Men's Health (incl Pharmacology) Flashcards
Describe the pathogenesis of BPH.
There are 2 components to BPH - the static component, where prostate tissue is enlarged due to hormonal action of DHT; dynamic component, where urethra outlet is narrowed due to agonism of a1 receptors and activation of smooth muscle tissue. These lead to urethral obstruction.
In the early phases, the bladder muscle is able to force urine through the narrowed urethra. Over time, this results in hypertrophy to overcome the obstruction. Once the detrusor muscle has achieved the highest rate of hypertrophy, it decompensates. The muscle becomes irritable and overly sensitive, contracting abnormally to small amounts of urine in bladder, resulting in various urinary symptoms.
Define Benign Prostatic Hyperplasia (BPH).
BPH is characterized by non-malignant growth of some components (e.g. transitional zone) of the prostate.
It is a progressive condition, with the presence of lower urinary tract symptoms (LUTS), and can negatively impact one’s quality of life.
What are the signs and symptoms of BPH?
(Early phase) Obstructive/voiding symptoms
- Dribbling
- Sensation of incomplete emptying
- Hesitancy
- Weak stream
- Straining
- Intermittent flow
(Late phase/left untreated) Irritative/storage symptoms
- Urinary incontinence
- Dysuria
- Nocturia
- Frequency
- Urgency
State various assessments of BPH.
1) Digital Rectal Exam (DRE): Normal prostate should be smooth; additional lumps might indicate BPH -> need for further evaluation
2) Ultrasonography
3) Maximum urinary flow rate
4) Prostate-specific antigen (PSA)
- Elevation may be a good indicator of BPH; positively correlated to prostate volume
- >1.5ng/mL indicate likely progression of BPH
5) Post-void residual (PVR)
- <100mL: normal
- >200mL: inadequate emptying
6) Medication history assessment
Describe the classification of the different severities of BPH, according to the American Urology Association Scoring Index (AUA - SI).
Mild: 7 or less. Asymptomatic or mildly symptomatic.
Moderate: 8-19. Both obstructive and irritative symptoms definitely present.
Severe: 20 or more. Symptomatic + 1 or more complications of BPH.
Describe the approach as to whether pharmacological treatment should be started in a patient diagnosed with BPH.
If patient
- Has mild BPH or
- Has moderate/severe BPH but unbothered by symptoms (does not affect QoL),
Do NOT start pharmacological treatment. Conduct watchful monitoring instead (more frequent monitoring of LUTS symptoms, labs etc).
Start clinical treatment if
- patient is bothered by symptoms, or
- if complications occur.
List the non-pharmacological strategies to manage BPH.
- Limit caffeine and alcohol intake
- Limit fluid intake at night
- Advise patients to take their time to completely empty their bladders on each occasion
- Consider removing medications that can exacerbate urinary symptoms, if there are no strong indications/has alternatives.
State the MoA of a1 receptor antagonists.
Reversibly inhibit a1 adrenergic receptors on smooth muscles of prostate, prostatic urethra, bladder neck and peripheral vasculature (non-selective).
This leads to decrease in muscle tone, relaxation of smooth muscle, relieving bladder obstruction.
What are the indications for a1 receptor antagonists?
General:
- For patients with moderate to severe symptomatic BPH, AND prostate size <40g
Do a1RAs reduce prostate size and/or delay BPH progression and need for surgery?
No. It only provides symptomatic relief.
Signs and symptoms of BPH are likely to recur if medication is discontinued.
Describe the onset of the vasodilatory effect of a1RAs.
Relatively fast (days to weeks)
Compare and contrast non-selective and uroselective a1RAs (including comparison for need to dose titrate)
Non-selective a1RAs antagonise both peripheral vascular and urinary a1 receptors.
- E.g. doxazosin, terazosin
- Need to titrate slowly to therapeutic dose, to minimise risks of hypotension and syncope
Uroselective a1RAs target urinary a1 receptors selectively hence lesser risks of hypotension.
- E.g. alfuzosin, tamsulosin, silodosin
- Dose titration not necessary
List the side effects of a1RAs.
- General: muscle weakness, fatigue, back pain
- Intra-operative floppy iris syndrome (IFIS)
- headache, dizziness, first-dose syncope, orthostatic hypotension (non-selective > selective; consider administering at bedtime to decrease these SE.)
- delayed/retrograde ejaculation (uroselective > non-selective; < sexual dysfn than 5ARIs)
How is tamsulosin metabolised?
In the liver, by CYP3A4 and CYP2D6 enzymes
What is the dose of tamsulosin? (FYI)
0.4mg orally once daily
How is tamsulosin eliminated?
Urine
State the MoA of 5-alpha reductase inhibitors (5ARIs).
Inhibit Type II 5-alpha reductase in prostate tissues. Decreases the conversion of testosterone to DHT, reducing prostate size.
State the compelling indications for use of 5ARIs. (4)
- Patients with moderate to severe LUTS with large prostate (>40g)
- Patients who want to avoid surgery
- Patients who are intolerant to side effects of a1RAs
- PSA >1.5ng/mL
Do 5ARIs slow progression of BPH and delay need for surgery?
Yes
Describe the onset of effect of 5ARIs.
Slow onset of action (may take up to 6-12 mths to decrease prostate size)
List the side effects of 5ARIs. (5 total)
- Ejaculatory disorders (reduced semen, delayed ejaculation)
- Decreased libido
- ED
- Gynecomastia, breast tenderness
- Hypotension (less compared to a1RAs)
State the indications for use of PDE-5Is in BPH.
- Add-on therapy, especially for patients with BPH + ED
- Increasing evidence of monotherapy for BPH, but still controversial
State the general indications for use of combination therapies in BPH.
Patients with moderate to severe symptoms (AUA - SI score of 8 and above) and prostate size >25g
Which PDE-5I is FDA-approved for use in BPH?
Tadalafil
Do PDE-5Is have an effect on prostate size?
No
List the specific indications and considerations (pros and cons) for each combination therapy for BPH.
1) a1RA + 5ARI
- Reserved for symptomatic pts with enlarged prostate
- Dilatory effect (fast onset) + dec in prostate size (slow onset)
- Disadvantage: Worsen or new onset ED
2) 5ARI + PDE-5I
- Mitigate sexual adverse effects that may arise from concomitant ED/5ARI
- Do not initiate PDE-5I if pt has unstable angina (due to nitrate use)
3) a1RA + PDE-5I
- Dual vasodilator therapy
- Rarely used due to possible severe life-threatening hypotension
- Keep doses of both drugs as low as possible
- Optimise a1RA dose first before adding PDE-5I
- Does not have an effect on prostate size
State the indications for use of anti-muscarinics in BPH.
Add-on for patients with irritative voiding symptoms, which mimic overactive bladder.
PVR must be <250mL (if not too much urine will be retained in bladder upon initiation)
State the dose of Finnasteride. (FYI)
5mg orally once daily
How is Finasteride metabolised?
CYP3A4
How is Finasteride eliminated?
50% excreted unchanged in faeces
Metabolites also found in urine and faeces
Define erectile dysfunction (ED).
Persistent (6 months or more) inability to achieve or maintain an erection of sufficient duration and firmness to complete satisfactory intercourse
What is the normal range of testosterone levels?
300-1000ng/dL (10-40nmol/L)