Urology Drugs

Question 1

What is the primary cause of urethral obstruction in Benign Prostatic Hyperplasia (BPH)?

Answer 1

The primary cause is the enlargement of the prostate, which can obstruct the urethra, increasing resistance to urinary flow and making it difficult for the bladder to empty completely. The secondary cause is the

Question 2

Which enzyme is responsible for converting testosterone to dihydrotestosterone (DHT), and how does this affect BPH?

Answer 2

The enzyme 5-alpha-reductase converts testosterone into dihydrotestosterone (DHT). The overproduction of DHT in the prostate stimulates prostate growth, contributing to urethral obstruction in BPH

Question 3

What is the mechanism of action of 5-alpha reductase inhibitors in the treatment of BPH?

Answer 3

5-alpha reductase inhibitors block the conversion of testosterone to dihydrotestosterone (DHT), which reduces the size of the prostate and improves urinary flow over time

Question 4

Name common symptoms associated with urethral obstruction in BPH.

Answer 4

Postvoid Dribbling
Urgency
Overflow Incontinence

Question 5

Explain the difference between selective and non-selective alpha blockers used for treating BPH

Answer 5

Selective alpha blockers (e.g., Tamsulosin) specifically block alpha-1A receptors in the prostate, relaxing smooth muscles in the prostate and bladder neck without significantly affecting blood pressure.

Non-selective alpha blockers (e.g., Doxazosin) block both alpha-1A and alpha-1B receptors, reducing peripheral vascular resistance and lowering blood pressure in addition to improving urine flow.

Question 6

What are the advantages of combination therapy over single-drug therapy in the treatment of BPH?

Answer 6

Combination therapy, which includes both alpha blockers and 5-alpha reductase inhibitors, offers enhanced symptom relief by providing rapid symptom improvement from the alpha blocker and long-term prostate size reduction from the 5-alpha reductase inhibitor. It is particularly beneficial for patients with severe symptoms and large prostates.

Question 7

What is a major contraindication when prescribing PDE-5 inhibitors for erectile dysfunction (ED)?

Answer 7

PDE-5 inhibitors are contraindicated in patients taking nitrates (e.g., nitroglycerin) due to the risk of severe hypotension.

Question 8

Describe the mechanism of action of PDE-5 inhibitors in treating erectile dysfunction.

Answer 8

PDE-5 inhibitors block the enzyme phosphodiesterase type 5 (PDE-5), which increases the levels of cyclic guanosine monophosphate (cGMP) in the corpus cavernosum, promoting smooth muscle relaxation and increased blood flow to the penis, facilitating an erection.

Question 9

Which PDE-5 inhibitor has the longest half-life, and what is the significance of this?

Answer 9

Tadalafil (Cialis) has the longest half-life, allowing for more spontaneous sexual activity as its effects last up to 36 hours.

Question 10

What is the primary symptom of stress incontinence, and how does it differ from urge incontinence?

Answer 10

The primary symptom of stress incontinence is involuntary urine leakage during activities that increase intra-abdominal pressure, such as coughing or sneezing. This differs from urge incontinence, where the primary symptom is a sudden, intense urge to urinate followed by involuntary leakage.

Question 11

What role does the 5-alpha-reductase enzyme play in the development of BPH, and how do 5-alpha-reductase inhibitors address this?

Answer 11

The 5-alpha-reductase enzyme converts testosterone into dihydrotestosterone (DHT), a potent androgen that stimulates prostate growth. In BPH, the overproduction of DHT leads to prostate enlargement, contributing to urethral obstruction. 5-alpha-reductase inhibitors, such as finasteride and dutasteride, block this conversion, reducing DHT levels, which causes the prostate to shrink and improves urinary symptoms over time.

Question 12

Describe the difference between detrusor overactivity and detrusor underactivity in patients with BPH. How do these conditions affect urinary symptoms?

Answer 12

Detrusor Overactivity: This occurs when the bladder muscle contracts involuntarily due to increased resistance from an enlarged prostate. It leads to symptoms such as urgency, urge incontinence, and frequent urination, including nocturia.

Detrusor Underactivity: Prolonged urethral obstruction can weaken the bladder muscle, leading to incomplete bladder emptying and overflow incontinence. The bladder fills up, but due to weak contractions, it fails to empty completely, resulting in dribbling and retention.

Question 13

What are the main factors to consider when selecting an alpha blocker for a patient with BPH, particularly in terms of selectivity and side effects?

Answer 13

Selectivity: Selective alpha blockers (e.g., Tamsulosin) target alpha-1A receptors in the prostate and bladder neck, relaxing these muscles without significantly affecting blood pressure, making them ideal for patients who are sensitive to hypotension.
Non-selective alpha blockers (e.g., Doxazosin) block both alpha-1A and alpha-1B receptors, which not only relaxes the prostate but also reduces blood pressure, making them suitable for patients with hypertension.

Side Effects: Selective alpha blockers generally have fewer cardiovascular side effects compared to non-selective ones, which can cause orthostatic hypotension, dizziness, and fatigue.

Question 14

Why might a patient with BPH experience nocturia, and which pathophysiologic mechanism is responsible for this symptom?

Answer 14

Nocturia in BPH is often caused by detrusor overactivity, where the bladder muscle contracts involuntarily as it struggles against the increased urethral resistance caused by the enlarged prostate. This overactivity results in frequent urination, especially at night, as the bladder attempts to empty despite the obstruction.

Question 15

What specific conditions might require dose adjustments or caution when prescribing Silodosin for BPH?

Answer 15

Silodosin (Rapaflo) requires dose adjustments in patients with renal impairment, specifically those with severe chronic kidney disease (CKD). It may also be contraindicated in these patients due to its metabolism and excretion via the kidneys, necessitating careful monitoring and possible dose reduction

Question 16

Compare the onset of action and long-term benefits between alpha blockers and 5-alpha-reductase inhibitors in treating BPH.

Answer 16

Alpha Blockers: These medications, such as Tamsulosin, provide rapid symptom relief, typically within 7-10 days. They primarily improve urinary flow and reduce symptoms like urgency and frequency by relaxing the smooth muscles in the prostate and bladder neck.

5-Alpha Reductase Inhibitors: These drugs, such as Finasteride, have a slower onset of action, taking 9-12 months to reach maximum therapeutic effect. However, they offer long-term benefits by reducing the size of the prostate, leading to sustained symptom relief and a decreased need for surgical intervention.

Question 17

Why is Alfuzosin contraindicated in patients taking medications that prolong the QT interval, and what is the clinical significance of this interaction?

Answer 17

Alfuzosin can prolong the QT interval, which is a measure of electrical activity in the heart. When combined with other QT-prolonging drugs (e.g., certain antibiotics like Levofloxacin or antidepressants), it increases the risk of life-threatening arrhythmias such as Torsades de Pointes. This interaction is clinically significant in patients with pre-existing cardiovascular conditions or those taking other QT-prolonging medications, as it can lead to serious cardiac events.

Question 18

What are the primary adverse effects associated with 5-alpha reductase inhibitors, and why should these drugs be handled with caution by pregnant women?

Answer 18

The primary adverse effects of 5-alpha reductase inhibitors include sexual dysfunction (decreased libido, erectile dysfunction, and reduced ejaculate volume) and gynecomastia (enlargement of male breast tissue). These drugs are teratogenic and can cause birth defects in male fetuses. Pregnant women or women who may become pregnant should avoid handling broken or crushed tablets to prevent dermal absorption of the drug.

Question 19

What is the clinical significance of monitoring PSA levels in patients taking 5-alpha reductase inhibitors, and how do these medications affect PSA test results?

Answer 19

5-alpha reductase inhibitors reduce PSA levels by approximately 50%, so PSA test results must be interpreted with caution. If a patient is on one of these medications, their baseline PSA should be recorded, and any subsequent increase in PSA levels could indicate the presence of prostate cancer. Regular monitoring of PSA is important for ongoing assessment of prostate health.

Question 20

In patients with both BPH and hypertension, why might non-selective alpha blockers be preferred over selective alpha blockers?

Answer 20

Non-selective alpha blockers, such as Doxazosin or Terazosin, block both alpha-1A and alpha-1B receptors, leading to relaxation of the prostate and a reduction in peripheral vascular resistance. This dual effect makes them suitable for patients who also require blood pressure management, as they can simultaneously treat BPH and hypertension.

Question 21

What medications are given for BPH under 5 alpha reductase inhibitors?

Answer 21

1. Terazosin (Hytrin)
2. Doxazosin (Carduro)
3. alfuzosin (Uroxatral)

Question 22

What medications are given for BPH under alpha blockers?

Answer 22

1. Finasteride
2. Dutasteride

Question 23

Describe the role of nitric oxide (NO) in the physiology of a penile erection.

Answer 23

Nitric oxide (NO) is released from nerve endings in the penis during sexual stimulation. It activates the enzyme guanylate cyclase, which increases cyclic guanosine monophosphate (cGMP) levels in smooth muscle cells. This causes a decrease in intracellular calcium levels, leading to the relaxation of smooth muscle in the cavernosal arteries, allowing increased blood flow into the corpora cavernosa. This blood flow causes the erectile tissue to expand, leading to an erection.

Question 24

Which PDE-5 inhibitor has the fastest onset of action, and what clinical advantage does this offer?

Answer 24

Avanafil (Stendra) has the fastest onset of action, typically within 30-45 minutes. The clinical advantage is that it allows for quicker spontaneous sexual activity compared to other PDE-5 inhibitors, which may take longer to become effective.

Question 25

Compare and contrast the half-lives of Sildenafil and Tadalafil, and explain how this affects their clinical use.

Answer 25

Sildenafil has a shorter half-life of about 4-5 hours, which requires more planning around sexual activity, as its effects last for a shorter duration.

Tadalafil, on the other hand, has a much longer half-life of 17.5 hours, allowing for more spontaneity, as its effects can last up to 36 hours. This longer duration makes Tadalafil more suitable for patients who prefer not to plan sexual activity around medication timing.

Question 26

Why is Tadalafil also indicated for the treatment of benign prostatic hyperplasia (BPH), and what is the mechanism behind this dual indication?

Answer 26

Tadalafil is indicated for the treatment of both erectile dysfunction and benign prostatic hyperplasia (BPH) because it relaxes the smooth muscles in the bladder and prostate through its inhibition of PDE-5. This dual mechanism improves urinary flow in BPH patients while also facilitating erections by increasing blood flow to the penis

Question 27

What are the clinical considerations for the use of PDE-5 inhibitors in patients with cardiovascular disease, and what alternative treatments might be considered?

Answer 27

PDE-5 inhibitors should be used with caution in patients with cardiovascular disease, especially those taking nitrates or who have unstable angina, as the combination can cause life-threatening hypotension. In such patients, alternative treatments such as Alprostadil (via injection or intraurethral suppository) or non-pharmacologic options like penile implants may be considered to avoid systemic cardiovascular effects.