Erectile dysfunction is a common condition experienced by 18% of men over 20 in the US. It becomes more prevalent with age and when conditions are present.
Noncancerous enlargement of the prostate, known as benign prostatic hyperplasia (BPH), is common in aging men, can cause numerous lower urinary tract symptoms, and frequently occurs with erectile dysfunction.
In this article, we'll discuss the link between BPH and erectile dysfunction and how medications like doxazosin could be ideal for patients with erectile dysfunction.
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Doxazosin belongs to a group of medicines known as alpha-blockers, which lower blood pressure by blocking alpha-1 adrenergic receptors.
These receptors are also found on the prostatic smooth muscle, so blockage causes the smooth muscle of the bladder, neck, and prostatic urethra to relax. This prevents norepinephrine (a neurotransmitter and hormone, also known as noradrenaline) from tightening muscles in blood vessels, allowing them to remain open, which improves blood flow.
Doxazosin is available as an immediate-release tablet (under the brand name Cardura) that works immediately for a short time. It is also available as an extended-release tablet (under the brand name Cardura XL) with a delayed onset but longer-lasting effect.
Doxazosin, in either form, is usually taken once a day.
Doxazosin has two FDA-approved uses:
Treating hypertension (high blood pressure)
Improving urination and relieving lower urinary tract symptoms (LUTS) in men with noncancerous enlargement of the prostate (BPH)
When used to treat high blood pressure, doxazosin is often prescribed with other medications such as diuretics (water pills). When treating severe BPH, doxazosin may be used in combination with finasteride to prevent the progression of prostate enlargement.
Healthy, controlled blood flow is essential for stimulating and maintaining an erection. To fully understand how hypertension and BPH affect the penis, let's look at how erections occur and how poor blood flow can prevent them from lasting.
Flaccid penis: Inside the penis is a sponge-like tissue called the corpora cavernosa. This tissue consists of smooth muscle and blood vessels that do not hold large amounts of blood when the penis is not aroused.
Tumescent penis: When sexually aroused, the nervous system relaxes the muscles in the penis that control blood flow, thus widening the blood vessels inside the corpora cavernosa. Arousal allows more blood into the penis, causing it to swell.
Erect penis: As blood flows into the corpora cavernosa, the blood vessels become constricted, trapping the blood in the penis. The pressure of the trapped blood causes the penis to become firm and allows for sexual intercourse.
High blood pressure is associated with an increase in the release of vasoconstrictors (agents that constrict blood vessels) such as:
The continual release of these hormones and peptides can lead to dysfunction of the endothelial lining of the blood vessels in the corpus cavernosum and a diminished response to neurovascular stimulation.
Nitrous oxide is a common vasodilator (an agent that dilates blood vessels) and causes penile blood vessels to widen and let blood into the penis. There is intense nitrergic innervation (nitrous oxide stimulation) in the prostate, which is diminished in BPH, and the importance of nitrous oxide for the erectile function is well known.
Therefore, these two conditions go hand in hand.
Furthermore, both urinary function and erectile function are tied to adrenergic changes and associated with smooth muscle tonus. Patients with LUTS symptoms may have an altered adrenergic state that can affect erectile function.
While many medicines for high blood pressure can cause erectile dysfunction, alpha-blockers such as doxazosin do not typically cause this condition. Numerous studies¹ have shown that doxazosin has an alleviating effect on erectile dysfunction and lower urinary tract symptoms.
Doxazosin helps to relax smooth muscle and widen blood vessels. This reaction can help relieve symptoms of BPH by relaxing the prostate in the area around the bladder, reducing pressure, and making it easier to urinate. Doxazosin also blocks alpha-1 receptors responsible for vasoconstriction.
The combination of increased vasodilation and preventing constriction helps doxazosin reduce blood pressure. While this occurs in the entire body, it also affects penile tissue, and vasodilation will help improve blood flow into the penis.
Doxazosin is approved to treat high blood pressure and BPH, but both can contribute to erectile dysfunction. Doxazosin must be prescribed by a doctor. While it is not prescribed specifically for erectile dysfunction, it can help relieve erectile dysfunction in individuals suffering from high blood pressure and BPH.
Doxazosin should be taken to treat high blood pressure or BPH and is not intended to be used in the same way as Viagra or Cialis. In other words, this medication should not be taken to achieve an erection, even though it may help erections occur.
Taking the medication at bedtime is recommended to prevent side effects such as dizziness or fainting. The initial dose will start low and may be increased over time at your doctor's discretion.
Taking this medicine at the same time every day is essential. As with all medications, always read the patient information leaflet provided.
Doxazosin works by widening blood vessels. This effect is similar to the way that other oral medications for erectile dysfunction work, such as phosphodiesterase-5 (PDE5) inhibitors like sildenafil (Viagra) or tadalafil (Cialis).
If doxazosin is taken in combination with PDE5 inhibitors, it may lead to low blood pressure (hypotension) in some patients. A doctor should be consulted before using these medications together with doxazosin.
Reading the patient leaflet or any provided information is important, as the dosing of doxazosin differs depending on the condition being treated. For hypertension, the immediate-release form of doxazosin is typically recommended, while the extended-release form should only be taken to treat BPH.
A recent study² on BPH and sexual dysfunction noted that extended-release doxazosin also alleviated erectile dysfunction.
Hypertension: Immediate release doxazosin is recommended for treating hypertension, and the dose range varies from 1mg to 16mg per day. Treatment will start on a lower dose of 1 mg, increased to 2mg daily for one to two weeks. This dosage may be increased again if needed; however, the usual dose range is 2–4mg per day.
BPH: Extended-release tablets (Cardura XL) may be prescribed for BHP. Do not chew the pills; swallow them whole. The initial dose is 1mg per day and will be increased over time depending on the severity of symptoms. The maximum recommended dose is 8mg per day, but the usual dose is 2–4mg per day.
Doxazosin is generally safe for elderly patients, but it should be used with care as it may cause postural hypotension or a form of low blood pressure that causes faintness and dizziness when moving from lying down to sitting to standing.
For patients with BHP, doxazosin relieves lower urinary tract symptoms, reducing pain and making urination easier.
Doxazosin acts as a multitargeted therapy by improving bladder function and erectile dysfunction. It simultaneously relieves pain and sexual discomfort, improving confidence in the bathroom and bedroom.
Some users may experience prolonged and painful erections (priapism) of up to four hours or longer when using doxazosin. Contact a doctor if this occurs because prolonged and painful erections can permanently damage the penis.
The main risk of taking doxazosin is the potential for interactions with other medications used to treat erectile dysfunction, such as Viagra and Cialis. Anyone sensitive to quinazolines should be cautious when taking this medication for erectile dysfunction.
Hypertension and BPH can both cause erectile dysfunction. Typical medications used to treat hypertension can have a negative effect on penile health, which contributes to worsening erectile dysfunction. Doxazosin may be an alternative for other hypertensive treatments as it is not known to cause erectile dysfunction.
When taking doxazosin, it's important to be aware that it can have adverse effects if combined with oral medications for erectile dysfunction, such as Viagra and Cialis.