Dimenhydrinate

INTRODUCTION

Indications

Nausea, vomiting, dizziness, and vertigo accompanying motion sickness.

Action

Inhibits vestibular stimulation. Has significant CNS depressant, anticholinergic, antihistaminic, and antiemetic properties. Therapeutic Effects: Decreased vestibular stimulation, which may prevent motion sickness.

Adverse Reactions/Side Effects

CNS: drowsiness, dizziness, headache, paradoxical excitation (children). EENT: blurred vision, tinnitus. CV: hypotension, palpitations. GI: anorexia, constipation, diarrhea, dry mouth. GU: dysuria, frequency. Derm: photosensitivity. Local: pain at IM site.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Assess blood pressure periodically, and compare to normal values (see Appendix F). Report a sustained or symptomatic decrease in blood pressure (hypotension) or other cardiac symptoms (palpitations).

• Watch for signs of increased excitation and hyperactivity in children. Severe or problematic excitation may require a change in dose or drug.

• Monitor any improvements in symptoms (nausea, vomiting, dizziness, vertigo) to help document the effects of this drug.

• 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 IM injection site for excessive or prolonged pain and swelling.

Interventions

• 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).

• In patients with chronic vestibular problems, implement therapeutic exercises and vestibular training activities to help reduce symptoms.

• Causes photosensitivity; use care if administering UV treatments. Advise patient to avoid direct sunlight and use sunscreens and protective clothing.

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 bothersome side effects including severe or prolonged headache blurred vision, buzzing/ringing in the ears (tinnitus), problems with urination, or GI problems (constipation, diarrhea, dry mouth, loss of appetite).

Pharmacokinetics

Absorption: Well absorbed after oral or IM administration.

Distribution: Probably crosses the placenta and enters breast milk.

Metabolism and Excretion: Metabolized by the liver.

Half-life: Unknown.