Codeine MCQs With Answer

Codeine MCQs With Answer provide B. Pharm students a focused, exam-oriented review of one of the most commonly used opioid analgesics. This concise, keyword-rich introduction covers codeine’s pharmacology, mechanism of action, metabolism (notably CYP2D6 conversion to morphine), therapeutic uses including analgesia and antitussive effects, adverse reactions, dosing, drug interactions, and regulatory aspects. These practice questions are designed to reinforce clinical reasoning, safe dispensing, and patient counseling skills essential for pharmacy practice. Each question emphasizes core concepts, metabolism, toxicity management, and formulation differences to deepen understanding beyond rote memorization. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary mechanism of action of codeine?

• Inhibition of cyclooxygenase enzymes
• Agonism at mu-opioid receptors
• Blocking NMDA receptors
• Enhancing GABAergic transmission

Correct Answer: Agonism at mu-opioid receptors

Q2. Codeine is primarily metabolized to which active metabolite responsible for most of its analgesic effect?

• Norcodeine
• Morphine
• Hydrocodone
• Codeine-6-glucuronide

Correct Answer: Morphine

Q3. Which hepatic enzyme is mainly responsible for converting codeine to morphine?

• CYP3A4
• CYP1A2
• CYP2D6
• CYP2C19

Correct Answer: CYP2D6

Q4. A patient who is an ultra-rapid metabolizer of CYP2D6 taking codeine is at increased risk of:

• Reduced analgesia due to poor conversion
• Excessive sedation and respiratory depression
• Enhanced anti-inflammatory effects
• Renal toxicity

Correct Answer: Excessive sedation and respiratory depression

Q5. Common adverse effects of codeine include all EXCEPT:

• Constipation
• Respiratory depression
• Bradycardia
• Itching (pruritus)

Correct Answer: Bradycardia

Q6. Codeine is classified pharmacologically as a:

• Nonsteroidal anti-inflammatory drug
• Weak opioid agonist
• Pure opioid antagonist
• Synthetic cannabinoid

Correct Answer: Weak opioid agonist

Q7. Which formulation is commonly combined with codeine for analgesia in over-the-counter or prescription products?

• Aspirin
• Paracetamol (acetaminophen)
• Ibuprofen only
• Amoxicillin

Correct Answer: Paracetamol (acetaminophen)

Q8. Codeine’s antitussive effect is primarily mediated by action at:

• Peripheral nociceptors
• Medullary cough center in the brainstem
• Bronchial smooth muscle receptors
• Histamine H1 receptors

Correct Answer: Medullary cough center in the brainstem

Q9. Which of the following populations is at highest risk and should generally avoid codeine?

• Young adults aged 25–40
• Breastfeeding mothers and neonates
• Patients with hypertension
• Patients with mild osteoarthritis

Correct Answer: Breastfeeding mothers and neonates

Q10. The onset of analgesic action after oral administration of codeine is approximately:

• 5–10 minutes
• 30–60 minutes
• 4–6 hours
• 24 hours

Correct Answer: 30–60 minutes

Q11. Which pharmacokinetic property explains the variation in plasma morphine concentration after codeine dosing?

• First-pass hepatic metabolism by CYP2D6
• Absorption in the stomach independent of enzymes
• Renal reabsorption by transporter proteins
• Rapid conjugation by glutathione

Correct Answer: First-pass hepatic metabolism by CYP2D6

Q12. Codeine is commonly scheduled under controlled substances regulations because of its:

• Antipyretic effect
• Potential for abuse and dependence
• High risk of hepatotoxicity
• Antibiotic resistance concerns

Correct Answer: Potential for abuse and dependence

Q13. A major metabolic pathway of codeine besides O-demethylation to morphine is:

• N-acetylation
• O-glucuronidation to codeine-6-glucuronide
• Sulfation of the aromatic ring
• Methylation to form thebaine

Correct Answer: O-glucuronidation to codeine-6-glucuronide

Q14. In case of codeine overdose with respiratory depression, the immediate antidote of choice is:

• Flumazenil
• Naloxone
• Activated charcoal only
• N-acetylcysteine

Correct Answer: Naloxone

Q15. Codeine’s analgesic potency relative to morphine is approximately:

• Identical potency to morphine
• About 1/6 to 1/10 as potent as morphine
• Twice as potent as morphine
• Non-analgesic in comparison

Correct Answer: About 1/6 to 1/10 as potent as morphine

Q16. Which clinical use is NOT an approved or common indication for codeine?

• Mild to moderate pain
• Cough suppression
• Treatment of opioid use disorder
• Adjunct to analgesics in combination products

Correct Answer: Treatment of opioid use disorder

Q17. Co-administration of codeine with strong CYP2D6 inhibitors may lead to:

• Increased conversion to morphine and toxicity
• Decreased analgesic effect due to reduced morphine formation
• Enhanced antitussive effect without analgesia change
• No clinically relevant interaction

Correct Answer: Decreased analgesic effect due to reduced morphine formation

Q18. Which genetic phenotype results in little or no conversion of codeine to morphine?

• Ultra-rapid metabolizer
• Extensive metabolizer
• Intermediate metabolizer
• Poor metabolizer

Correct Answer: Poor metabolizer

Q19. Codeine is contraindicated in children after tonsillectomy and/or adenoidectomy due to:

• Risk of bleeding
• Increased risk of opioid toxicity and respiratory depression
• Hypertensive crises
• Anticholinergic effects

Correct Answer: Increased risk of opioid toxicity and respiratory depression

Q20. The major route of elimination for codeine and its metabolites is:

• Fecal excretion
• Renal excretion in urine
• Exhalation via lungs
• Transdermal loss

Correct Answer: Renal excretion in urine

Q21. Which of the following best describes codeine’s bioavailability after oral administration?

• Nearly 100% due to no first-pass effect
• Low to moderate because of first-pass metabolism
• Zero because it is inactive orally
• Highly variable but always above 80%

Correct Answer: Low to moderate because of first-pass metabolism

Q22. A pharmacist counseling a patient on codeine should include which important advice?

• It has no potential for dependence
• Avoid driving or operating machinery until you know its effects
• Double the dose if pain is not relieved in 30 minutes
• Mix with alcohol to increase effectiveness

Correct Answer: Avoid driving or operating machinery until you know its effects

Q23. Which laboratory test might be useful to detect recent codeine use or its metabolites?

• Plasma glucose
• Urine drug screen for opioids, morphine
• Liver function tests only
• Complete blood count

Correct Answer: Urine drug screen for opioids, morphine

Q24. Codeine exerts its analgesic effect primarily by inhibiting which neuronal process?

• Serotonin reuptake
• Ascending nociceptive transmission in the dorsal horn
• Peripheral prostaglandin synthesis
• Voltage-gated sodium channels in peripheral nerves

Correct Answer: Ascending nociceptive transmission in the dorsal horn

Q25. Concomitant use of codeine with benzodiazepines increases the risk of:

• Seizures
• Enhanced respiratory depression and sedation
• Hypertensive emergency
• Excessive diuresis

Correct Answer: Enhanced respiratory depression and sedation

Q26. Which formulation of codeine provides an antitussive effect at lower doses than needed for analgesia?

• Injectable codeine phosphate
• Low-dose oral syrup preparations
• Transdermal patch
• Codeine suppositories

Correct Answer: Low-dose oral syrup preparations

Q27. Codeine’s therapeutic index is considered:

• Extremely wide, with no concerns for toxicity
• Narrower than non-opioid analgesics due to respiratory risk
• Wider than all other opioids
• Not applicable since it lacks toxicity

Correct Answer: Narrower than non-opioid analgesics due to respiratory risk

Q28. Which adverse effect of codeine typically requires prophylactic management in chronic use?

• Diarrhea
• Constipation
• Urinary incontinence
• Hair loss

Correct Answer: Constipation

Q29. In hepatic impairment, codeine dosing should be:

• Increased due to reduced clearance
• Unchanged in all cases
• Adjusted with caution or avoided depending on severity
• Switched to topical formulation only

Correct Answer: Adjusted with caution or avoided depending on severity

Q30. Which statement about codeine and pregnancy is most appropriate?

• Codeine is completely safe in all trimesters
• Use only if clearly needed and benefits outweigh risks; monitor neonate for withdrawal
• Contraindicated at conception only
• Encouraged for chronic pain management during pregnancy

Correct Answer: Use only if clearly needed and benefits outweigh risks; monitor neonate for withdrawal

Q31. Tolerance to which of the following effects of codeine develops most rapidly?

• Constipation
• Analgesic and sedative effects
• Pupillary constriction

Correct Answer: Analgesic and sedative effects

Q32. Codeine combined with paracetamol carries a risk of hepatotoxicity mainly from:

• Codeine-induced liver enzyme induction
• Excess paracetamol doses or accumulation over recommended limits
• Interaction producing N-nitroso compounds
• Renal failure leading to hepatic injury

Correct Answer: Excess paracetamol doses or accumulation over recommended limits

Q33. Which is a pharmacodynamic effect of codeine on the gastrointestinal tract?

• Increased gut motility
• Reduced gastric acid secretion only
• Decreased gastrointestinal motility leading to constipation
• Direct mucosal irritation causing ulcers

Correct Answer: Decreased gastrointestinal motility leading to constipation

Q34. A patient reports inadequate analgesia on codeine; which approach is appropriate for a pharmacist to recommend to the prescriber?

• Increase dose indefinitely until pain resolves
• Switch to a stronger opioid like morphine or consider adjuvant analgesics
• Stop all analgesics immediately
• Add an NSAID without assessing interactions

Correct Answer: Switch to a stronger opioid like morphine or consider adjuvant analgesics

Q35. Which of these is a common drug interaction that may increase codeine’s sedative effects?

• Rifampicin
• St. John’s wort
• Alcohol
• Metformin

Correct Answer: Alcohol

Q36. In therapeutic drug monitoring for opioids, why is it important to know if a patient is on codeine?

• Because codeine always shows as benzodiazepines on tests
• Because codeine is metabolized to morphine and may affect urine opioid panels interpretation
• Because codeine prevents all other drug metabolism
• Because codeine is not detectable in biological fluids

Correct Answer: Because codeine is metabolized to morphine and may affect urine opioid panels interpretation

Q37. Which symptom is most characteristic of acute opioid withdrawal after abrupt cessation of codeine?

• Bradycardia and hypothermia
• Flu-like symptoms with lacrimation and rhinorrhea
• Severe hyperglycemia
• Rapid hair growth

Correct Answer: Flu-like symptoms with lacrimation and rhinorrhea

Q38. The chemical class to which codeine belongs is:

• Benzodiazepines
• Phenylpiperidines
• Opium alkaloids (morphinan derivatives)
• Barbiturates

Correct Answer: Opium alkaloids (morphinan derivatives)

Q39. Which monitoring parameter is essential when initiating codeine in elderly patients?

• Bone density
• Renal function, respiratory status, and sedation level
• Ophthalmic pressure
• Thyroid function tests

Correct Answer: Renal function, respiratory status, and sedation level

Q40. Codeine’s efficacy as an analgesic compared to NSAIDs in inflammatory pain is generally:

• Superior in all cases
• Equal or sometimes less effective for inflammatory components; combination therapy may be needed
• Completely ineffective in inflammatory pain
• Always preferred over NSAIDs due to safety

Correct Answer: Equal or sometimes less effective for inflammatory components; combination therapy may be needed

Q41. Which regulatory measure has been implemented in many countries to reduce codeine-related harm?

• Unrestricted OTC sales
• Rescheduling to prescription-only or restricting pediatric use
• Mandating combination with benzodiazepines
• Removing all label warnings

Correct Answer: Rescheduling to prescription-only or restricting pediatric use

Q42. Which clinical test or assessment helps predict a patient’s response to codeine therapy?

• CYP2D6 genotyping
• Blood glucose measurement
• Chest X-ray
• ECG monitoring

Correct Answer: CYP2D6 genotyping

Q43. Which symptom is least likely to be caused by therapeutic doses of codeine?

• Miosis (pinpoint pupils)
• Pruritus
• Severe hypertension
• Nausea and vomiting

Correct Answer: Severe hypertension

Q44. Codeine phosphate as a salt is used in formulations because:

• It has lower solubility and is less bioavailable
• Salt forms enhance stability and aqueous solubility for dosing
• It prevents any metabolism in the liver
• It converts codeine into an antagonist

Correct Answer: Salt forms enhance stability and aqueous solubility for dosing

Q45. Which counseling point is important regarding storage and disposal of codeine-containing products?

• Store in the refrigerator at all times
• Keep out of reach of children and dispose of unused medication safely
• Dispose by flushing down the toilet for safety
• Share leftover tablets with family if they have pain

Correct Answer: Keep out of reach of children and dispose of unused medication safely

Q46. In patients with renal impairment, accumulation of which metabolite may contribute to prolonged effects?

• Codeine-6-glucuronide
• Thebaine
• Acetylcodeine
• Codeine-sulfate

Correct Answer: Codeine-6-glucuronide

Q47. Which symptom would suggest an allergic reaction to codeine rather than a typical opioid adverse effect?

• Constipation
• Urticaria and angioedema
• Miosis
• Dry mouth

Correct Answer: Urticaria and angioedema

Q48. The term ‘ceiling effect’ is sometimes applied to codeine because:

• Increasing dose always produces proportional analgesia
• Beyond a certain dose, additional analgesic benefit is minimal while side effects increase
• It has no side effects at any dose
• It reverses its effects at very high doses

Correct Answer: Beyond a certain dose, additional analgesic benefit is minimal while side effects increase

Q49. Which of the following is an appropriate alternative analgesic strategy for a patient with known CYP2D6 poor metabolizer status?

• Continue codeine at higher doses
• Use an opioid that does not require CYP2D6 activation, such as morphine or oxycodone
• Switch to codeine plus a CYP2D6 inhibitor
• Stop all analgesics and use only cold compresses

Correct Answer: Use an opioid that does not require CYP2D6 activation, such as morphine or oxycodone

Q50. For quality use of medicines, which practice is important when dispensing codeine-containing products?

• Providing no information to avoid alarming the patient
• Checking for contraindications, interactions, and providing clear counseling on dose, side effects, and safe use
• Recommending alcohol to improve absorption
• Advising unlimited refills without prescriber review

Correct Answer: Checking for contraindications, interactions, and providing clear counseling on dose, side effects, and safe use

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