TELSTAN-H 80/25 TABLET 80MG/25MG

Telmisartan
Hydrochlorothiazide

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

4'-((1,4'-Dimethyl-2'-propyl(2,6'-bi-1H-benzimidazol)-1'-yl)methyl)-(1,1'-biphenyl)-2-carboxylic acid | 4'-((4-Methyl-6-(1-methyl-2-benzimidazolyl)-2-propyl-1-benzimidazolyl)methyl)-2-biphenylcarboxylic acid | 4'-[(1,4'-Dimethyl-2'propyl[2,6'-bi-1H-benzimidazol]-1'-yl)methyl]-[1,1'-biphenyl]-2-carboxylic acid | 4'-[(1,7'-Dimethyl-2'-propyl-1H,3'h-2,5'-bibenzimidazol-3'-yl)methyl]biphenyl-2-carboxylic acid | BIBR 277 | Telmisartan | Telmisartan |

Description

Telmisartan is an angiotensin II receptor antagonist (ARB) used in the management of hypertension. Generally, angiotensin II receptor blockers (ARBs) such as telmisartan bind to the angiotensin II type 1 (AT1) receptors with high affinity, causing inhibition of the action of angiotensin II on vascular smooth muscle, ultimately leading to a reduction in arterial blood pressure. Recent studies suggest that telmisartan may also have PPAR-gamma agonistic properties that could potentially confer beneficial metabolic effects.

Indication

Used alone or in combination with other classes of antihypertensives for the treatment of hypertension. Also used in the treatment of diabetic nephropathy in hypertensive patients with type 2 diabetes mellitus, as well as the treatment of congestive heart failure (only in patients who cannot tolerate ACE inhibitors).

Mechanism of Action

Telmisartan interferes with the binding of angiotensin II to the angiotensin II AT1-receptor by binding reversibly and selectively to the receptors in vascular smooth muscle and the adrenal gland. As angiotensin II is a vasoconstrictor, which also stimulates the synthesis and release of aldosterone, blockage of its effects results in decreases in systemic vascular resistance. Telmisartan does not inhibit the angiotensin converting enzyme, other hormone receptors, or ion channels. Studies also suggest that telmisartan is a partial agonist of PPARγ, which is an established target for antidiabetic drugs. This suggests that telmisartan can improve carbohydrate and lipid metabolism, as well as control insulin resistance without causing the side effects that are associated with full PPARγ activators.

Pharmacodynamics

Telmisartan is an orally active nonpeptide angiotensin II antagonist that acts on the AT1 receptor subtype. It has the highest affinity for the AT1 receptor among commercially available ARBS and has minimal affinity for the AT2 receptor. New studies suggest that telmisartan may also have PPARγ agonistic properties that could potentially confer beneficial metabolic effects, as PPARγ is a nuclear receptor that regulates specific gene transcription, and whose target genes are involved in the regulation of glucose and lipid metabolism, as well as anti-inflammatory responses. This observation is currently being explored in clinical trials. Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin-converting enzyme (ACE, kininase II). Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation, and renal reabsorption of sodium. Telmisartan works by blocking the vasoconstrictor and aldosterone secretory effects of angiotensin II.

Pharmacokinetics

Absorption:

Absolute bioavailability depends on dosage. Food slightly decreases the bioavailability (a decrease of about 6% is seen when the 40-mg dose is administered with food).

Distribution:

* 500 L

Metabolism:

Minimally metabolized by conjugation to form a pharmacologically inactive acylglucuronide; the glucuronide of the parent compound is the only metabolite that has been identified in human plasma and urine. The cytochrome P450 isoenzymes are not involved in the metabolism of telmisartan.

Elimination:

Following either intravenous or oral administration of 14C-labeled telmisartan, most of the administered dose (>97%) was eliminated unchanged in feces via biliary excretion; only minute amounts were found in the urine (0.91% and 0.49% of total radioactivity, respectively).

Half-life

Bi-exponential decay kinetics with a terminal elimination half-life of approximately 24 hours.

Clearance

* >800 mL/min

Toxicity

Intravenous LD50 in rats is 150-200 mg/kg in males and 200 to 250 mg/kg in females. Acute oral toxicity is low: no deaths and no changes occurred in rats or dogs at 2000 mg/kg, the highest dose tested. Limited data are available with regard to overdosage in humans. The most likely manifestations of overdosage with telmisartan would be hypotension, dizziness and tachycardia; bradycardia could occur from parasympathetic (vagal) stimulation.

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

HCTZ | Hydrochlorothiazide |

Description

A thiazide diuretic often considered the prototypical member of this class. It reduces the reabsorption of electrolytes from the renal tubules. This results in increased excretion of water and electrolytes, including sodium, potassium, chloride, and magnesium. It has been used in the treatment of several disorders including edema, hypertension, diabetes insipidus, and hypoparathyroidism. [PubChem]

Indication

For the treatment of high blood pressure and management of edema.

Mechanism of Action

Hydrochlorothiazide, a thiazide diuretic, inhibits water reabsorption in the nephron by inhibiting the sodium-chloride symporter (SLC12A3) in the distal convoluted tubule, which is responsible for 5% of total sodium reabsorption. Normally, the sodium-chloride symporter transports sodium and chloride from the lumen into the epithelial cell lining the distal convoluted tubule. The energy for this is provided by a sodium gradient established by sodium-potassium ATPases on the basolateral membrane. Once sodium has entered the cell, it is transported out into the basolateral interstitium via the sodium-potassium ATPase, causing an increase in the osmolarity of the interstitium, thereby establishing an osmotic gradient for water reabsorption. By blocking the sodium-chloride symporter, hydrochlorothiazide effectively reduces the osmotic gradient and water reabsorption throughout the nephron.

Pharmacodynamics

Thiazides such as hydrochlorothiazide promote water loss from the body (diuretics). They inhibit Na+/Cl- reabsorption from the distal convoluted tubules in the kidneys. Thiazides also cause loss of potassium and an increase in serum uric acid. Thiazides are often used to treat hypertension, but their hypotensive effects are not necessarily due to their diuretic activity. Thiazides have been shown to prevent hypertension-related morbidity and mortality although the mechanism is not fully understood. Thiazides cause vasodilation by activating calcium-activated potassium channels (large conductance) in vascular smooth muscles and inhibiting various carbonic anhydrases in vascular tissue.

Pharmacokinetics

Absorption:

50-60%

Distribution:

Not Available

Metabolism:

Hydrochlorothiazide is not metabolized.

Elimination:

Hydrochlorothiazide is not metabolized but is eliminated rapidly by the kidney. Hydrochlorothiazide crosses the placental but not the blood-brain barrier and is excreted in breast milk.

Half-life

5.6 and 14.8 hours

Clearance

Not Available

Toxicity

The most common signs and symptoms observed are those caused by electrolyte depletion (hypokalemia, hypochloremia, hyponatremia) and dehydration resulting from excessive diuresis. If digitalis has also been administered, hypokalemia may accentuate cardiac arrhythmias. The oral LD50 of hydrochlorothiazide is greater than 10 g/kg in the mouse and rat.

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

TELSTAN-H 80/25 TABLET 80MG/25MG was registered with Health Science Authority of Singapore by THINQ PHARMA - CRO PTE LTD. It is marketed with the registration number of SIN15091P with effective from 2016-09-28.

This product contains 80mg of Telmisartan, and 25mg of Hydrochlorothiazide in the form of ORAL TABLET.

The medicine was manufactured by Alembic Pharmaceuticals LTD in INDIA

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Anatomical Therapeutic Chemical (ATC) Classification

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