Prototype Drug Unit 3 & 4- Sildenafil (Viagra)

Question 1

Therapeutic classification

Answer 1

Drug for treating impotence

Question 2

Pharmacologic classification

Answer 2

Phosphodiesterase-5 inhibitor

Question 3

Therapeutic effects and uses

Answer 3

First drug approved for Erectile Dysfunction. Also used for pulmonary arterial HTN.

Question 4

Mechanism of action

Answer 4

Relaxes smooth muscle in the corpus cavernosa, allowing increased blood flow into the penis and allowing a harder and longer alsting erection in about 70% of men.

Question 5

Route

Answer 5

PO

Question 6

Absorption

Answer 6

Rapid; bioavailability 40%

Question 7

Distribution

Answer 7

96% protein bound

Question 8

Metabolism

Answer 8

Hepatic

Question 9

Excretion

Answer 9

80% feces; 12% renal

Question 10

Adverse effects

Answer 10

headache, dizziness, flushing, rash, and nasal congestion

Hypotension occurs when taking organic nitrates for angina and can result in MI and sudden cardiac death

Question 11

Contraindications/Precautions

Answer 11

Contraindications: patients taking organic nitrates, hypersensitivity, severe cardiovascular disease, recent MI, stroke, heart failure, or dysrhythmias, and in the presence of anatomic deformities of the penis. Preexisting visual disturbances

Precautions: renal or hepatic impairment

Question 12

Drug interactions

Answer 12

Cimetidine, erythomycin, and ketoconazole will increase serum levels. Nitrates is contraindicated and will cause hypotension and even death. Protease inhibitors will cause increased sildenafil levels which leads to toxicity. Rifampin decreases its levels.

Question 13

Herbal/food interactions

Answer 13

High-fat meals should be avoided because absorption will be decreased. Grapefruit juice increases the plasma concentrations of sildenafil and may cause adverse effects

Question 14

Pregnancy category

Answer 14

B (Not approved for women)

Question 15

Nursing responsibilities

Answer 15

1) Complete history and physical examination
2) Complete drug history
3) Baseline vital signs
4) Notify prescriber if patient takes drugs for angina or HTN such as nitroglycerin
5) Monitor liver function tests
6) Monitor for visual adverse effects
7) Monitor for presence of headache, dizziness, flushing, rash, and nasal congestion

Question 16

Patient Family Education

Answer 16

1) Keep all lab visits to evaluate liver function
2) 30-60 min before anticipated sexual activity. No more than one dose in 24 hours
3) Alert all health care providers to the use of sildenafil
4) Avoid high-fat meals before taking this drug
5) Immediately report any chest pain, unrelieved visual changes, eye pain, lights or flashes in ht eyes, or an erection that lasts longer than 4 hours or is painful