Thiazides

Thiazide diuretics are also used to treat hypertension (high blood pressure) and oedema (such as that caused by heart, liver, or kidney disease).  The members of this class of diuretics are derived from benzothiadiazine. The term "thiazide" is also often used for drugs with a similar action that do not have the thiazide chemical structure.  These agents are more properly termed ‘thiazide-like diuretics’.

Their mechanism of action is not dissimilar to the loop diuretics, the major difference being the site of activity. They too inhibit reabsorption of sodium (Na⁺) and chloride (Cl^-) ions from the distal convoluted tubules in the kidneys but by blocking the thiazide-sensitive Na⁺-Cl^- symporter.

Again, by disrupting the reabsorption of ions, the fluid leaving the kidney is more ‘concentrated’ and there is an ‘osmotic driving force’ to dilute it as it leaves the collecting duct system, ultimately resulting in increased urine production and reduction of water in the body.

There is a difference however in the effects, although ultimately one can still classify it as an electrolyte imbalance. 

This class of drugs tend to decrease the amount of calcium lost in the urine, [lower urinary calcium excretion] . This effect, according to the drug marketing literature “ is associated with an increase in bone mineral density and reductions in fracture rates attributable to osteoporosis” although it is unclear from the descriptions how this is supposed to happen.  One would have thought that an unnatural  retention of calcium in the kidneys would lead to kidney stones [but then who am I to judge] and hypercalcemia [which is a recognised side effect] .

This class of drugs has also been used to treat diabetes insipidus, “the effect of thiazide diuretics is presumably[sic]  mediated by a hypovolemia-induced increase in proximal sodium and water reabsorption, thereby diminishing water delivery to the ADH-sensitive sites in the collecting tubules and reducing the urine output”.  So they don’t really know how it works but they use it anyway.

Thiazides also cause loss of potassium which is serious [hypokalemia].  They can result in a loss of magnesium – also serious [Hypomagnesemia].  They reduce the clearance of uric acid and can cause gout. They can decrease placental perfusion and adversely affect the fetus.  Other known side effects include

• Hyperglycemia – high blood sugar
• Hyperlipidemia
• Hyponatremia
• Postural hypotension
• Impaired glucose tolerance
• Impotence
• Headache
• Nausea/vomiting
• Photosensitivity
• Weight Gain

When administered acutely thiazides lower blood pressure by causing diuresis, a fall in plasma volume and a reduction in cardiac output. However, after chronic use thiazides cause a reduction in blood pressure by lowering peripheral resistance (i.e. vasodilation).

Drugs

This list is likely to change over time, but at least it provides you with an idea of which drugs come within which category.  The drugs which have caused hallucinations according to the ehealthme web site are listed separately under the observations whereas those in this list without any figures have no record on this site.

• Bendroflumethiazide, formerly bendrofluazide, is used to treat hypertension.  It is also a fairly cheap drug, made cheap through mass production.  It works by inhibiting sodium absorption at the beginning of the distal convoluted tubule (DCT).

• Chlorothiazide sodium (Diuril) is used within the hospital setting or for personal use to manage excess fluid associated with congestive heart failure. It is also used as an antihypertensive.  Most often taken in pill form, it is usually taken orally once or twice a day.

• Chlortalidone [2]  or chlorthalidone is used to treat hypertension, originally marketed as Hygroton. It is a thiazide-like diuretic because it acts similarly to the thiazides but does not contain the benzothiadiazine molecular structure. Compared with other medications of the thiazide class, chlorthalidone has the longest duration of action, but a similar diuretic effect at maximal therapeutic doses. It is used in the management of hypertension and edema.

• Clofenamide (or diumide) is a thiazide like drug

• Clorexolone is a thiazide like drug

• Clopamide is categorised as a thiazide like drug

• Cyclopenthiazide.

• Cyclothiazide (Anhydron, Acquirel, Doburil, Fluidil, Renazide, Tensodiural, Valmiran) is a thiazide diuretic and antihypertensive that was originally introduced in 1963 In 1993, it was discovered that cyclothiazide is a positive allosteric modulator of the AMPA receptor, capable of reducing or essentially eliminating rapid desensitization of the receptor. Additionally, in 2003, cyclothiazide was also found to act as a GABA_A receptor negative allosteric modulator, potently inhibiting GABA_A-mediated currents.

• Dyazide [45] -  is the brand name for a drug used to treat hypertension (high blood pressure) and edema (water retention), which is a combination of triamterene and hydrochlorothiazide.

• Fenquizone is a thiazide like diuretic, used primarily in the treatment of treatment of oedema and hypertension

• Hydrochlorothiazide [56a + 61b = 117]  -  see the detailed observation for more details.

• Indapamide [2]  is used in the treatment of hypertension, as well as decompensated cardiac failure. The US trade name for indapamide is Lozol. Indapamide is marketed as Natrilix outside of the US. It is described as a thiazide-like diuretic

• Hydroflumethiazide (or Saluron).

• Mefruside is a thiazide like diuretic indicated for the treatment of edema and hypertension, sold under the tradename Baycaron

• Mebutizide

• Methyclothiazide

• Meticrane is athiazide like drug

• Metolazone is a thiazide-like diuretic marketed under the brand names Zytanix, Zaroxolyn [16] , and Mykrox. It is primarily used to treat congestive heart failure and high blood pressure.

• Polythiazide

• Quinethazone brand name Hydromox is a thiazide like diuretic used to treat hypertension. Common side effects include dizziness, dry mouth, nausea, and low potassium levels

• Trichlormethiazide  [2]  - currently being sold under the brand names of Achletin, Diu-Hydrin and Triflumen,  is a diuretic with properties similar to those of hydrochlorothiazide. 

• Xipamide is a sulfonamide thiazine like drug marketed under the trade names Aquaphor and Aquaphoril,  used for the treatment of oedema and hypertension.