Dimenhydrinate MCQs With Answer is a focused study tool for B.Pharm students covering the antiemetic and antihistamine drug dimenhydrinate. This introduction and question set emphasize key concepts: chemical composition (diphenhydramine + 8‑chlorotheophylline), mechanism of action as a first‑generation H1 receptor antagonist with anticholinergic effects, pharmacokinetics (absorption, hepatic metabolism, renal excretion), therapeutic uses (motion sickness, vertigo, nausea), dosing, adverse effects (sedation, dry mouth, urinary retention), drug interactions, contraindications, and counseling points. Questions are designed to deepen understanding for exam preparation and clinical application. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the chemical composition of dimenhydrinate?
- Diphenhydramine combined with 8‑chlorotheophylline
- Promethazine combined with caffeine
- Cyclizine combined with theophylline
- Meclizine combined with atropine
Correct Answer: Diphenhydramine combined with 8‑chlorotheophylline
Q2. Which best describes the primary mechanism of action of dimenhydrinate?
- Selective H2 receptor agonist
- H1 receptor antagonist with anticholinergic properties
- Dopamine D2 receptor blocker
- 5‑HT3 receptor antagonist
Correct Answer: H1 receptor antagonist with anticholinergic properties
Q3. What is the main clinical indication for dimenhydrinate?
- Chronic asthma management
- Motion sickness and vestibular nausea
- Treatment of peptic ulcer disease
- Chronic insomnia
Correct Answer: Motion sickness and vestibular nausea
Q4. What is the role of 8‑chlorotheophylline in dimenhydrinate?
- Potentiates anticholinergic side effects
- Acts as an antiemetic by blocking 5‑HT3 receptors
- Stimulant component that partly counteracts sedation
- Prodrug converted to diphenhydramine in vivo
Correct Answer: Stimulant component that partly counteracts sedation
Q5. To which pharmacological class does dimenhydrinate belong?
- Second‑generation H1 antihistamine
- First‑generation H1 antihistamine
- Anticholinesterase inhibitor
- Benzodiazepine class
Correct Answer: First‑generation H1 antihistamine
Q6. Which is the most common adverse effect experienced with dimenhydrinate?
- Severe hypertension
- Profound diuresis
- Drowsiness and sedation
- Hypoglycemia
Correct Answer: Drowsiness and sedation
Q7. Dimenhydrinate is contraindicated in which condition?
- Open‑angle glaucoma
- Narrow‑angle glaucoma
- Hypothyroidism
- Hyperlipidemia
Correct Answer: Narrow‑angle glaucoma
Q8. Which routes of administration are available for dimenhydrinate?
- Oral, rectal (suppository), intramuscular and intravenous
- Topical and transdermal patch only
- Inhalation aerosol only
- Sublingual tablet only
Correct Answer: Oral, rectal (suppository), intramuscular and intravenous
Q9. What is the usual single adult oral dose of dimenhydrinate for motion sickness?
- 5–10 mg
- 50–100 mg
- 500–1000 mg
- 0.5–1 mg
Correct Answer: 50–100 mg
Q10. What is the commonly cited maximum daily dose for adults of dimenhydrinate?
- 100 mg/day
- 400 mg/day
- 1500 mg/day
- 10 mg/day
Correct Answer: 400 mg/day
Q11. What pediatric dose range is typically recommended for small children (2–6 years)?
- 12.5–25 mg
- 100–200 mg
- 1–2 mg
- 75–150 mg
Correct Answer: 12.5–25 mg
Q12. What is the usual onset of action after oral administration?
- 15–30 minutes
- 6–8 hours
- 24–48 hours
- Instantaneous
Correct Answer: 15–30 minutes
Q13. How long does the antiemetic effect of dimenhydrinate typically last?
- 4–6 hours
- 12–24 hours
- Less than 5 minutes
- Several days
Correct Answer: 4–6 hours
Q14. What is the major route of metabolism for dimenhydrinate’s active moiety?
- Hepatic metabolism
- Excreted unchanged in feces
- Metabolized by plasma esterases only
- Not metabolized at all
Correct Answer: Hepatic metabolism
Q15. How are dimenhydrinate metabolites primarily eliminated?
- Renal excretion
- Exhalation via lungs
- Secretion in bile only with no renal role
- Stored in adipose tissue indefinitely
Correct Answer: Renal excretion
Q16. Co‑administration of dimenhydrinate with alcohol leads to:
- Reduced sedation compared with dimenhydrinate alone
- Increased CNS depression and sedation
- No interaction; effects are unchanged
- Complete reversal of anticholinergic effects
Correct Answer: Increased CNS depression and sedation
Q17. Overdose of dimenhydrinate most commonly produces which clinical picture?
- Cholinergic crisis with sweating and miosis
- Anticholinergic syndrome: agitation, dry skin, mydriasis
- Profound hypoglycemia and bradycardia
- Respiratory depression only with no other features
Correct Answer: Anticholinergic syndrome: agitation, dry skin, mydriasis
Q18. What is the recommended approach to using dimenhydrinate in pregnancy?
- Contraindicated in all trimesters
- Use with caution; only if benefits outweigh risks
- High‑dose therapy is recommended for all pregnant women
- Safe without restriction at any dose
Correct Answer: Use with caution; only if benefits outweigh risks
Q19. Which paradoxical effect may occur in children given dimenhydrinate?
- Profound sedation in all cases
- Paradoxical excitation and hyperactivity
- Permanent hearing loss
- Immediate renal failure
Correct Answer: Paradoxical excitation and hyperactivity
Q20. Combining dimenhydrinate with MAO inhibitors may result in:
- Reduced anticholinergic effects
- Potentiation of anticholinergic and CNS effects
- Complete inactivation of dimenhydrinate
- No interaction at all
Correct Answer: Potentiation of anticholinergic and CNS effects
Q21. The antiemetic action of dimenhydrinate is primarily due to blockade of which pathway?
- Gastric acid secretion pathway
- H1 receptors in the vestibular system and central vomiting center
- Renin‑angiotensin system
- Peripheral serotonin receptors in the gut only
Correct Answer: H1 receptors in the vestibular system and central vomiting center
Q22. Dimenhydrinate availability status in many countries is:
- Prescription only everywhere
- Over‑the‑counter (OTC) in many formulations
- Banned worldwide
- Only available as a hospital injectable
Correct Answer: Over‑the‑counter (OTC) in many formulations
Q23. Which adverse effect is attributable to dimenhydrinate’s anticholinergic action?
- Excessive lacrimation (tearing)
- Urinary retention
- Hypersalivation
- Bradycardia with increased secretions
Correct Answer: Urinary retention
Q24. What special precaution is advised when prescribing dimenhydrinate to elderly patients?
- No dose adjustment; elderly tolerate it best
- Use lower doses or avoid due to increased anticholinergic sensitivity
- Double the dose because of decreased absorption
- Combine with other anticholinergics for better effect
Correct Answer: Use lower doses or avoid due to increased anticholinergic sensitivity
Q25. 8‑Chlorotheophylline belongs to which chemical class?
- Benzodiazepine derivative
- Methylxanthine derivative
- Opioid alkaloid
- Steroid nucleus compound
Correct Answer: Methylxanthine derivative
Q26. Pharmacologically, dimenhydrinate is best described as:
- A single pure compound unrelated to diphenhydramine
- A salt complex of diphenhydramine and a methylxanthine
- A combination of promethazine and metoclopramide
- A nitroimidazole antibiotic
Correct Answer: A salt complex of diphenhydramine and a methylxanthine
Q27. Which sign is NOT typical of dimenhydrinate overdose?
- Mydriasis (dilated pupils)
- Dry, flushed skin
- Miosis (pinpoint pupils)
- Hallucinations and agitation
Correct Answer: Miosis (pinpoint pupils)
Q28. For prevention of motion sickness, when is dimenhydrinate optimally administered?
- 30 minutes to 1 hour before travel
- Only after symptoms start
- At least 24 hours before travel
- Never before travel; useful only post‑exposure
Correct Answer: 30 minutes to 1 hour before travel
Q29. In a patient with benign prostatic hyperplasia (BPH), dimenhydrinate should be:
- Used freely with no concern
- Avoided or used with caution due to risk of urinary retention
- Prescribed at very high doses to overcome obstruction
- Replaced by another anticholinergic
Correct Answer: Avoided or used with caution due to risk of urinary retention
Q30. What clinical monitoring is most important after initiating dimenhydrinate therapy?
- Regular liver enzyme panels daily
- Monitor for excessive sedation, anticholinergic effects and urinary retention
- Continuous ECG monitoring in all patients
- No monitoring or counseling is ever required
Correct Answer: Monitor for excessive sedation, anticholinergic effects and urinary retention
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com