by egpat 16 May 2024
What are the similarities and differences between these two drugs, tamsulosin and finasteride? Tamsulosin is available under the brand name Flomax; it is available as its salt tamsulosin hydrochloride; on the other hand, finasteride is available under the brand name Proscar. Both of these drugs, tamsulosin hydrochloride and finasteride, can be used in one of the conditions of benign prostatic hyperplasia, commonly known as BPH. This condition is observed in men with an age greater than 50 years. With the progression of age, prostate enlargement can be observed, resulting in benign prostatic hyperplasia that leads to the development of lower urinary tract symptoms.
So in such patients, we can observe increased frequency to urinate and increase urinary agency, but at the same time, urinary flow is going to be reduced, resulting in a weak stream of urine. So these symptoms can be reduced by both tamsulosin and finasteride, but the dosage is somewhat different. Flomax is available as a capsule in two different strengths, such as 0.4 mg and 0.8 mg. But proscar is available as a tablet at a strength of 5mg.
Even though both of these drugs are indicated for the treatment of BPH, there are few similarities and differences between these two drugs. In a few situations, tamsulosin is beneficial, but in other conditions, finasteride works better.
So here, let’s explore the various similarities and differences between tamsulosin and finasteride and in which conditions these drugs are preferred.
Tamsulosin is one of the alpha-1A blockers; this drug acts on the bladder, where alpha-1A receptors are expressed at different locations. On the bladder neck, they are expressed, as well as on the urethral smooth muscle attached to the prostate. When these alpha 1A receptors are activated, they produce the contraction of the smooth muscle, particularly at the bladder neck, resulting in increased pressure and an increased frequency of urination in the patients.
Similarly, these alpha 1A receptors are responsible for constriction of the urethral pathway, resulting in decreased urinary flow. Tamsulosin is an alpha-1A blocker; it can block these receptors, resulting in the relaxation of smooth muscle, which reduces the urinary frequency as well as increasing the urinary flow. That's why tamsulosin is well known by its brand name, Flomax, because it increases urinary flow. Now finasteride acts in a different way; finasteride is a 5-alpha reductase inhibitor. This drug is also indicated for BPH, which is associated with prostate enlargement.
Now, because of increased prostate size, it can produce some pressure on the bladder so that urinary urgency increases, but at the same time, because of increased prostate size, the urethral flow is also blocked, resulting in decreased urinary flow in such patients. So this results in urinary retention, and sometimes it requires surgery in order to restore the urinary flow. In those patients, finasteride can be given to reduce urinary retention as well as to prolong the time required for the surgical procedure, so finasteride can act on the prostate gland, thereby reducing the prostate size, which increases the urinary flow.
Both tamsulosin and finasteride can increase urinary flow, but they work in different ways. Tamsulosin produces relaxation of the bladder smooth muscle, whereas finasteride reduces prostate size. Even though both of these drugs are going to increase the urinary flow, tamsulosin has a greater effect on increasing the urinary flow compared with finasteride. That's why tamsulosin is used as the first-line drug in the initial stage of BPH because this drug can increase the urinary flow significantly, thereby reducing the lower urinary tract symptoms associated with BPH.
Normally, the prostate size can be measured by one of the factors of total prostate volume, commonly known as TPV. In normal, healthy people, the TPV will be less than 25 cc, but in men with BPH, the total prostate volume may be increased, which is associated with a few of the symptoms, such as increased urinary frequency and urgency along with decreased urinary volume.
In such conditions, tamsulosin can be used to relieve the symptoms where it increases the urinary flow, but with the progression of age as well as the progression of BPH, the total prostate volume may be increased so that it is greater than 30 cc. So when the TPV value is greater than 30 cc, it indicates prostate enlargement, but sometimes this total prostate volume may be greater than 40 cc. In such conditions, the monotherapy of tamsulosin is somewhat ineffective.
So when the TPV is greater than 30 to 40 cubic centimeters, tamsulosin should be combined with other drugs that reduce the prostate size. For instance, tamsulosin can be combined with dutasteride, which is again another beta-reductase inhibitor. But in patients with prostate enlargement, finasteride can be given because it reduces the prostate size, and it can be given as a monotherapy in order to reduce urinary retention.
Already, we have seen that tamsulosin can be used for the treatment of BPH. It is given at an initial dose of 0.4 mg. On the other hand, finasteride can be used in two conditions, and it is available under two brand names: Proscar and Propecia. Under the brand name Proscar, finasteride can be used for the treatment of BPH, where it is available as a 5 mg tablet, whereas under the brand name Propecia, finasteride can be used for the treatment of male pattern hair loss, and it is available at a dose of 1 mg.
A low dose of finasteride can be used for the management of male-pattern hair loss. This is another difference between tamsulosin and finasteride. Finasteride has two clinical uses: it can be used for both BPH and the treatment of hair loss, where it is given at a low dose.
We have seen that tamsulosin can be used to relieve the symptoms of BPH, and it is one of the first-line drugs in the initial treatment of BPH. This drug is given 30 minutes after first meal of each day, in order to reduce any adverse effects it is always given along with the meal particularly it is given at the first meal of the day just after 30 minutes, as when this drug is given along with food it can reduce any adverse effects associated with this drug.
But when this drug is given under fasting conditions, the absorption of tamsulosin is significantly increased, which increases the toxic effects, resulting in significant dizziness and hypotension in the patients. That's why this drug should not be given under fasting conditions; it should be given 30 minutes after the first meal of each day.
On the other hand, finasteride can be given either with food or without food because food does not have any significant effect on the bioavailability of finasteride. So this is another important difference between tamsulosin and finasteride: the intake of tamsulosin should be regular, and it is associated with the first meal of each day.
Both of these drugs, tamsulosin and finasteride, are indicated only in men for the treatment of BPH; they are not indicated in women or pregnant women; they are contraindicated. But the handling of finasteride is somewhat important because when this tablet is broken and comes into contact with the pregnant woman, there may be a chance of accidental consumption where the drug is absorbed into the fetus, resulting in some toxic effects on the male fetus.
That's why finasteride should be safely handled by the pregnant woman in order to prevent any toxic effects on the male fetus, as it produces some abnormal development of male genitalia, so finasteride should be carefully handled by pregnant women. That precaution is not observed with tamsulosin.
In patients with any history of orthostatic hypotension, we can observe a change in the blood pressure. With a change in posture, particularly when standing, the blood pressure is going to be reduced, resulting in either fainting or falling. In such patients, tamsulosin can increase dizziness as well as confusion because tamsulosin can increase the symptoms of orthostatic hypotension.
So for patients with any history of orthostatic hypotension, tamsulosin is contraindicated due to the enhanced effects of dizziness and confusion in the patients. But finasteride is not showing any significant orthostatic hypotension that was observed with tamsulosin, so this drug can be given to such patients with any orthostatic hypotension.
Testosterone is going to be converted into dihydrotestosterone by one of the five alpha-reductase enzymes. Now finasteride is going to inhibit the activity of this enzyme, thereby inhibiting the synthesis of dihydrotestosterone. When this activation is inhibited, finasteride can produce a few of the hormonal effects and may produce some impotence in the patients, as well as a loss of libido. Sexual desire can be reduced, and it can even produce erectile dysfunction, leading to ejaculation failure.
All these side effects are observed with finasteride because of its hormonal effects. On the other hand, tamsulosin can also show some effect on ejaculation. This drug can produce one of the conditions of priapism, which is a condition of prolonged erection of the penis for more than 4 hours, resulting in painful erection. Tamsulosin can also produce ejaculation failure because of prolonged erection, so both of these drugs may produce some ejaculatory problems. But being a hormonal agent, finasteride has a greater effect on these ejaculatory problems that may lead to impotence, loss of libido, and even increased breast tenderness and breast enlargement in men.
Tamsulosin is metabolized by the cytochrome p450 system. This drug can be converted into metabolites by the CYP3A4 enzyme, which is mainly responsible for the metabolism of tamsulosin; similarly, this drug can also be converted into metabolites by another enzyme, CYP2D6. Now any drug acting on these enzymes can produce drug interactions with tamsulosin. For instance, ketoconazole is a strong inhibitor of the CYP3A4 enzyme, thereby inhibiting the metabolism of tamsulosin. This results in increased levels of tamsulosin within the body, which leads to significant lightheadedness, dizziness, confusion, and orthostatic hypotension, which are more troublesome.
Similarly, drugs like paroxetine can inhibit CYP2D6 activity, thereby increasing the toxicity of tamsulosin. On the other hand, finasteride is free of these side effects; it has no significant interactions at the metabolic phase, so it can be safely given with other drugs that affect the cytochrome p450 system.
Both tamsulosin and finasteride can reduce PSA levels and prostate-specific antigen levels. Normally, in patients with prostate cancer, the PSA levels are increased, but with the use of either tamsulosin or finasteride, the PSA levels are reduced, which can mask the development of prostate cancer in the patient. That's why, before the use of these two drugs, a screening test should be done to check for any pre-existing prostate cancer in the patients.
The long-term use of tamsulosin can induce prostate cancer, as can finasteride, but the risk of prostate cancer is more pronounced with finasteride because of its anti-androgenic effects.
Tamsulosin is an alpha-1A blocker, so it can act as a smooth muscle relaxant, so it can produce relaxation of various smooth muscles where alpha-1A receptors are located. One of the locations is the eye, where tamsulosin can produce relaxation of the iris dilator muscle. This may result in poor pupillary dilatation and flaccid paralysis. That's why tamsulosin should be carefully given in cataract surgery because this drug can develop one of the syndromes, intra-operative floppy Iris syndrome (IFIS).
So during the cataract surgery, care should be taken with the use of tamsulosin, and special techniques should be utilized in order to prevent any development of intraoperative floppy Iris syndrome. Sometimes tamsulosin can also increase the post-operative intraocular pressure in patients, so this can be minimized with the proper use of cholinergic agents and antihistamines to control the intraocular pressure. On the other hand, finasteride is not showing any effect on cataracts, so it can be given during the cataract surgery.
So these are the various similarities and differences between tamsulosin and finasteride. In a few of the situations, tamsulosin shows some advantage; it can significantly increase the urinary flow, thereby relieving lower urinary tract symptoms associated with BPH. That's why tamsulosin is a first-line drug in the treatment of BPH, but this drug does not affect the prostate size and it will not reduce the prostate volume, so in those patients with significant prostate enlargement where the total prostate volume is greater than 30 cm or greater than 40 cm, finasteride works better because it reduces prostate size as well as prostate volume.
Tamsulosin is contraindicated in patients with orthostatic hypotension, and it also shows drug interactions that affect the metabolism of tamsulosin. On the other hand, finasteride can cause impotence in patients as well as erectile dysfunction; it should be used with caution in pregnant women due to teratogenic effects on male fetuses; and these are the various similarities and differences between tamsulosin and finasteride. Tamsulosin should be used to relieve the symptoms in patients associated with BPH, and finasteride should be used in those patients with excessive prostate enlargement. So that's all about the similarities and differences between tamsulosin and finasteride.