Benign Hypertrophy of Prostate (BHP)

BENIGN HYPERTROPHY OF PROSTATE (BHP)


 

BENIGN HYPERTROPHY OF PROSTATE (BHP)

  • Causes urinary obstruction.
  • Static component of obstruction – Occurs due to increased prostate size.
  • Dynamic component – Occurs due to increased tone of bladder neck/prostate smooth muscle.

Management:

I) Drugs used:

1. Selective α1-Blockers:

MOA:

  • α-adrenoceptor activation in bladder trigone, prostate & prostatic urethra, increases smooth muscle tone.
  • α-adrenoceptor blockade (particularly α-1 receptor) causes,  
    • Smooth muscle relaxation in neck of urinary bladder & prostatic urethra.
    • Reduces dynamic obstruction.
    • Increases urinary flow rate.
    • Cause complete bladder emptying in BHP patients.

Uses:

  • Relieves dynamic obstruction in BHP.
  • Provides rapid symptomatic relief in BHP.

Advantages:

  • Relieves voiding symptoms (hesitancy, narrowing of stream, dribbling & increased residual urine) effectively.
  • Also relieves irritative symptoms (urgency, frequency & nocturia).
  • Afford faster (within 2 weeks) & greater symptomatic relief (than finasteride).
  • Does not affect prostate size.

Disadvantage:

  • Effects last only till drug is given.
  • Benefit declines after few years of continued therapy, due to disease progression.
  • Taken concurrently with finasteride for long-term relief.

Drugs:

  • Prazosin, terazosin, silodosin, doxazosin & alfuzosin – DOC for benign hyperplasia of prostate (BHP).
  • Case-specific management:
    • DOC for BHP cases with hypertension – Prazosin/Doxazosin.
    • DOC for BHP cases without hypertension –Tamsulosin
  • Prazosin:
    • MOA – Blocks α1 receptors in bladder trigone & prostatic smooth muscle –> Improves urine flow & reduces residual urine in bladder.
  • Tamsulosin & Silodosin:
    • Selective inhibitor of α1A receptor (α1 subtype) present in prostate.
  • Advantage:
    • Doesn’t affect receptors in blood vessels – Hence, reduced propensity to cause postural hypotension.
    • Thus preferred for BHP treatment.

2. 5-α reductase inhibitors:

  • 5-α reductase – Enzyme converting DHT to testosterone.
  • Important drugs: 
    • Finasteride & dutasteride.
  • MOA:
    • Testosterone mediates important mechanisms like growth of prostate, male pattern baldness and hirsutism in females, via DHT.
    • By blocking 5-α reductase enzyme, conversion of dihydrotestosterone to testosterone is blocked –> reduced DHT production –> Prostate gland growth is influenced.
    • Hence, BHP treated by arresting growth/reducing prostate size.

Individual drugs:

  • Finasteride:
  • MOA:
    • Antagonist of 5α-reductase, mainly type II.
    • Inhibits conversion of testosterone to dihydrotestosterone & reduces prostate volume.
  • Uses:
    • Moderately effective in reducing prostate size in men with benign prostatic hyperplasia.
    • Used for relieving static component of urinary obstruction in BHP.
    • By reducing serum & prostatic concentrations of dihydrotestosterone –> prostatic volume decrease & urine flow rate increases
    • Delayed action; hence, takes >3 months to exert its beneficial effect.
  • Dose: 5 mg OD, review after 6 months.
  • Adverse effect:
    • Decreased libido
    • Erectile dysfunction
    • Ejaculation disorder – Decreased ejaculates volume.
    • Increased risk of hypospadias.
  • Disadvantage: 
    • Drug withdrawal causes re-growth of prostate.
    • On continued therapy, benefit is maintained for 3 years or more.  

Exam Important

BENIGN HYPERTROPHY OF PROSTATE (BHP)

  • Drugs used for treating BHP include Selective α1-blockers & 5-α reductase inhibitors.
  • α-adrenoceptor blockade results in smooth muscle relaxation in neck of urinary bladder & prostatic urethra, reduces dynamic obstruction, increases urinary flow rate & causes complete bladder emptying in BHP patients.
  • Selective α1-blockers relieves dynamic obstruction & provides rapid symptomatic relief in BHP.
  • Selective α1-blockers afford faster (within 2 weeks) & greater symptomatic relief (than finasteride).
  • Selective α1-blockers relieves voiding symptoms (hesitancy, narrowing of stream, dribbling & increased residual urine) effectively.
  • Selective α1-blockers does not affect prostate size.
  • Selective α1-blockers includes prazosin, terazosin, silodosin, doxazosin & alfuzosin. 
  • Selective α1-blockers are DOC for BHP.
  • DOC for BHP cases with hypertension is Prazosin/Doxazosin.
  • DOC for BHP cases without hypertension –Tamsulosin.
  • Prazosin blocks α1 receptors in bladder trigone & prostatic smooth muscle –> Improves urine flow & reduces residual urine in bladder.
  • Tamsulosin & Silodosin acts by selectively inhibiting α1A receptor (α1 subtype) present in prostate.
  • Tamsulosin & Silodosin has reduced propensity to cause postural hypotension, hence preferred for treating BHP.
  • 5-α reductase inhibitors like Finasteride & dutasteride.
  • 5-α reductase enzyme converts DHT to testosterone.
  • 5-α reductase inhibitors block 5-α reductase enzyme, conversion of dihydrotestosterone to testosterone is blocked –> reduced DHT production –> Prostate gland growth is controlled.
  • 5-α reductase inhibitors treats BHP by arresting growth/reducing prostate size.
  • 5-α reductase inhibitors are used for relieving static component of urinary obstruction in BHP.
  • Finasteride is 5α-reductase antagonistmainly type II.
  • Finasteride inhibits conversion of testosterone to dihydrotestosterone & reduces prostate volume.
  • Finasteride reduces serum & prostatic concentrations of dihydrotestosterone –> prostatic volume decrease & urine flow rate increases, hence useful for BHP treatment.
  • Finasteride exhibits delayed action; hence, takes >3 months to exert its beneficial effect.

 

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