Aliskiren and hydrochlorothiazide

Uses

Treating high blood pressure. It may be used alone or with other medicines. Aliskiren is a direct renin inhibitor. It works by relaxing blood vessels, which lowers blood pressure and helps the heart to pump blood more easily.

Hydrochlorothiazide is used for-

• Edema associated with congestive heart failure, hepatic cirrohosis, various forms of renal dysfunction and corticosteroid and estrogen therapy
• Management of hypertension either as the sole therapeutic agent or to enhance the effectiveness of other antihypertensive drugs in the more severe form of hypertension
• Management of diabetes insipidus
• Management of proximal renal tubular acidosis
• Idiopathic hypercalciuria and calcium nephrolithiasis, osteoporosis and exercise induced hyperkalemia

Aliskiren and hydrochlorothiazide is also used to associated treatment for these conditions: High Blood Pressure (Hypertension)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 preeclampsia

How Aliskiren and hydrochlorothiazide works

Aliskiren is a renin inhibitor. Renin is secreted by the kidneys when blood volume and renal perfusion decrease. It normally cleaves the protein angiotensinogen to form angiotensin I. Angiotensin I is then converted to angiotensin II, an active protein. Angiotensin II is a potent vasoconstrictor that causes the release of catecholamines into the circulation. It also promotes the secretion of aldosterone in addition to sodium reabsorption, increasing blood pressure. Additionally, angiotensin II acts on the adrenal cortex where it stimulates aldosterone release. Aldosterone increases sodium reabsorption and potassium excretion in the nephron.

Aliskiren prevents the above process via binding to renin at its active site, stopping the cleavage of angiotensin, in turn inhibiting the formation of angiotensin I. This ends the cascade of angiotensin II mediated mechanisms that normally increase blood pressure.

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.

Dosage

Aliskiren and hydrochlorothiazide dosage

Initial adult dose: 150 mg orally once a day.

Maintenance adult dose: The dosage may be increased to 300 mg daily if blood pressure is not adequately controlled. No dosage adjustment is recommended based on gender, age, body weight or race.

Safety and efficacy have not been established in patients younger than 18 years. AUC is increased in elderly patients 65 years of age and older.

Adults-

For Edema: The usual adult dosage is 25 to 100 mg daily as a single or divided dose.

For Control of Hypertension: The usual initial dose in adults is 25 mg daily given as a single dose. The dose may be increased to 50 mg daily, given as a single or two divided doses. Doses above 50 mg are often associated with marked reductions in serum potassium. In some patients (especially the elderly) an initial dose of 12.5 mg daily may be sufficient.

Infants and children-

For diuresis and for control of hypertension: The usual pediatric dosage is 1 to 2 mg/kg/day in single or two divided doses, not to exceed 37.5 mg per day in infants up to 2 years of age or 100 mg per day in children 2 to 12 years of age. In infants less than 6 months of age, doses up to 3 mg/kg/day in two divided doses may be required.

Side Effects

Skin rash (1%), Diarrhea (2%), Increased creatine phosphokinase, Increased blood urea nitrogen (≤7%), increased serum creatinine (≤7%), RespirCough (1%)

Limited to important or life-threatening: Anaphylaxis, decreased hematocrit, decreased hemoglobin, gastroesophageal reflux disease, hepatic insufficiency, hyperkalemia, increased uric acid, nausea, rhabdomyolysis, seizure, severe hypotension, Stevens-Johnson syndrome, tonic-clonic seizures, vomiting

Generally, Hydrochlorothiazide is well tolerated. However, a few side effects may occur like weakness, restlessness, dizziness, headache, fever, diarrhea, vomiting, sialadenitis, cramping, constipation, gastric irritation, nausea, anorexia, and hypotension. In rare case hyperglycemia, glycosuria, hyperuricemia and muscle spasm may occur.

Toxicity

The oral LD50 of aliskiren in rats is >2000 mg/kg. Overdose information is limited in the literature, however, an overdose with aliskiren is likely to result in hypotension. Supportive treatment should be initiated in the case of an overdose.

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.

Precaution

Thiazides should be used with caution in patients with severe renal disease, impaired hepatic function or progressive liver disease and gout.

Interaction

Major: Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.

Moderate: Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.

Minor: Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.

Alcohol, Barbiturates, or Narcotics: Potentiation of orthostatic hypotension may occur.

Antidiabetic Drugs (oral agents and insulin): Thiazides can impair control of diabetes mellitus by diet and antidiabetic Drugs. Antihypertensive Drugs: Additive effect or potentiation.

Volume of Distribution

Unchanged aliskiren accounts for about 80% of the drug found in the plasma.

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

Elimination Route

Aliskiren is absorbed in the gastrointestinal tract and is poorly absorbed with a bioavailability between 2.0 and 2.5%. Peak plasma concentrations of aliskiren are achieved between 1 to 3 hours after administration. Steady-state concentrations of aliskiren are achieved within 7-8 days of regular administration.

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.

Half Life

Plasma half-life for aliskiren can range from 30 to 40 hours with an accumulation half-life of about 24 hours.

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

Clearance

Aliskiren is partially cleared in the kidneys, and safety data have not been established for patients with a creatinine clearance of less than 30 mL/min. One pharmacokinetic study revealed an average renal clearance of 1280 +/- 500 mL/hour in healthy volunteers.

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.

Elimination Route

Aliskiren is mainly excreted via the hepatobiliary route and by oxidative metabolism by hepatic cytochrome enzymes. Approximately one-quarter of the absorbed dose appears in the urine as unchanged parent drug. One pharmacokinetic study of radiolabeled aliskiren detected 0.6% radioactivity in the urine and more than 80% in the feces, suggesting that aliskiren is mainly eliminated by the fecal route.

Hydrochlorothiazide is eliminated in the urine as unchanged hydrochlorothiazide.

Pregnancy & Breastfeeding use

If pregnancy is detected, discontinue aliskiren as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus.

Pregnancy: Evidence of fetal risk in hydrochlorothiazide therapy is found, but it is indicated if benefits outweigh risks. Thiazides are indicated in pregnancy when edema is due to pathologic causes.\

Lactation: Neonatal side effects have been seen incase of hydrochlorothiazide therapy and therefore it is not recommended.

Contraindication

Hypersensitivity to aliskiren or any component of the formulation; concomitant use with an ACE inhibitor or ARB in patients with diabetes mellitus History of angioedema with aliskiren, ACE inhibitors, or ARBs; hereditary or idiopathic angioedema; pregnancy, breast-feeding; concomitant use with ACE inhibitors or ARBs in patients with GFR <60 mL/minute/1.73 m2; patients <2 years of age.

Hydrochlorothiazide is contraindicated to the patients of anuria and those who are sensitive to hydrochlorothiazide or to other sulfonamide-derived drugs. Therapy is not to be initiated in diabetes mellitus.

Special Warning

Renal Dose Adjustments:

• Mild to moderate renal dysfunction (CrCl 30 mL/min or greater): No adjustment recommended.
• Severe renal dysfunction (CrCl 30 mL/min or less): Not recommended

Liver Dose Adjustments

: No adjustment recommended

Elderly: in some patients specially the elderly an initial dose of 12.5 mg daily may be sufficient.

Children: An initial dose for children has been 1 to 2 mg per kg body-weight in 2 divided doses. Infants under 6 months may need doses upto 3 mg per kg daily.

Acute Overdose

The most common signs and symptoms observed are those caused by electrolyte depletion (hypokalemia, hypochloremia, hyponatremia) and dehydration resulting from excessive diuresis. Rarely, autoimmune hemolytic anemia and other hypersensitivity reactions may complicate the picture.

In the event of over dosage, symptomatic and supportive measures should be employed. Emesis should be induced or gastric lavage performed. Correct dehydration, electrolyte imbalance, hepatic coma and hypotension by established procedures. Hemodialysis can be used successfully to treat severe intoxication.

Storage Condition

Store aliskiren at room temperature, between 15° to 30° C. Store in the original bottle, away from heat, moisture, and light. Keep aliskiren out of the reach of children and away from pets.

Store between 15-30°C. Protect from light, moisture and freezing.

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