What Are Thiazides?

Thiazine diuretics are also known as moderateefficacydiuretics or Na + -CL- cotransporter inhibitors. They mainly act on the proximal end of the distal tubule, and represent a drug: hydrochlorothiazide.

Thiazine diuretics are a type of antihypertensive drug, which can be used alone to treat early hypertension or in combination with other antihypertensive drugs for moderate to severe hypertension.

Drug Name: Thiazide diuretics
Main indications: Early hypertension

Adverse reactions: Long-term use can reduce glucose tolerance and increase blood sugar
Athletes use with caution: Use with caution
Attributes: Antihypertensive drug

Definition of thiazide diuretics

Thiazine diuretics are a class of oral diuretics and antihypertensive drugs widely used clinically. The drug consists of a heterocyclic benzothiadiazine and a sulfonamide group. The drugs of this class have similar effects. They can achieve the same effect only in different dosages. Hydrochlorothiazide is the prototype drug of this class of drugs. Commonly used thiazines include chlorothiazide, indapamide, and chlorthalidone. ^[1]

Mechanism of thiazide diuretics

The thiazide diuretics act on the distal end of the ascending branch of the myelin and the proximal end of the distal curved tubule, inhibiting the reabsorption of Na and Cl, and play a role in diuretic and diuretic. Due to the increase of Na flowing into the distal curved tubule and collecting tube, sodium Potassium exchange increases, so excretion of K is increased, and its diuretic effect is moderate. Diuretic effect, increased excretion of urinary sodium, potassium, chlorine, phosphorus, and magnesium, while decreased excretion of urinary calcium. The action mechanism of this class of drugs mainly inhibits the reabsorption of sodium chloride in the anterior segment of the distal tubule and the proximal tubule (lighter), thereby increasing the Na + -K + exchange in the distal tubule and the collecting duct and increasing K + secretion. Its mechanism of action is not fully understood. This class of drugs can inhibit carbonic anhydrase activity to varying degrees, so it can explain its effect on proximal tubules. This class of drugs can also inhibit phosphodiesterase activity, reduce fatty acid uptake and mitochondrial oxygen consumption in the renal tubules, thereby inhibiting the active reabsorption of Na + and Cl- by the renal tubules. ; Induces vasodilators, such as bradykinin, prostaglandin (PGI2), etc., in the vessel wall. Therefore, in addition to blood pressure reduction of thiazide diuretics, an important blood pressure reduction mechanism is to reduce peripheral vascular resistance, especially its long-term blood pressure lowering effect. ^[1] ^[2]

Common drugs for thiazide diuretics

Thiazines include chlorothiazide, hydrochlorothiazide (dihydrogram urine plugs), cyclopentazine, benzylfluorothiazide, and chlorothiazide. These drugs can inhibit the reabsorption of NaKCl and water from the ascending branch cortex of the renal tubule and the anterior segment of the distal tubule. Low toxicity, overdose or prolonged use can cause dose-dependent pharmacological adverse reactions. Adverse reactions include: 1, ion disorders, hyperuricemia 3, hyperglycemia and so on.

Adverse reactions of thiazide diuretics

There are some adverse reactions when taking thiazide diuretics, as follows:

Hyponatremia, hypochloremia, and hypokalemia alkalemia: Hypokalemia is the most common adverse reaction, and intermittent therapy or combined with potassium-sparing diuretics can be used for prevention, or supplemented in time. Potassium salt.

Hyperglycemia: long-term use can cause decreased glucose tolerance and elevated blood sugar, which can be recovered after stopping the drug. Diabetes patients can increase blood sugar, but it is not serious. Therefore, this type of medicine is not absolutely forbidden for patients with diabetes.

Hyperuricemia: Thiazines can interfere with the excretion of uric acid from the renal tubules, increasing the level of uric acid in the blood, which can aggravate the condition of gout patients.

Azotemia: As thiazide drugs reduce the glomerular filtration rate, reduce blood volume, and aggravate azotemia, severe renal impairment may induce renal failure.

Increase blood ammonia: This class of drugs has a weak inhibitory effect on carbonic anhydrase, and long-term application will cause blood ammonia to increase. For those who have severely impaired liver function, there is a danger of inducing abnormal liver function.

Hyperlipidemia: It can increase blood cholesterol, triacylglycerol and low density lipoprotein, and reduce high density lipoprotein.

Allergic reactions: such as photosensitive dermatitis, thrombocytopenia, and necrotizing vasculitis.

Pharmacokinetics of thiazide diuretics

There are two types of thiazide diuretics commonly used clinically: thiazide-type and thiazine-like diuretics. The former includes hydrochlorothiazide, benzfluorothiazine, and the like; the latter includes indapamide, chlorothionone, and the like. Pharmacokinetics: The bioavailability of hydrochlorothiazide is 60% to 70%, the duration is 16 to 24 hours, 95% is excreted by the kidney, and the elimination half-life is 9 to 10 hours; the bioavailability of benzfluthiazine is 90%, and the duration 12 ~ 18h, 30% excreted by the kidney, cleared half-life 9h; chlorothionone bioavailability is 65%, duration 48 ~ 72h, 65% excreted by the kidney, cleared half-life 50-60h; bioavailability of indapamide The degree is 93%, the duration is 24 hours, and the half-life of elimination is 18 hours after metabolism by the liver. ^[1]

Pharmacological effects of thiazide diuretics

1. Diuretic effect: Thiazines can enhance the excretion of NaCl and water, and produce a mild and long-lasting diuretic effect, but long-term use can lead to hypokalemia. The effects of thiazide drugs depend on the production of prostaglandins, and their effects can also be Inhibited by non-steroidal anti-inflammatory drugs.

2 , anti-diuretic effect: thiazide diuretics can significantly reduce urine output and thirst symptoms in patients with diabetes insipidus, mainly due to reducing the osmotic pressure of blood plasma to reduce thirst. Its anti-diuretic mechanism is unclear and needs further study

3. Antihypertensive effect: Thiazine diuretics are commonly used antihypertensive drugs. In the early stage of medication, blood pressure is reduced by diuretic and blood volume reduction, and in the long-term medication, the blood pressure is reduced by expanding peripheral blood vessels. ^[3]

Clinical application of thiazide diuretics

1 Edema: can be used for edema caused by various reasons. It has good curative effect on mild and moderate cardiogenic edema and is one of the main therapeutic drugs for chronic cardiac insufficiency. The curative effect on renal edema is related to the degree of renal function damage. The less severe damage is better. Hepatic edema should prevent hypokalemia-induced hepatic coma when using this class of drugs.

2 Hypertension: This class of drugs is one of the basic drugs for the treatment of hypertension. It is often used in combination with other antihypertensive drugs to reduce the dose of the latter and reduce side effects. ^[3]

3 Others: It can be used for nephrogenic diabetes insipidus and pituitary diabetes insipidus in which vasopressin is ineffective. It can also be used for those with high urinary calcium and kidney stones, which can inhibit the formation of kidney stones by inhibiting high urinary calcium. ^[1]