36.8: Alpha Blockers and 5-Alpha-Reductase Inhibitors
By the end of this section, you should be able to:
- 36.8.1 Identify the characteristics of alpha blockers and 5-alpha-reductase inhibitor drugs used to treat benign prostatic hyperplasia (BPH).
- 36.8.2 Explain the indications, actions, adverse reactions, and interactions of alpha blockers and 5-alpha-reductase inhibitor drugs used to treat benign prostatic hyperplasia (BPH).
- 36.8.3 Describe nursing implications of alpha blockers and 5-alpha-reductase inhibitor drugs used to treat benign prostatic hyperplasia (BPH).
- 36.8.4 Explain the client education related to alpha blockers and 5-alpha-reductase inhibitor drugs used to treat benign prostatic hyperplasia (BPH).
Benign Prostatic Hyperplasia
Benign prostatic hyperplasia (BPH) is the nonmalignant enlargement of the prostate gland. This condition usually begins in mid-life and increases in prevalence as male individuals age. Studies have reported that about 8% of males in the fourth decade of life have BPH. That number increases significantly to about 50% in the sixth decade of life and 80% in the ninth decade of life (GBD 2019 Benign Prostatic Hyperplasia Collaborators, 2022; Ng & Barahdi, 2022). Two primary classes of medications used to treat BPH are alpha blockers and 5-alpha-reductase inhibitors .
BPH is also associated with complications such as urinary tract infection, acute urinary retention, urolithiasis, and acute renal failure as well as impacting other aspects of life, such as sleep quality, mood, social and sexual well-being, and safety related to increased falls (GBD 2019 Benign Prostatic Hyperplasia Collaborators, 2022).
Alpha Blockers
Alpha blockers are indicated to treat BPH. They work by relaxing the smooth muscle of the bladder neck and prostate to allow for an easier flow of urine. Alpha blockers include alfuzosin, doxazosin, tamsulosin, silodosin, and terazosin. Clients with smaller prostates often experience results more quickly.
Alpha blockers should be taken daily at the same meal, either breakfast or dinner (evening meal).
Table 36.26 lists common alpha blockers and typical routes and dosing for adult clients.
| Drug | Routes and Dosage Ranges |
|---|---|
|
Tamsulosin
( Flomax ) |
0.4 mg orally once daily. May be increased to 0.8 mg once daily after 2–4 weeks if needed. |
|
Doxazosin
( Cardura ) |
1 mg given once daily either in the morning or evening. May be increased at 1- to 2-week intervals to 2 mg, 4 mg, and 8 mg daily (maximum dose). |
|
Alfuzosin
( Uroxatral ) |
10 mg extended-release tablet orally once daily. |
|
Silodosin
( Rapaflo ) |
8 mg orally once daily. |
|
Terazosin
( Prostera ) |
1 mg orally once daily at bedtime. May increase to 2 mg, 5 mg, and 7.5 mg gradually once daily. |
Adverse Effects and Contraindications
Adverse effects might include dizziness and hypotension, especially when combined with other drugs that lower blood pressure. Retrograde ejaculation may occur, a harmless condition in which semen goes back into the bladder instead of out the tip of the penis. Other adverse effects include priapism, somnolence, dry mouth, dyspnea, fatigue, palpitations, headache, upper respiratory infections, abdominal pain, dyspepsia, constipation, nausea, and impotence.
Since clients with BPH could have coexisting erectile dysfunction, they may also take PDE5 inhibitors. Concomitant use of alpha blockers and PDE5 inhibitors can cause a severe drop in blood pressure. Additionally, signs and symptoms of prostate cancer and BPH are similar. Thus, ruling out cancer as the underlying issue is a priority before initiating alpha blockers.
Table 36.27 is a drug prototype table for alpha blockers featuring tamsulosin. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
|
Drug Class
Alpha blocker Mechanism of Action Relaxes the smooth muscle of the bladder neck and prostate |
Drug Dosage
0.4 mg orally once daily. May be increased to 0.8 mg once daily after 2–4 weeks if needed. |
|
Indications
Treatment of the signs and symptoms of benign prostatic hyperplasia Therapeutic Effects Allows easier flow of urine through the ureter |
Drug Interactions
Ketoconazole and similar drugs Erythromycin Cimetidine PDE5 inhibitors Food Interactions Grapefruit and grapefruit juice |
|
Adverse Effects
Dizziness, vertigo Retrograde ejaculation Postural hypotension Priapism |
Contraindications
Hypersensitivity |
5-Alpha-Reductase Inhibitors
The 5-alpha-reductase inhibitors such as finasteride and dutasteride block conversion of testosterone to dihydrotestosterone, resulting in shrinkage of the prostate gland. Improvement is not seen until the client has been on the medication for several weeks. Maximum results should occur about 6 months after the start of treatment. The prostate-specific antigen (PSA) can be decreased about 50%, and the prostate volume may be reduced by as much as 25% (Ng & Baradhi, 2022; Salisbury & Tadi, 2023).
Indications for 5-alpha-reductase inhibitors are BPH and male pattern baldness, but this section focuses only on BPH. Table 36.28 lists common 5-alpha-reductase inhibitors and typical routes and dosing for adult clients.
| Drug | Routes and Dosage Ranges |
|---|---|
|
Finasteride
( Proscar , Propecia ) |
5 mg orally once daily. |
|
Dutasteride
( Avodart ) |
0.5 mg orally once daily. |
Adverse Effects and Contraindications
Adverse effects related to 5-alpha-reductase inhibitors include erectile dysfunction, decreased ejaculatory volume, decreased libido, gynecomastia, orthostatic hypotension, dizziness, and weakness. Dutasteride may be combined with an alpha blocker to enhance the treatment of BPH. If so, the client has a greater chance of experiencing orthostatic hypotension, dizziness, and weakness.
Table 36.29 is a drug prototype table for 5-alpha-reductase inhibitors featuring finasteride. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
|
Drug Class
5 alpha-reductase inhibitor Mechanism of Action Shrinks the size of the prostate gland |
Drug Dosage
5 mg orally once daily. |
|
Indications
BPH Male pattern baldness Therapeutic Effects Improves urine flow in males |
Drug Interactions
Drugs that cause hypotension and dizziness may increase the risk of these side effects Food Interactions No significant interactions |
|
Adverse Effects
Hypotension Dizziness Increase in high-grade prostate cancer Breast changes including neoplasm Erectile dysfunction Libido, ejaculation, and orgasm disorders Male infertility |
Contraindications
Hypersensitivity Pregnancy |
Nursing Implications
The nurse should do the following for clients using alpha blockers or 5-alpha reductase inhibitors:
- Conduct history and physical to determine any underlying condition, such as prostate cancer, that should be treated first. Also determine other medical conditions that may be impacting urological health (diabetes, cardiovascular, obesity, etc.).
- Obtain medication history, noting any medications that may interact with alpha blockers or alpha reductase inhibitors (drugs that may cause hypotension or dizziness).
- Obtain necessary laboratory and diagnostic testing.
- Assess smoking and alcohol use.
- Assess balance and alertness because hypotension and dizziness are side effects of both alpha blockers and alpha reductase inhibitors. Somnolence is a side effect of alpha blockers.
- Provide emotional support and resources for client.
- Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.
Client Teaching Guidelines
The client taking an alpha blocker or a 5-alpha-reductase inhibitor should:
- Understand the medication’s purpose, side effects, contraindications, and precautions. Take alpha blocker medications ½ hour following the same meal each day (either breakfast or dinner/evening meal).
- Understand the risks to females, especially pregnant females, of handling crushed or broken tablets (5-alpha-reductase inhibitors).
- Monitor any signs and symptoms of adverse effects and report them to the health care provider.
- Know how to manage the side effects of specific 5-alpha-reductase inhibitor therapy, especially related to safety (risk of falls).
- Know how to manage the side effects of specific alpha blocker therapy (dizziness, priapism, hypotension).
- Verbalize the importance of follow-up appointments to manage the medication regimen and to observe for adverse effects.
- Understand drug, food, and/or herbal interactions that could be harmful.
- Use caution when driving, operating machinery, or performing other tasks requiring alertness when taking alpha blockers.
The client taking an alpha blocker or a 5-alpha-reductase inhibitor should not:
- Change position quickly when taking alpha blockers to minimize the risk of postural hypotension, especially when taking other medications that lower blood pressure.
- Not allow females of childbearing age to handle 5-alpha-reductase inhibitors, especially if the tablets are crushed or broken.