# Benign Prostatic Hyperplasia: Medical Therapy

## Introduction

Benign prostatic hyperplasia (BPH) is a histologic diagnosis defined by the non-malignant proliferation of stromal and epithelial cells within the transition zone of the prostate. It represents the most common benign neoplasm in men, with histologic prevalence reaching 50% by age 50 and 90% by age 80. BPH causes lower urinary tract symptoms (LUTS) through two main mechanisms: static obstruction, which results from the enlarged glandular tissue compressing the urethra, and dynamic obstruction, which arises from increased smooth muscle tone in the prostatic stroma and bladder neck. Medical therapy is considered the first-line treatment for moderate-to-severe LUTS attributed to BPH.

## Pathophysiology

### Static Component

The static component of BPH involves glandular hyperplasia in the periurethral transition zone, which compresses the prostatic urethra and contributes to obstruction. This process is driven primarily by dihydrotestosterone (DHT), a potent androgen converted from testosterone by the enzyme 5-alpha reductase type 2 within the prostate. Stromal-epithelial interactions and various growth factors, including fibroblast growth factor (FGF), epidermal growth factor (EGF), and insulin-like growth factor (IGF), promote nodular growth within the prostate. Additionally, estrogen may play a permissive role by upregulating androgen receptors in the prostatic stroma, facilitating this proliferative process.

### Dynamic Component

The dynamic component of obstruction is mediated by alpha-1 adrenergic receptors, predominantly the alpha-1A subtype, located in the smooth muscle of the prostate, bladder neck, and prostatic capsule. Increased sympathetic nervous system activity elevates smooth muscle tone in these areas, worsening urethral obstruction. This dynamic component accounts for approximately 40% of the urethral resistance seen in BPH.

### Secondary Bladder Changes

Chronic bladder outlet obstruction (BOO) due to BPH leads to compensatory detrusor hypertrophy, which may eventually progress to detrusor decompensation. Detrusor overactivity develops in 50-75% of men with BOO, contributing to storage LUTS such as urgency and frequency. With prolonged obstruction, progressive detrusor underactivity can occur, resulting in poor bladder emptying and elevated post-void residual (PVR) volumes.

## Clinical Evaluation

### Symptom Assessment

Symptom severity is commonly assessed using the International Prostate Symptom Score (IPSS), also known as the American Urological Association (AUA) Symptom Index. This tool consists of seven questions scored from 0 to 35, with mild symptoms defined as 0-7, moderate as 8-19, and severe as 20-35. A separate quality of life (bother) score, ranging from 0 to 6, gauges the patient’s distress and helps guide treatment decisions. A voiding diary can also be useful to document urinary frequency, nocturia, and volume per void.

### Physical Examination

A digital rectal examination (DRE) is performed to assess prostate size, nodularity, symmetry, and tenderness. However, DRE tends to underestimate the true prostate volume, and prostate size does not correlate well with symptom severity.

### Laboratory and Imaging

Urinalysis is essential to rule out infection or hematuria. Prostate-specific antigen (PSA) testing helps estimate prostate volume, as a PSA level greater than 1.5 ng/mL predicts a prostate volume exceeding 30 grams and assists in counseling about progression risk. Although serum creatinine is not routinely recommended by AUA guidelines, it should be considered if renal impairment is suspected. Measurement of post-void residual (PVR) urine volume is important, with elevated PVR values above 200-300 mL suggesting significant urinary retention. Transrectal or transabdominal ultrasound can be used to measure prostate volume, which guides therapy selection.

<image>Cross-sectional anatomic diagram of the prostate showing the transition zone with BPH nodular enlargement compressing the prostatic urethra, the peripheral zone, surgical capsule, alpha-1 adrenergic receptor distribution in the stroma and bladder neck, and the dynamic versus static components of obstruction</image>

## Medical Therapy Options

### Alpha-1 Adrenergic Blockers

Alpha-1 adrenergic blockers act by relaxing smooth muscle in the prostate stroma, capsule, and bladder neck through blockade of alpha-1A receptors, thereby reducing the dynamic component of obstruction. Symptom improvement typically occurs within days to two weeks. These agents reduce the IPSS by 4-6 points and improve peak urinary flow rate (Qmax) by 2-3 mL/s. Commonly used alpha-blockers include tamsulosin (0.4 mg daily), which is alpha-1A selective and the most frequently prescribed due to its lower risk of orthostatic hypotension; silodosin (8 mg daily), which is highly alpha-1A selective but associated with the highest incidence of retrograde ejaculation (28%); alfuzosin (10 mg extended-release daily), which is uroselective with a favorable cardiovascular profile; and doxazosin (1-8 mg daily) and terazosin (1-10 mg daily), both non-selective agents that require dose titration and have more cardiovascular side effects. Side effects of alpha-blockers include orthostatic hypotension (especially with non-selective agents), dizziness, retrograde ejaculation, and rhinitis. Tamsulosin is most strongly associated with intraoperative floppy iris syndrome (IFIS), a complication during cataract surgery; patients should inform their ophthalmologist before surgery, although discontinuation of the drug does not reliably prevent IFIS.

| Drug | Dose | Selectivity | Key Advantage | Notable Side Effect |
|---|---|---|---|---|
| Tamsulosin | 0.4 mg daily | Alpha-1A selective | Low orthostatic hypotension | IFIS (cataract surgery) |
| Silodosin | 8 mg daily | Highly alpha-1A selective | Effective; rapid onset | Retrograde ejaculation (28%) |
| Alfuzosin | 10 mg ER daily | Uroselective | Favorable CV profile | Dizziness |
| Doxazosin | 1-8 mg daily | Non-selective | Low cost | Orthostatic hypotension; requires titration |
| Terazosin | 1-10 mg daily | Non-selective | Low cost | Orthostatic hypotension; requires titration |

### 5-Alpha Reductase Inhibitors (5-ARIs)

5-Alpha reductase inhibitors block the conversion of testosterone to DHT, leading to a reduction in prostate volume by 20-30% over 6 to 12 months. Their onset of action is slow, with symptom improvement typically seen after 3-6 months and maximal effect reached at 6-12 months. These agents reduce the IPSS by 3-5 points and are most effective in men with prostates larger than 30-40 grams. Finasteride (5 mg daily) inhibits type 2 5-alpha reductase, while dutasteride (0.5 mg daily) inhibits both type 1 and type 2 isoenzymes, resulting in greater DHT suppression (>90% versus 70%). Unique benefits of 5-ARIs include a 57% reduction in the risk of acute urinary retention and a 34% reduction in the need for surgery, as demonstrated in the MTOPS and CombAT trials. Side effects include decreased libido (3-5%), erectile dysfunction (5-8%), decreased ejaculate volume, and gynecomastia (1-2%). Because 5-ARIs reduce PSA levels by approximately 50% at six months, the PSA value must be doubled when screening for prostate cancer. Any confirmed rise in PSA while on a 5-ARI should prompt further evaluation. Post-finasteride syndrome, characterized by persistent sexual and neuropsychiatric symptoms after discontinuation, is controversial but acknowledged by the FDA.

### Combination Therapy (Alpha-Blocker + 5-ARI)

Combination therapy with an alpha-blocker and a 5-ARI has been shown to be superior to either monotherapy in reducing clinical progression of BPH. The MTOPS trial demonstrated that doxazosin plus finasteride reduced progression risk by 66%, while the CombAT trial showed that dutasteride plus tamsulosin was more effective than monotherapy, particularly in men with prostate volumes greater than 30 grams and PSA levels above 1.5 ng/mL. Combination therapy is recommended for men with moderate-to-severe LUTS and enlarged prostates who are at risk of progression, although it is associated with a higher incidence of side effects compared to monotherapy.

### Phosphodiesterase-5 Inhibitors (PDE5-Is)

Tadalafil 5 mg daily is the only PDE5 inhibitor FDA-approved for the treatment of BPH/LUTS. It works by increasing cyclic guanosine monophosphate (cGMP) in prostatic smooth muscle, bladder, and urethra, reducing smooth muscle tone and possibly modulating afferent nerve signaling. Tadalafil reduces the IPSS by 4-5 points but does not significantly improve Qmax. It is particularly suitable for men with both LUTS and erectile dysfunction. However, tadalafil cannot be combined with nitrates or alpha-blockers without appropriate precautions due to the risk of hypotension.

### Anticholinergics and Beta-3 Agonists (for Storage LUTS)

For men with predominant storage symptoms such as urgency and frequency, anticholinergic agents like tolterodine and solifenacin may be added to alpha-blockers. Beta-3 agonists such as mirabegron or vibegron offer a safer alternative in men with bladder outlet obstruction, as they carry a lower risk of urinary retention compared to anticholinergics. Careful monitoring of PVR is essential, and anticholinergics should be avoided in patients with PVR greater than 250-300 mL or severe bladder outlet obstruction.

<image>Flowchart for medical management of BPH showing initial evaluation with IPSS and prostate volume, mild symptoms managed with watchful waiting, moderate-to-severe symptoms stratified by prostate size for alpha-blocker monotherapy versus combination therapy, with add-on options including PDE5 inhibitors and anticholinergics for storage LUTS</image>

## Watchful Waiting and Lifestyle Modifications

Watchful waiting is appropriate for men with mild symptoms (IPSS less than 8) and low bother scores. Behavioral modifications can help alleviate symptoms and include fluid restriction in the evening, avoidance of caffeine and alcohol, double voiding, timed voiding, and limiting diuretic use before bedtime. Reviewing medications is important to discontinue or substitute drugs that may worsen LUTS, such as anticholinergics, decongestants, opioids, and calcium channel blockers. Patients should undergo annual reassessment with IPSS, PVR measurement, and uroflowmetry.

## Indications for Surgical Referral

Surgical referral is indicated for patients with refractory urinary retention after a catheter trial, recurrent urinary tract infections attributable to BPH, recurrent gross hematuria from prostatic bleeding, bladder stones secondary to obstruction, renal insufficiency due to obstructive uropathy, or failure of or intolerance to medical therapy with persistent moderate-to-severe LUTS.

<image>Bar graph comparing efficacy of BPH medical therapies showing IPSS reduction and Qmax improvement for alpha-blockers, 5-ARIs, combination therapy, and tadalafil, with overlaid data from MTOPS and CombAT trials</image>

## Key Clinical Pearls

Alpha-blockers provide rapid symptom relief within days to weeks and are considered first-line therapy for LUTS regardless of prostate size. In contrast, 5-alpha reductase inhibitors are most beneficial in men with prostates larger than 30 grams, as they reduce the risk of acute urinary retention and the need for surgery, although their effects take 3 to 6 months to manifest. Combination therapy with an alpha-blocker and a 5-ARI offers superior efficacy compared to monotherapy in men at risk of progression, such as those with large prostates, elevated PSA, and moderate-to-severe symptoms. It is essential to double the PSA value in patients taking 5-ARIs to accurately interpret cancer screening results. Tadalafil 5 mg daily is an excellent option for men who have both LUTS and erectile dysfunction. Patients on alpha-blockers should be warned about the risk of intraoperative floppy iris syndrome before cataract surgery, a risk that persists even after discontinuation of the medication.

## References

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2. Roehrborn CG, Siami P, Barkin J, et al. The effects of combination therapy with dutasteride and tamsulosin on clinical outcomes in men with symptomatic benign prostatic hyperplasia: 4-year results from the CombAT study. *Eur Urol*. 2010;57(1):123-131.  
3. Foster HE, Barry MJ, Dahm P, et al. Surgical management of lower urinary tract symptoms attributed to benign prostatic hyperplasia: AUA guideline. *J Urol*. 2018;200(3):612-619.  
4. Oelke M, Bachmann A, Descazeaud A, et al. EAU guidelines on the treatment and follow-up of non-neurogenic male lower urinary tract symptoms including benign prostatic obstruction. *Eur Urol*. 2013;64(1):118-140.