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clemastine (klem-as-teen)

Dayhist Allergy, Tavist Allergy


Therapeutic: allergy, cold, and cough remedies, antihistamines


Relief of allergic symptoms caused by histamine release, including Allergic rhinitis, Urticaria.


Antagonizes the effects of histamine at H1 receptor sites; does not bind to or inactivate histamine. Therapeutic Effects: Decreased symptoms of histamine excess (sneezing, rhinorrhea, nasal and ocular pruritus, ocular tearing, and redness).

Adverse Reactions/Side Effects

CNS: drowsiness, confusion, dizziness, paradoxical excitation (children). EENT: blurred vision. CV: hypertension, arrhythmias, hypotension, palpitations, tachycardia. GI: dry mouth, constipation, nausea, obstruction, vomiting. GU: urinary retention. Derm: rash. Resp: thick mucus.


Examination and Evaluation

  • Assess blood pressure (BP) and compare to normal values (See Appendix F). Report changes in BP, either a problematic decrease in BP (hypotension) or a sustained increase in BP (hypertension).

  • Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report any rhythm disturbances or symptoms of increased arrhythmias, including palpitations, chest discomfort, shortness of breath, fainting, and fatigue/weakness.

  • Monitor symptoms of allergic rhinitis (sneezing, rhinitis, itching eyes, cough) or urticaria (rash, hives, itching) to help document benefits of this drug in treating these disorders.

  • Assess dizziness and drowsiness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

  • Assess confusion or other alterations in cognitive function (See Appendix D). Notify the physician if these symptoms become problematic.

  • Monitor signs of increased excitation in children. Severe or problematic excitation may require a change in dose or drug.


  • Guard against falls and trauma (hip fractures, head injury, and so forth). Implement fall-prevention strategies, especially in older adults or if balance is impaired (See Appendix E).

  • Because of an increased risk of arrhythmias and abnormal BP responses, use caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

Patient/Client-Related Instruction

  • Advise patient about the risk of daytime drowsiness and decreased attention and mental focus. These problems can be severe in certain people. Use care if driving or in other activities that require quick reactions and strong concentration.

  • Advise patient to avoid alcohol and other CNS depressants because of the increased risk of sedation and adverse effects.

  • Instruct patient to report other troublesome side effects, including severe or prolonged skin rash, blurred vision, thickened mucus, urinary retention, or GI problems (nausea, vomiting, constipation, dry mouth).

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