Tritazide

Uses

Indicated for the treatment of mild to moderate hypertension in patients (in whom combination therapy is appropriate) who have been stabilised on the individual components given in the same proportion.

Tritazide is also used to associated treatment for these conditions: Acidosis, Renal Tubular, Calcium Nephrolithiasis, Cirrhosis of the Liver, Congestive Heart Failure (CHF), Diabetes Insipidus, Edema, High Blood Pressure (Hypertension), Hypertension,Essential, Hypokalemia caused by diuretics, Nephrotic Syndrome, Premenstrual tension with edema, Sodium retention, Stroke, Prophylaxis of preeclampsiaCardiovascular Events, Diabetic Nephropathy, Heart Failure, Heart Failure With Reduced Ejection Fraction (HFrEF), High Blood Pressure (Hypertension), Myocardial Infarction, Nondiabetic proteinuric chronic kidney disease, Stroke, High risk cardiovascular event

How Tritazide works

Hydrochlorothiazide is transported from the circulation into epithelial cells of the distal convoluted tubule by the organic anion transporters OAT1, OAT3, and OAT4. From these cells, hydrochlorothiazide is transported to the lumen of the tubule by multidrug resistance associated protein 4 (MRP4).

Normally, sodium is reabsorbed into epithelial cells of the distal convoluted tubule and pumped into the basolateral interstitium by a sodium-potassium ATPase, creating a concentration gradient between the epithelial cell and the distal convoluted tubule that promotes the reabsorption of water.

Hydrochlorothiazide acts on the proximal region of the distal convoluted tubule, inhibiting reabsorption by the sodium-chloride symporter, also known as Solute Carrier Family 12 Member 3 (SLC12A3). Inhibition of SLC12A3 reduces the magnitude of the concentration gradient between the epithelial cell and distal convoluted tubule, reducing the reabsorption of water.

Ramipril inhibits the RAAS system by binding to and inhibiting ACE thereby preventing the conversion of angiotensin I to angiotensin II. As plasma levels of angiotensin II fall, less activation of the G-protein coupled receptors angiotensin receptor I (AT₁R) and angiotensin receptor II (AT₂R) occurs.

AT₁R mediates vasoconstriction, inflammation, fibrosis, and oxidative stress through a variety of signaling pathways. These include G_q coupling to the inositol triphosphate pathway, activation of phospholipases C, A₂, and D which contribute to eicosanoid production, activation of Ca^{2+ These counteracting effects are shared by the Mas receptor which is activated by Ang(1-7), a subtype of angiotensin produced by plasma esterases from AngI or by ACE2 from AngII produced through a secondary pathway by tonin and cathepsin G. Ang(1-7) also activates AT₂R although the bulk of its effect is mediated by MasR.}

ACE is also responsible for the breakdown of bradykinin. The resulting buildup of bradykinin due to ACE inhibition is thought to mediate the characteristic dry-cough as a side effect of ACE inhibitor medications.

Dosage

Tritazide dosage

Dose Titration Guided by Clinical Effect. A patient whose blood pressure is not adequately controlled with ramipril (or another ACE inhibitor) alone or with hydrochlorothiazide (or another thiazide diuretic) alone may be switched to combination therapy with Ramipril 2.5 mg + Hydrochlorothiazide 12.5 mg or Ramipril 5 mg + Hydrochlorothiazide 25 mg tablet.

Replacement Therapy: For convenience, patients receiving ramipril and hydrochlorothiazide from separate tablets may instead wish to receive tablets of combination of Ramipril 2.5 mg + Hydrochlorothiazide 12.5 mg or Ramipril 5 mg + Hydrochlorothiazide 25 mg. If necessary, the dose may be increased to two tablets of Ramipril 2.5 mg + Hydrochlorothiazide 12.5 mg or Ramipril 5 mg + Hydrochlorothiazide 25 mg once daily.

Maximum daily dose: 10 mg ramipril and 50 mg hydrochlorothiazide (four tablets of Ramipril 2.5 mg + Hydrochlorothiazide 12.5 mg or two tablets of Ramipril 5 mg + Hydrochlorothiazide 25 mg).

Side Effects

The combination of Ramipril and Hydrochlorothiazide is generally well tolerated. Side effects commonly reported include headache, dizziness, asthenia, nausea, vomiting, hypotension, cough, weakness, diarrhoea, fever, gastric irritation, pulmonary oedema, photosensitivity, electrolyte imbalance, hyperglycaemia, hyperuricaemia and vertigo.

Toxicity

The oral LD₅₀ of hydrochlorothiazide is >10g/kg in mice and rats.

Patients experiencing an overdose may present with hypokalemia, hypochloremia, and hyponatremia. Treat patients with symptomatic and supportive treatment including fluids and electrolytes. Vasopressors may be administered to treat hypotension and oxygen may be given for respiratory impairment.

Symptoms of overdose may include excessive peripheral vasodilation (with marked hypotension and shock), bradycardia, electrolyte disturbances, and renal failure. Cases of ACE inhibitor induced hepatotoxicity have been reported in humans and presented as acute jaundice and elevated liver enzymes. Removal of the ACE inhbitor resulted in a decline in liver enzymes and re-challenge produced a subsequent increase.

There were no observed tumerogenic effects at chronic doses up to 500mg/kg/day to rats for 24 months or at doses up to 1000mg/kg/day to mice for 18 months. For both species doses were administered by gavage and equivalent to 200 time the maximum recommended human exposure based on body surface area.

No mutagenic activity was detected in the Ames test in bacteria, the micronucleus test in mice, unscheduled DNA synthesis in a human cell line, or a forward gene-mutation assay in a Chinese hamster ovary cell line. Several metabolites of ramipril also produced negative results in the Ames test.

No effects on fertility were seen in rats at doses up to 500mg/kg/day. No teratogenicity was observed in rats and cynomolgus monkeys at doses 400 times the maximum recommended human exposure nor in rabbites at 2 times the maximum recommended human exposure.

LD₅₀ 10 g/kg (rat). LD₅₀ 10.5 g/kg (mouse). LD₅₀ 1 g/kg (dog).

Precaution

Treatment with Ramipril and Hydrochlorothiazide combination requires regular medical supervision. Generally dehydration, reduced blood volume (hypovolumia) or salt depletion should be corrected before initiating the treatment (in patients with concomitant heart failure, however, this must be carefully weighed against the risk of volume overload).

Special caution is necessary during the treatment of: Patients with severe and particularly with malignant hypertension. Patients with concomitant and particularly with severe heart failure. Patients in whom fluid or salt deficiency exists or may develop (as a result of inadequate fluid or salt intake) or as a result of diarrhoea, vomiting or excessive sweating in cases where salt and fluid replacement is inadequate. Patients with haemodynamically relevant renal artery stenosis. In patients with pre-existing impairment of renal function or in kidney transplant patients. White blood cell count should be monitored (more frequent in the initial phase of the treatment) so that leucopenia can be detected. Insufficient experience has been gained concerning the use of Ramipril and Hydrochlorothiazide combination in children.

Interaction

Combination with diuretics or other antihypertensive agents or nitrates and tricyclic antidepressants may potentiate the antihypertensive response to Ramipril and Hydrochlorothiazide combination. Patients previously treated with diuretics may experience a marked drop in blood pressure. Ramipril / Hydrochlorothiazide may weaken the effectiveness of blood sugar lowering medications (antidiabetic agents, e.g. insulin and sulphonylurea derivatives). When Ramipril/Hydrochlorothiazide is administered simultaneously with acetyl salicylic acid or indomethacin, attenuation of antihypertensive effect and moreover acute renal failure may occur. Ramipril / Hydrochlorothiazide may potentiate the effects of alcohol.

Volume of Distribution

The volume of distribution varies widely from one study to another with values of 0.83-4.19L/kg.

Elimination Route

An oral dose of hydrochlorothiazide is 65-75% bioavailable, with a T_max of 1-5 hours, and a C_max of 70-490ng/mL following doses of 12.5-100mg. When taken with a meal, bioavailability is 10% lower, C_max is 20% lower, and T_max increases from 1.6 to 2.9 hours.

The extent of absorption is at least 50-60%.. Food decreases the rate of absorption from the GI tract without affecting the extent of absorption. The absolute bioavailabilities of ramipril and ramiprilat were 28% and 44%, respectively, when oral administration was compared to intravenous administration. The serum concentration of ramiprilat was unchanged when capsules were opened and the contents dissolved in water, dissolved in apple juice, or suspended in apple sauce.

Half Life

The plasma half life of hydrochlorothiazide is 5.6-14.8h.

Plasma concentrations of ramiprilat decline in a triphasic manner. Initial rapid decline represents distribution into tissues and has a half life of 2-4 hours. The half life of the apparent elimination phase is 9-18 hours, which is thought to represent clearance of free drug. The half-life of the terminal elimination phase is > 50 hours and thought to represent clearance of drug bound to ACE due to its slow dissociation. The half life of ramiprilat after multiple daily doses (MDDs) is dose-dependent, ranging from 13-17 hours with 5-10 mg MDDs to 27-36 hours for 2.5 mg MDDs.

Clearance

The renal clearance of hydrochlorothiazide in patients with normal renal function is 285mL/min. Patients with a creatinine clearance of 31-80mL/min have an average hydroxychlorothiazide renal clearance of 75mL/min, and patients with a creatinine clearance of ≤30mL/min have an average hydroxychlorothiazide renal clearance of 17mL/min.

The renal clearance of ramipril and ramiprilat was reported to be 7.2 and 77.4 mL/min/1.73m². The mean renal clearance of ramipril and ramiprilat is reported to be 10.7 and 126.8 mL/min in healthy elderly patients with normal renal function, additionally the Cmax of ramiprilat is approximately 20% higher in this population. While the pharmacokinetics of ramipril appear unaffected by reduced renal function, the plasma concentration and half-life of ramiprilat are increased. In patient's with hepatic failure the concentration of ramipril is initially increased while the tmax of ramiprilat is prolonged due to a reduced ability to metabolize the drug. However, steady state concentrations of ramiprilat are the same in hepatic failure as in healthy patients.

Elimination Route

Hydrochlorothiazide is eliminated in the urine as unchanged hydrochlorothiazide.

Following oral administration, about 60% of the dose is eliminated in the urine as unchanged ramipril (6

Pregnancy & Breastfeeding use

ACE inhibitors can cause foetal and neonatal morbidity and death when administered to pregnant women. Also, thiazides cross the placental barrier and appear in cord blood. There is a risk of foetal or neonatal jaundice, thrombocytopenia, and possibly other adverse reactions that have occurred in adults. When pregnancy is detected, Ramipril and Hydrochlorothiazide combination should be discontinued as soon as possible. Tritazide is excreted in breast milk. Because of the potential for serious adverse reactions in nursing infants, women receiving Ramipril and Hydrochlorothiazide combination should not breast feed.

Contraindication

Tritazide must not be used in patients with hypersensitivity to ramipril, hydrochlorothiazide or other thiazide diuretics. History of hereditary angioneurotic oedema. Severe impairment of renal function. Haemodynamically relevant unilateral or bilateral renal artery stenosis, mitral stenosis, aortic stenosis, and in patients with low blood pressure (hypotensive patients) or in patients with an unstable circulatory situation (haemodynamically unstable patients) where there might be a risk of life-threatening fall in blood pressure and renal failure. Clinically relevant electrolyte disturbances e.g. hypokalemia, hyponatremia or hypercalcemia which may worsen following treatment.

Special Warning

Dosage in renal impairment: In patients with a creatinine clearance between 60 and 30 ml/min, treatment should be initiated with Ramipril 1.25 mg monotherapy. If blood pressure is not adequately controlled, the dose of Ramipril may be increased to 2.5 mg. If blood pressure is still not controlled, patient may be switched to one tablet of Ramoril 2.5 Plus once daily. Dosage may be titrated upward to Ramoril 5 Plus until blood pressure is controlled.

Use in children: Safety and effectiveness in paediatric patients have not been established

Acute Overdose

Ramipril: Limited data on human overdosage are available. The most likely clinical manifestations would be symptoms attributable to hypotension. Because the hypotensive effect of Ramipril is achieved through vasodilation and effective hypovolemia, it is reasonable to treat Ramipril overdosage by infusion of normal saline solution.

Hydrochlorothiazide: The most common signs and symptoms observed are those caused by electrolyte depletion (hypokalemia, hypochloremia, and dehydration resulting from excessive diuresis. If digitalis has also been administered, hypokalemia, may accentuate cardiac arrhythmias. The degree to which Hydrochlorothiazide is removed by hemodialysis has not been established.

Storage Condition

Store in a cool and dry place, protected from light.

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