Terazosin is an α1-selective alpha blocker used to treat symptoms of benign prostatic hyperplasia.
The relaxation of the smooth muscles of the prostate and urethra is associated with an increase in the maximum speed of urinary flow and a significant reduction in obstruction, thus greatly improving the conditions of those suffering from benign prostatic hyperplasia (BPH). In fact, the symptoms of BPH are mainly caused by the presence of an enlarged prostate and by the increase in the tone of the smooth muscle of the bladder and prostate, which, as we have seen, is regulated by alpha1-adrenergic receptors. Terazosin also improves symptoms of lower urinary tract irritation caused by local smooth muscle contraction.
However, terazosin also has a fairly frequent drawback, which is the lowering of blood pressure.Since most patients with benign prostatic hyperplasia have an advanced age, this problem is also one of the most common side effects. The lowering of blood pressure by terazosin occurs because the latter also induces relaxation of smooth muscles surrounding the larger vessels of the circulatory system, causing these vessels to widen and consequently reduce peripheral resistance. This side effect can be a problem in patients who already suffer from arterial hypotension, in whom terazosin can cause dizziness and fainting . Should the patient become faint after the administration of terazosin, it is recommended to lay the patient down, in order to promote blood circulation, and if necessary to seek medical assistance. The administration of terazosin causes a reduction in blood pressure. clinically significant, even negl normotensive individuals, which continues for 24 hours following the time of recruitment; the manifestation of symptoms depends on the individual response of the patient and his / her habitual arterial pressure; therefore the orthostatic side effects can occur, especially at the beginning of treatment with terazosin, in very many individuals.
Another curious effect that occurs following the administration of terazosin is the lowering of the blood concentration of cholesterol. In fact, clinical studies have shown that the administration of therapeutic doses of terazosin is associated with a decrease, compared to the pre-treatment values, of the 2-5% of the total plasma cholesterol concentration, and an approximately 3-6% decrease in the concentration of the LDL and VLDL fractions taken together.
Terazosin is rapidly absorbed from the gastrointestinal tract following oral administration and reaches maximum plasma concentration in less than one "hour. Terazosin also exhibits a" high affinity for plasma proteins, to which approximately 95% of the absorbed drug binds. . Most of the drug is metabolized by the liver, undergoing only a minor part of the first hepatic passage, then eliminated in the urine for about 40% and in the faeces for about 60%. The half-life of terazosin is approximately 12 hours from the time of intake. Clinical studies have shown that in patients of very advanced age (or geriatric age) the clearance (the speed of elimination of the drug from the body) decreases by about 30% compared to the norm.
Terazosin is also used in the treatment of arterial hypertension, for which the pharmacological mechanism of action is always the same. In fact, the relaxation of the smooth muscle surrounding arteries and arterioles leads to a decrease in blood pressure. In this regard, it should however be remembered that terazosin tends to have a slightly higher affinity for the alpha 1 adrenergic receptors of the urinary tract, which makes it a more suitable drug in the treatment of symptoms of benign prostatic hyperplasia.
Terazosin was first introduced on the market by the pharmaceutical company Abott, in the United States, in 1987, under the registered name of Hytrin ®; nowadays terazosin can be found on the market as a generic drug under the name of Terazosin, or under other invented names.
Dosage and method of use
Different dosages are used for the different types of treatment with terazosin, because it is essential that the dose of terazosin is adjusted according to the individual response of each patient. In fact, at the beginning of each treatment, both of the symptoms of benign prostatic hyperplasia and of arterial hypertension, it is recommended to start with a dose of terazosin of only 1 mg / day, which should be administered before going to bed. this greatly reduces the chances of side effects, such as sudden fainting resulting from the excessive lowering of blood pressure.
If terazosin is used for the treatment of arterial hypertension, it is recommended to proceed by increasing the daily dosage progressively, approximately doubling the intake doses at weekly intervals, until the desired therapeutic response is achieved. Generally, however, 2 mg / day of terazosin is sufficient to control blood pressure, in some cases it can be as high as 10 mg / day and it has been confirmed by several clinical studies that this dose can be used for long periods of time as a maintenance dose. In some cases, in the treatment of arterial hypertension, terazosin is used in combination with other antihypertensive drugs, such as diuretic drugs; in these cases the dose of terazosin must be reduced and, if necessary, the dose adjustment must be repeated again. The simultaneous administration of terazosin together with other antihypertensive drugs should be done with great caution, because there is a risk of a therapeutic effect opposite, that is, the appearance of severe arterial hypotension.
Even when terazosin is used to treat symptoms of benign prostatic hyperplasia, it is recommended to adjust the dose by roughly doubling the dosage at regular intervals, every week or every two weeks, until the desired therapeutic response is achieved. However, the most used doses are those of 5 mg / day and 10 mg / day, while the improvement of symptoms of benign prostatic hyperplasia begins to appear after about fifteen days from the beginning of the administration of terazosin. To avoid the onset of terazosin. "Orthostatic hypotension it is recommended to start therapy using the 1 mg terazosin tablets, for a duration of one week, then continue with the 2 mg tablets for the next two weeks and switch to the 5 mg terazosin tablets for the duration one week. Improvement of symptoms of benign prostatic hyperplasia and response to treatment should be reviewed every month.
The use of terazosin in patients with moderately or severely impaired liver function requires special attention, because terazosin is metabolized almost entirely by the liver and excreted mostly by the bile duct; therefore in the case of patients suffering from impaired liver function very careful adjustment of the therapeutic dose is recommended.
At the beginning of treatment with terazosin it is important that the first dose is given to the patient before bedtime, to help the body get used to the lowering of blood pressure and to avoid the onset of dizziness and sudden syncope. The other doses of treatment may also be administered in the morning, or at other times of the day, as long as there is a daily regularity, which will follow for the entire duration of the treatment.
The administration of terazosin should not be stopped without first consulting your doctor, especially if it is used for the treatment of arterial hypertension; if treatment is interrupted by mistake, it is recommended to restart the administration of terazosin at a dose of 1 mg, to be taken before going to bed.
Terazosin: contraindications and side effects "
