Dimenhydrinate is a type of ethanolamine and a 1st generation antihistamine , antagonizes the action of histamine, with anti-allergic properties. Dimenhydrinate competitively binds to the histamine receptors to block the action of H1 receptors,and hence preventing the histamine to act on the smooth muscles of lungs, bronchioles, capillaries and the smooth muscle of the gastrointestinal tract. In This way it prevents bronchoconstriction induced by histamine, GI smooth muscle spasm, increased capillary permeability and vasodilation.
Dimenhydrinate is also used as an antiemetics drug in a combination which contains theophylline and diphenhydramine. Dimenhydrinate is not as effective in the chemotherapy induced nausea treatment. Dimenhydrinate directly blocks and inhibits the stimulation of various types of nerves in the central nervous system and also in the inner ear to subdue vomiting, vertigo, nausea, and dizziness. Dimenhydrinate and Diphenhydramine both reduce the excitation of the vestibular nerve because of the linear or angular acceleration motions.
In the pediatric population,the use of Dimenhydrinate is apparently safe. There is very little research about the adverse reaction of the drug, Doctors or general practitioners need to diagnose the definite cause of vomiting and nausea before considering the drug if it will be effective or not and also a need to make sure that patients use the medicine safely and prevents the potential drug interaction by checking if the patient taking other drugs.
Dimenhydrinate is an over the counter drug which consists of 44% to 47% 8-chlorotheophylline and 53% to 56% diphenhydramine. The most common indication of dimenhydrinate is vomiting, nausea, or dizziness because of motion sickness, but dimenhydrinate is more commonly used for vomiting and nausea from different types of conditions. The current labeling of Health Canada includes OTC use of this drug for those patients who are older than 2 years of age and use as directed by the general physician in those patients who are younger than 2 years of age. This recommendation of Health Canada is purely based on age and not on weight. Dimenhydrinate is more commonly used by children and parents due to its status as an over-the-counter drug, and it is believed that the drug is safe for use.
Despite the widespread use of dimenhydrinate, proof of having no adverse effects is lacking.There is no sufficient Evidence of dimenhydrinate associated complications. There is no specific data available about the adverse effects of the drug because of lack of reporting by the consumers. Despite of this the data about the overdose of dimenhydrinate has been available to cause the anticholinergic and central nervous system symptoms (eg,tachypnea, confusion, visual hallucinations, slurred speech, ataxia, and mild tachycardia), and also some patient has been presented on toxicity because of its medicinal use.
The AAPCC (American Association of Poison Control Centers) published the guidelines on diphenhydramine and dimenhydrinate poisoning. They are not found to have specific adverse effects at therapeutic dose. All the adverse effects after acute overdose to dimenhydrinate are reported in younger children than 6 years of age.
Another consideration the physician always kept in mind before prescribing dimenhydrinate is the potential drug interaction of dimenhydrinate with other drugs metabolized by the pathway of cytochrome P450. Caffeine is also metabolized through the 1A2 enzyme of the cytochrome P450, and hence it is possible that dimenhydrinate may inhibit or exaggerate the common response of different medicine such as calcium channel blocker,omeprazole, oral contraceptives, olanzapine, diltiazem, and verapamil.
Although there are many different conditions in the children which are associated with vomiting, the use of dimenhydrinate is only recommended if other treatment options are not available.
There are different common conditions present in patients such as vomiting or nausea associated with motion sickness and Acute viral gastroenteritis are more common in children. Oral rehydration therapy is recommended in this case of viral gastroenteritis because it is a self limiting disease and hence dimenhydrinate should not be recommended in that particular case. In the same way patients with severe or chronic illness should be admitted in hospital rather than treatment with dimenhydrinate for intravenous rehydration.
Dimenhydrinate is an OTC drug which is used for antiemetic purposes more commonly.In the last dimenhydrinate is considered to be safe for use in both adult and pediatric populations. It is wise to properly diagnose the cause of vomiting before recommending the dimenhydrinate and should always keep in mind its potential drug interactions before recommending dimenhydrinate.
- Motion sickness
- Spinning sensation (vertigo)
- Radiation sickness
- Vomiting and nausea following surgery
- Known history of hypersensitivity to dimenhydrinate
- Neonates and premature infants
- Breastfeeding mothers
- Diphenhydramine should not be prescribed to alcoholics and to those who are on antidepressant therapy.
- MAO inhibitors intensify and prolong the effects of dimenhydrinate(anticholinergic).
Common Adverse Effects
- Impaired coordination
- Epigastric discomfort
- Thickened bronchial secretions
- Dry mucous membranes
- CNS stimulation, paradoxical
- Urinary retention
- Blurred vision
- Erectile dysfunction
- Early menses
- Anaphylaxis/anaphylactoid reaction
- QT prolongation
- Anemia, hemolytic
- Toxic psychosis
- Labyrinthitis, acute
- Heat stroke
- Dimenhydrinate may cause the postrenal obstruction, which decreases the GFR(glomerular filtration rate) due to the effect of urine retention. If any sign and symptoms of acute or chronic kidney injury appears, immediately discontinue diphenhydramine medicine or therapy and begin symptomatic treatment to support the kidney function if needed.
- Be careful while driving if you are taking dimenhydrinate therapy for the long term because it depresses the central nervous system activity .
- Don’t use dimenhydrinate if you are alcoholic or taking sedatives because dimenhydrinate potentiates their effects.
- Don’t give dimenhydrinate to elderly patients due to the danger of falling because it causes dizziness and hypotension.
- Dimenhydrinate causes the prolongation of the QTc interval blocking the sodium channels which are fast and by repolarizing the potassium channels and hence use with caution in cardiac patients.
- Use with caution in patients with cardiac problems, hyperthyroidism, asthma, increased ocular pressure, and hypertension.
High Risk Groups
- Patients who are allergic to dimenhydrinate
- Pregnant ladies
- Patients with Known history of cardiac, kidney, and liver problem.