Terazosin is an α1-selective alpha blocker used to treat the 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 considerable 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 precisely by the alpha1-adrenergic receptors. Terazosin also improves the symptoms of irritation of the lower urinary tract, caused by the contraction of the local smooth muscle.
However, terazosin also has a fairly frequent drawback, which is the lowering of blood pressure. Since most patients with benign prostatic hyperplasia are older, this is also one of the most common side effects. The lowering of arterial pressure by terazosin occurs because the latter also induces the relaxation of the smooth muscles surrounding the larger vessels of the circulatory system, causing a widening of these vessels and consequently reducing peripheral resistance. This side effect can be a problem in patients who already suffer from arterial hypotension, in which terazosin can cause dizziness and fainting. If a fainting of the patient occurs after the administration of terazosine, it is recommended to lay the patient down, so as to favor blood circulation, and if necessary to ask for medical assistance. The administration of terazosin causes a clinically significant reduction in blood pressure, even in normotensive individuals, which continues for the next 24 hours at the time of intake; the manifestation of symptoms depends on the individual response of the patient and his / her habitual arterial pressure; therefore orthostatic side effects may occur, especially at the beginning of treatment with terazosin, in 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 terazosine therapeutic doses is associated with a decrease, compared to the pre-treatment values, of 2-5% of the total plasma cholesterol concentration, and a decrease of about 3-6% in the concentration of LDL and VLDL fractions taken together.
Terazosin is rapidly absorbed in the gastrointestinal tract following oral administration and reaches maximum plasma concentration in less than an hour. Terazosin also shows a high affinity for plasma proteins, to which about 95% of the absorbed drug is bound. Most of the drug is metabolized by the liver, undergoing only the first part of the liver, then eliminated with urine for about 40% and with faeces for about 60%. The half-life of terazosin is about 12 hours from the time of intake. Clinical studies have shown that in patients of very advanced age (or in geriatric age) the clearence (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 smooth muscles surrounding arteries and arterioles leads to a decrease in blood pressure. In this regard, it is appropriate to remember that terazosin tends to have a slightly greater affinity for the alpha 1 adrenergic receptors of the urinary tract, which makes it a drug more indicated in the treatment of the symptoms of benign prostatic hyperplasia.
Terazosine 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 commercially as a generic drug under the name of Terazosin, or under other fancy names.
Posology and method of use
Different dosages are used for the different types of terazosin treatment, because it is essential that the terazosin dose 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 occurring, such as sudden fainting due to excessive lowering of blood pressure.
If terazosine is used for the treatment of arterial hypertension, it is recommended to proceed by increasing the daily dosage in a progressive manner, roughly doubling the doses of intake at weekly intervals, until the desired therapeutic response is reached. Generally, however, 2 mg / day of terazosin is sufficient to control blood pressure. In some cases it can be up to 10 mg / day and from several clinical studies it has been confirmed 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 should be reduced and, if it becomes necessary, the dose adjustment should be repeated again. The simultaneous administration of terazosine together with other antihypertensive drugs should be done with great caution, because there is a risk of an opposite therapeutic effect, that is the appearance of severe arterial hypotension.
Even when terazosin is used to treat the symptoms of benign prostatic hyperplasia, it is recommended to make a dose adjustment, roughly doubling the dosage at regular intervals, every week or every two weeks, until the desired therapeutic response is reached. . However the most used doses are those of 5 mg / day and 10 mg / day, while the improvement in the symptoms of benign prostatic hyperplasia begins to appear after about fifteen days from the start of terazosin administration. To avoid the appearance of orthostatic hypotension it is recommended to start therapy using 1 mg terazosin tablets, for a period of one week, then continue with the 2 mg tablets for the next two weeks and switch to 5 mg tablets of terazosin for one week. The improvement in the 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 hepatic function requires special attention, because terazosin is almost completely metabolised by the liver and excreted mostly from the bile duct; therefore, in the case of patients suffering from impaired liver function, it is recommended to make a very accurate adjustment of the therapeutic dose.
At the beginning of treatment with terazosine it is important that the first dose is administered to the patient before bedtime, to help the body become accustomed to lowering the pressure and to avoid the onset of vertigo and sudden syncope. The other doses of the treatment can also be administered in the morning, or at other times of the day, as long as there is a daily regularity, which will follow throughout the duration of the treatment.
The administration of terazosin should not be stopped without first consulting your doctor, especially if it is used to treat high blood pressure; if treatment is accidentally interrupted, 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 »
