Alpha Receptors and the Function of the Bladder and Prostate
The urinary bladder is dynamic: Its functions are to store and void urine. In coordination with the urinary bladder, the internal sexual organs -- prostate, seminal vesicles, vas deferens -- are also dynamic: They produce, store, and ejaculate semen. The prostate is intimately physically associated with the bladder and urethra, through which urine is voided.
The functions of the bladder and prostate are controlled by hormonal and neurological factors. Among the factors controlling the interplay of the bladder and prostate is a neurological pathway referred to as the adrenergic nervous system. This system is regulated partly by epinephrine, a hormone made in the adrenal gland and is also known as adrenaline, and by what is called the sympathetic nervous system. When the adrenergic system is active, it can cause such effects as high blood pressure and reduced intestine motility. Its activation can also contract the bladder neck and slow urination.
The actions of the adrenergic system are partly mediated by proteins knows as receptors. These are distributed to varying extents in the organs of the bodies and they fall into two broad categories: Alpha-receptors and Beta-receptors. For our purpose, the more interesting category is the alpha-receptors because they are distributed in the bladder neck and prostate. When they are active, they cause contraction that can interfere with urination. For this reason, men with weak urinary streams have been treated with alpha-blockers such as:
These medications can be very effective in providing relief from urinary urgency, frequency, and weak stream. As you can see, new kinds of alpha-blockers are introduced from time to time. While they are in the same general class of medication, chemical variations are introduced to affect specificity (bladder vs. arteries) and reduce side effects.
Alpha-Blockers in Prostatitis Treatment
Prostatitis is characterized by many possible types of complaints, among which urinary symptoms, perineal pain, and ejaculatory pain are common. Accordingly, given the experience with symptom relief with alpha-blockers for patients with urinary symptoms, it makes intuitive sense to direct alpha-blockers to the task of relieving some of the symptoms of prostatitis. Indeed, many patients are given alpha-blockers as a first-line therapy for their prostatitis. There are additional, less direct reasons to consider alpha-blockers in the treatment of prostatitis, including the facts that alpha-receptors in the central nervous system have apparently involved in some pain conditions and that they may be involved in reducing neurologically mediated inflammation. So how well have alpha-blockers performed in the treatment of prostatitis?
This subect has received considerable attention and there are enough data to permit several good reviews of the subject. For extensive details and a comprehensive reference list, the reader is referred to this excellent review: No Benefit of Alpha-blockers for Chronic Prostatitis.
Overall, here are some things to keep in mind when considering alpha-blockers as a treatment choice:
- Alpha-blockers may cause unwanted side effects, including low blood pressure and dizziness
- When properly selected, dosed and administered, alpha-blockers are generally well tolerated
- Alpha-blockers are designed to principally target the urinary component of prostatitis symptoms
- In well-conducted large trials of patients with chronic prostatitis, alpha-blockers have been generally unimpressive
- Trials have relied principally on tamsulosin (Flomax) and alfuzosin (Uroxatral); perhaps other medications will fare differently
- Alpha-blockers may work better in sub-classes of chronic prostatitis, e.g. those with subvesical obstruction
Click here to read about finasteride in the treatment of chronic prostatitis.
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