Drugs for erectile dysfunction – Sildenafil MCQs With Answer

Drugs for erectile dysfunction – Sildenafil MCQs With Answer

Sildenafil is a prototype PDE5 inhibitor widely taught in B.Pharm pharmacology. This introduction reviews mechanism of action, pharmacokinetics, clinical uses, adverse effects, drug interactions and dosage considerations relevant to Drugs for erectile dysfunction and Sildenafil. Key concepts include nitric oxide–cGMP pathway, selectivity for PDE5 versus PDE6, metabolism by CYP3A4/CYP2C9, onset and duration, contraindications with nitrates, and patient counselling points. Understanding these topics helps pharmacy students advise on safe use, recognize emergencies like priapism, and manage interactions with alpha-blockers, protease inhibitors or grapefruit juice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary mechanism of action of sildenafil in treating erectile dysfunction?

• Activation of guanylate cyclase
• Inhibition of phosphodiesterase type 5 (PDE5)
• Direct stimulation of nitric oxide (NO) release
• Blocking alpha-adrenergic receptors

Correct Answer: Inhibition of phosphodiesterase type 5 (PDE5)

Q2. Sildenafil increases penile erection by increasing the levels of which intracellular second messenger?

• cAMP
• cGMP
• IP3
• Diacylglycerol

Correct Answer: cGMP

Q3. Which enzyme isoforms primarily metabolize sildenafil?

• CYP1A2 and CYP2D6
• CYP3A4 and CYP2C9
• CYP2E1 and CYP2C19
• CYP4A11 and CYP2B6

Correct Answer: CYP3A4 and CYP2C9

Q4. What is the approximate oral bioavailability of sildenafil?

• ~10%
• ~40%
• ~80%
• ~100%

Correct Answer: ~40%

Q5. Typical time to maximum plasma concentration (Tmax) after oral sildenafil under fasting conditions is about:

• 5–6 hours
• 1 hour
• 15–30 minutes
• 12–24 hours

Correct Answer: 1 hour

Q6. Which of the following factors delays sildenafil absorption and reduces peak concentration?

• Taking with a high-fat meal
• Taking with water on an empty stomach
• Splitting the tablet into halves
• Chewing the tablet before swallowing

Correct Answer: Taking with a high-fat meal

Q7. The main ocular adverse effect of sildenafil is attributed to inhibition of which PDE isoform in the retina?

• PDE1
• PDE5
• PDE6
• PDE7

Correct Answer: PDE6

Q8. Which of the following is an absolute contraindication to sildenafil use?

• Concurrent nitrates therapy
• Mild controlled hypertension
• Diabetes mellitus
• Stable hyperlipidemia

Correct Answer: Concurrent nitrates therapy

Q9. Recommended initial adult dose of sildenafil for erectile dysfunction is usually:

• 5 mg
• 25 mg
• 50 mg
• 200 mg

Correct Answer: 50 mg

Q10. For elderly patients or those with hepatic impairment, which dosing adjustment is commonly recommended?

• Increase dose to 100 mg
• No change required
• Decrease starting dose to 25 mg
• Switch to intravenous sildenafil

Correct Answer: Decrease starting dose to 25 mg

Q11. The most serious urologic adverse effect that requires immediate attention is:

• Headache
• Priapism
• Flushing
• Dyspepsia

Correct Answer: Priapism

Q12. Which interaction increases sildenafil plasma levels significantly and may require dose reduction?

• Co-administration with rifampicin
• Co-administration with ketoconazole
• Co-administration with carbamazepine
• Co-administration with St. John’s wort

Correct Answer: Co-administration with ketoconazole

Q13. Sildenafil is available clinically as which salt form?

• Sildenafil hydrochloride
• Sildenafil citrate
• Sildenafil sulfate
• Sildenafil phosphate

Correct Answer: Sildenafil citrate

Q14. Compared to tadalafil, sildenafil has which characteristic?

• Longer half-life and longer duration of action
• Shorter half-life and shorter duration of action
• Higher selectivity for PDE11
• Administered once weekly

Correct Answer: Shorter half-life and shorter duration of action

Q15. Which counseling point is most important when dispensing sildenafil to a patient taking alpha-blockers?

• Alpha-blockers increase efficacy; no precautions needed
• Take sildenafil only with a large meal
• Start sildenafil at a low dose and monitor for symptomatic hypotension
• Stop alpha-blocker therapy before starting sildenafil

Correct Answer: Start sildenafil at a low dose and monitor for symptomatic hypotension

Q16. Which adverse effect is commonly reported and related to vasodilation from sildenafil?

• Constipation
• Flushing
• Proteinuria
• Hirsutism

Correct Answer: Flushing

Q17. Which statement about sildenafil pharmacokinetics is true?

• It is primarily excreted unchanged in urine
• It undergoes extensive hepatic metabolism before renal excretion of metabolites
• It is not metabolized and has no active metabolites
• It is absorbed only via sublingual route

Correct Answer: It undergoes extensive hepatic metabolism before renal excretion of metabolites

Q18. Which laboratory parameter is most relevant to monitor when assessing risk of sildenafil accumulation in severe organ impairment?

• Serum creatinine and liver function tests
• Complete blood count
• Fasting blood glucose
• Serum calcium

Correct Answer: Serum creatinine and liver function tests

Q19. Which condition may reduce the clinical effectiveness of sildenafil?

• Uncontrolled diabetes with vascular disease
• Mild seasonal allergies
• Well-controlled hypothyroidism
• Recent influenza immunization

Correct Answer: Uncontrolled diabetes with vascular disease

Q20. Sildenafil’s visual disturbance (blue tint) is due to cross-reactivity with which receptor/pathway?

• Muscarinic receptors in the eye
• Inhibition of retinal PDE6 affecting phototransduction
• Direct antagonism of cone opsins
• Elevation of intraocular pressure

Correct Answer: Inhibition of retinal PDE6 affecting phototransduction

Q21. For pulmonary arterial hypertension (PAH), sildenafil dosing differs. Which is true?

• Sildenafil is never used for PAH
• Sildenafil is used at lower doses and different frequency as Revatio®
• PAH dosing uses a single 200 mg weekly dose
• PAH dosing is identical to erectile dysfunction dosing

Correct Answer: Sildenafil is used at lower doses and different frequency as Revatio®

Q22. Which herbal or food interaction can increase sildenafil levels via CYP3A4 inhibition?

• Grapefruit juice
• St. John’s wort
• Green tea
• High-fiber cereals

Correct Answer: Grapefruit juice

Q23. Maximum recommended frequency for sildenafil dosing for erectile dysfunction is:

• Once every 4 hours
• Once daily (no more than once per day)
• Three times daily
• Every 6 hours as needed

Correct Answer: Once daily (no more than once per day)

Q24. Which population requires dose reduction or caution due to reduced clearance of sildenafil?

• Young healthy adults
• Patients with severe hepatic impairment
• Patients with treated hypothyroidism
• Patients using topical antibiotics

Correct Answer: Patients with severe hepatic impairment

Q25. Which of the following best describes sildenafil’s chemical classification?

• An alpha-adrenergic agonist
• A phosphodiesterase type 5 inhibitor
• A nitric oxide donor
• A calcium channel blocker

Correct Answer: A phosphodiesterase type 5 inhibitor

Q26. Which clinical sign should prompt immediate medical evaluation after sildenafil use?

• Transient mild headache
• Persistent erection lasting more than 4 hours
• Temporary mild nasal congestion
• Brief episode of flushing

Correct Answer: Persistent erection lasting more than 4 hours

Q27. Which statement is correct regarding sildenafil and nitrates interaction?

• Sildenafil potentiates nitrate-induced hypotension and they should not be co-administered
• Sildenafil antagonizes nitrates and reduces their effect
• They may be safely taken together with food
• Nitrates eliminate sildenafil side effects

Correct Answer: Sildenafil potentiates nitrate-induced hypotension and they should not be co-administered

Q28. A pharmacist advising a patient should recommend which timing for taking sildenafil relative to sexual activity?

• Take immediately after sexual activity
• Take 30–60 minutes before anticipated activity
• Take only in the morning before breakfast
• Take at bedtime only

Correct Answer: Take 30–60 minutes before anticipated activity

Q29. Which of the following drugs would likely decrease sildenafil plasma concentrations by inducing CYP3A4?

• Erythromycin
• Ritonavir
• Rifampicin
• Ketoconazole

Correct Answer: Rifampicin

Q30. From a pharmaceutical formulation standpoint, which attribute is important for oral sildenafil tablets?

• Enteric coating to avoid gastric absorption
• Film-coated immediate-release formulation for predictable onset
• Depot intramuscular formulation is standard
• Buccal patch delivery is the only approved form

Correct Answer: Film-coated immediate-release formulation for predictable onset

G S Sachin

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