r\n\r\nClass: <\/strong>Antihistamines (first generation)\r\n\r\nPrototypes: <\/strong>Diphenhydramine (Benadryl)\r\n\r\nMechanism: <\/strong>Blocks histamine at H1 receptor, inhibits smooth muscle constriction in blood vessels and respiratory and GI tracts: decreases capillary permeability, salivation and tear formation\r\n

Therapeutic Effects<\/h3>\r\n