Olmesartan Medoxomil and Hydrochlorothiazide: Package Insert and Label Information (Page 2 of 3)

7 DRUG INTERACTIONS

7.1 Agents Increasing Serum Potassium

Coadministration of olmesartan medoxomil and hydrochlorothiazide with other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients.

7.2 Lithium

Increases in serum lithium concentrations and lithium toxicity have been reported during concomitant administration of lithium with angiotensin II receptor antagonists or hydrochlorothiazide. Monitor serum lithium levels during concomitant use.

7.3 Non-Steroidal Anti-Inflammatory Agents including Selective Cyclooxygenase-2 Inhibitors (COX-2 Inhibitors)

Olmesartan medoxomil
In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, co-administration of NSAIDs, including selective COX-2 inhibitors, with angiotensin II receptor antagonists (including olmesartan medoxomil) may result in deterioration of renal function, including possible acute renal failure. These effects are usually reversible. Monitor renal function periodically in patients receiving olmesartan medoxomil and NSAID therapy.
The antihypertensive effect of angiotensin II receptor antagonists, including olmesartan medoxomil may be attenuated by NSAIDs including selective COX-2 inhibitors.
Hydrochlorothiazide
In some patients the administration of a NSAID can reduce the diuretic, natriuretic, and antihypertensive effects of thiazide diuretics. Therefore, monitor blood pressure closely.

7.4 Dual Blockade of the Renin Angiotensin System

Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy. Most patients receiving the combination of two RAS inhibitors do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAS inhibitors. Closely monitor blood pressure, renal function and electrolytes in patients on olmesartan medoxomil and hydrochlorothiazide and other agents that affect the RAS.
Do not co-administer aliskiren with olmesartan medoxomil and hydrochlorothiazide in patients with diabetes [see Contraindications (4)]. Avoid use of aliskiren with olmesartan medoxomil and hydrochlorothiazide in patients with renal impairment (GFR <60 mL/min).

7.5 Colesevelam Hydrochloride

Concurrent administration of bile acid sequestering agent colesevelam hydrochloride reduces the systemic exposure and peak plasma concentration of olmesartan. Administration of olmesartan at least 4 hours prior to colesevelam hydrochloride decreased the drug interaction effect. Consider administering olmesartan at least 4 hours before the colesevelam hydrochloride dose [see Clinical Pharmacology (12.3)].

7.6 The Use of Hydrochlorothiazide with Other Drugs

When administered concurrently the following drugs may interact with thiazide diuretics:
Antidiabetic drugs (oral agents and insulin): Dosage adjustment of the antidiabetic drug may be required.
Ion exchange resins: Staggering the dosage of hydrochlorothiazide and ion exchange resins (e.g., cholestyramine, colestipol) such that hydrochlorothiazide is administered at least 4 hours before or 4 to 6 hours after the administration of resins would potentially minimize the interaction [see Clinical Pharmacology (12.3)].
Corticosteroids, ACTH: Intensified electrolyte depletion, particularly hypokalemia.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category D
Use of drugs that act on the renin-angiotensin system during the second and third trimesters of pregnancy reduces fetal renal function and increases fetal and neonatal morbidity, and death. Resulting oligohydramnios can be associated with fetal lung hypoplasia and skeletal deformations. Potential neonatal adverse effects include skull hypoplasia, anuria, hypotension, renal failure, and death. When pregnancy is detected, discontinue olmesartan medoxomil and hydrochlorothiazide as soon as possible. These adverse outcomes are usually associated with use of these drugs in the second and third trimester of pregnancy. Most epidemiologic studies examining fetal abnormalities after exposure to antihypertensive use in the first trimester have not distinguished drugs affecting the renin-angiotensin system from other antihypertensive agents. Appropriate management of maternal hypertension during pregnancy is important to optimize outcomes for both mother and fetus.
In the unusual case that there is no appropriate alternative to therapy with drugs affecting the renin-angiotensin system for a particular patient, apprise the mother of the potential risk to the fetus. Perform serial ultrasound examinations to assess the intraamniotic environment. If oligohydramnios is observed, discontinue olmesartan medoxomil and hydrochlorothiazide, unless it is considered lifesaving for the mother. Fetal testing may be appropriate, based on the week of pregnancy. Patients and physicians should be aware, however, that oligohydramnios may not appear until after the fetus has sustained irreversible injury. Closely observe infants with histories of in utero exposure to olmesartan medoxomil and hydrochlorothiazide for hypotension, oliguria, and hyperkalemia [see Use in Specific Populations (8.4)].

8.3 Nursing Mothers

It is not known whether olmesartan is excreted in human milk, but olmesartan is secreted at low concentration in the milk of lactating rats. Thiazides appear in human milk. Because of the potential for adverse effects on the nursing infant, a decision should be made whether to discontinue nursing or discontinue olmesartan medoxomil and hydrochlorothiazide, taking into account the importance of the drug to the mother.

8.4 Pediatric Use

Neonates with a history of in utero exposure to olmesartan medoxomil and hydrochlorothiazide:
If oliguria or hypotension occurs, direct attention toward support of blood pressure and renal perfusion. Exchange transfusions or dialysis may be required as a means of reversing hypotension and substituting for disordered renal function.
Safety and effectiveness of olmesartan medoxomil and hydrochlorothiazide in pediatric patients have not been established.

8.5 Geriatric Use

Clinical studies of olmesartan medoxomil and hydrochlorothiazide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function and of concomitant diseases or other drug therapy.
Olmesartan and hydrochlorothiazide are substantially excreted by the kidney, and the risk of toxic reactions to olmesartan medoxomil and hydrochlorothiazide may be greater in patients with impaired renal function.

8.6 Renal Impairment

Safety and effectiveness of olmesartan medoxomil and hydrochlorothiazide in patients with severe renal impairment (CrCl ≤ 30 mL/min) have not been established. No dose adjustment is required in patients with mild (CrCl 60 to 90 mL/min) or moderate (CrCl 30 to 60) renal impairment.

8.7 Hepatic Impairment

Olmesartan medoxomil
No dose adjustment is necessary for patients with mild-to-severe liver disease.
Hydrochlorothiazide
Minor alterations of fluid and electrolyte balance may precipitate hepatic coma in patients with impaired hepatic function or progressive liver disease.

10 OVERDOSAGE

Olmesartan medoxomil
Limited data are available related to overdosage of olmesartan medoxomil in humans. The most likely manifestations of overdosage would be hypotension and tachycardia; bradycardia could be encountered if parasympathetic (vagal) stimulation occurs. If symptomatic hypotension should occur, supportive treatment should be initiated. The dialyzability of olmesartan is unknown.
No lethality was observed in acute toxicity studies in mice and rats given single oral doses up to 2000 mg/kg olmesartan medoxomil. The minimum lethal oral dose of olmesartan medoxomil in dogs was greater than 1500 mg/kg.
Hydrochlorothiazide
The most common signs and symptoms of hydrochlorothiazide overdose observed in humans 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 degree to which hydrochlorothiazide is removed by hemodialysis has not been established. The oral LD₅₀ of hydrochlorothiazide is greater than 10 g/kg in both mice and rats.

11 DESCRIPTION

Olmesartan medoxomil and hydrochlorothiazide tablets are a combination of an angiotensin II receptor antagonist (AT₁ subtype), olmesartan medoxomil, and a thiazide diuretic, hydrochlorothiazide (HCTZ).

Olmesartan medoxomil is 2,3-dihydroxy-2-butenyl 4-(1-hydroxy-1-methylethyl)-2-propyl-1-[p — (o -1H -tetrazol-5­-ylphenyl)benzyl]imidazole-5-carboxylate, cyclic 2,3-carbonate.

Its molecular formula is C₂₉ H₃₀ N₆ O₆ and its structural formula is:

Olmesartan medoxomil USP is a white to off-white, crystalline powder with a molecular weight of 558.6. It is practically insoluble in water and sparingly soluble in methanol.

Hydrochlorothiazide is 6-chloro-3,4-dihydro-2H -1,2,4-benzo-thiadiazine-7-sulfonamide 1,1-dioxide. Its molecular formula is C₇ H₈ ClN₃ O₄ S₂ and its structural formula is:

Hydrochlorothiazide USP is a white or practically white, practically odorless, crystalline powder with a molecular weight of 297.7. Hydrochlorothiazide is slightly soluble in water but freely soluble in sodium hydroxide solution.

Olmesartan medoxomil and hydrochlorothiazide tablets are available for oral administration in tablets containing 20 mg or 40 mg of olmesartan medoxomil combined with 12.5 mg of hydrochlorothiazide, or 40 mg of olmesartan medoxomil combined with 25 mg of hydrochlorothiazide. Inactive ingredients include: hydroxypropyl cellulose, hypromellose, iron oxide red, iron oxide yellow, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, talc, and titanium dioxide.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Olmesartan medoxomil
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. Olmesartan blocks the vasoconstrictor effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT₁ receptor in vascular smooth muscle. Its action is, therefore, independent of the pathways for angiotensin II synthesis.
An AT₂ receptor is found also in many tissues, but this receptor is not known to be associated with cardiovascular homeostasis. Olmesartan has more than a 12,500-fold greater affinity for the AT₁ receptor than for the AT₂ receptor.
Blockade of the angiotensin II receptor inhibits the negative regulatory feedback of angiotensin II on renin secretion, but the resulting increased plasma renin activity and circulating angiotensin II levels do not overcome the effect of olmesartan on blood pressure.
Hydrochlorothiazide
Hydrochlorothiazide is a thiazide diuretic. Thiazides affect the renal tubular mechanisms of electrolyte reabsorption, directly increasing excretion of sodium and chloride in approximately equivalent amounts. Indirectly, the diuretic action of hydrochlorothiazide reduces plasma volume, with consequent increases in plasma renin activity, increases in aldosterone secretion, increases in urinary potassium loss, and decreases in serum potassium. The renin-aldosterone link is mediated by angiotensin II, so co-administration of an angiotensin II receptor antagonist tends to reverse the potassium loss associated with these diuretics. The mechanism of the antihypertensive effect of thiazides is not fully understood.

12.2 Pharmacodynamics

Olmesartan medoxomil
Olmesartan medoxomil doses of 2.5 to 40 mg inhibit the pressor effects of angiotensin I infusion. The duration of the inhibitory effect was related to dose, with doses of olmesartan medoxomil >40 mg giving >90% inhibition at 24 hours.
Plasma concentrations of angiotensin I and angiotensin II and plasma renin activity (PRA) increase after single and repeated administration of olmesartan medoxomil to healthy subjects and hypertensive patients. Repeated administration of up to 80 mg olmesartan medoxomil had minimal influence on aldosterone levels and no effect on serum potassium.
Hydrochlorothiazide
After oral administration of hydrochlorothiazide, diuresis begins within 2 hours, peaks in about 4 hours and lasts about 6 to 12 hours.
Drug Interactions
Hydrochlorothiazide
Alcohol, barbiturates, or narcotics: Potentiation of orthostatic hypotension may occur.
Skeletal muscle relaxants, non-depolarizing (e.g., tubocurarine): Increased responsiveness to the muscle relaxant may occur.
Digitalis glycosides: Thiazide-induced hypokalemia or hypomagnesemia may predispose to digoxin toxicity.

12.3 Pharmacokinetics

Absorption
Olmesartan: Olmesartan medoxomil is completely bioactivated by ester hydrolysis to olmesartan during absorption from the gastrointestinal tract. The absolute bioavailability of olmesartan is approximately 26%. After oral administration, the peak plasma concentration (C_max ) of olmesartan is reached after 1 to 2 hours. Food does not affect the bioavailability of olmesartan.
Olmesartan shows linear pharmacokinetics following single oral doses of up to 320 mg and multiple oral doses of up to 80 mg. Steady-state levels of olmesartan are achieved within 3 to 5 days and no accumulation in plasma occurs with once-daily dosing.
Hydrochlorothiazide: The estimated absolute bioavailability of hydrochlorothiazide after oral administration is about 70%. Peak plasma hydrochlorothiazide concentrations (C_max ) are reached within 2 to 5 hours after oral administration. There is no clinically significant effect of food on the bioavailability of hydrochlorothiazide.
The pharmacokinetics of hydrochlorothiazide is dose proportional in the range of 12.5 to 75 mg.
Distribution
Olmesartan: The volume of distribution of olmesartan is approximately 17 L. Olmesartan is highly bound to plasma proteins (99%) and does not penetrate red blood cells. The protein binding is constant at plasma olmesartan concentrations well above the range achieved with recommended doses.
In rats, olmesartan crossed the blood-brain barrier poorly, if at all. Olmesartan passed across the placental barrier in rats and was distributed to the fetus. Olmesartan was distributed to milk at low levels in rats.
Hydrochlorothiazide: Hydrochlorothiazide binds to albumin (40 to 70%) and distributes into erythrocytes. Following oral administration, plasma hydrochlorothiazide concentrations decline bi-exponentially, with a mean distribution half-life of about 2 hours and an elimination half-life of about 10 hours.
Hydrochlorothiazide crosses the placental but not the blood-brain barrier and is excreted in breast milk.
Metabolism
Olmesartan: Olmesartan does not undergo further metabolism.
Hydrochlorothiazide: Hydrochlorothiazide is not metabolized.
Elimination
Olmesartan: Olmesartan appears to be eliminated in a biphasic manner with a terminal elimination half-life of approximately 13 hours. Total plasma clearance of olmesartan is 1.3 L/h, with a renal clearance of 0.6 L/h. Approximately 35% to 50% of the absorbed dose is recovered in urine while the remainder is eliminated in feces via the bile.
Hydrochlorothiazide: About 70% of an orally administered dose of hydrochlorothiazide is eliminated in the urine as unchanged drug.
Specific populations
Olmesartan medoxomil
Pediatric: The pharmacokinetics of olmesartan were studied in pediatric hypertensive patients aged 1 to16 years. The clearance of olmesartan in pediatric patients was similar to that in adult patients when adjusted by the body weight. Olmesartan pharmacokinetics have not been investigated in pediatric patients less than 1 year of age.
Geriatric: The pharmacokinetics of olmesartan were studied in the elderly (≥65 years). Overall, maximum plasma concentrations of olmesartan were similar in young adults and the elderly. Modest accumulation of olmesartan was observed in the elderly with repeated dosing; AUC_ss , τ was 33% higher in elderly patients, corresponding to an approximate 30% reduction in CL_R .
Gender: Minor differences were observed in the pharmacokinetics of olmesartan in women compared to men. AUC and C_max were 10 to 15% higher in women than in men.
Renal insufficiency: In patients with renal insufficiency, serum concentrations of olmesartan were elevated compared to subjects with normal renal function. After repeated dosing, the AUC was approximately tripled in patients with severe renal impairment (creatinine clearance <20 mL/min). The pharmacokinetics of olmesartan in patients undergoing hemodialysis has not been studied.
Hepatic insufficiency: Increases in AUC_0-∞ and C_max for olmesartan were observed in patients with moderate hepatic impairment compared to those in matched controls, with an increase in AUC of about 60%.
Hydrochlorothiazide
Renal insufficiency: In a study in individuals with impaired renal function, the mean elimination half-life of hydrochlorothiazide doubled in individuals with mild/moderate renal impairment (30 < CrCl < 90 mL/min) and tripled in severe renal impairment (≤30 mL/min), when compared to individuals with normal renal function (CrCl > 90 mL/min).
Drug Interactions
Olmesartan
No significant drug interactions were reported in studies in which olmesartan medoxomil was co-administered with digoxin or warfarin in healthy volunteers.
The bioavailability of olmesartan medoxomil was not significantly altered by the co-administration of antacids [Al(OH)₃ /Mg(OH)₂ ].
Olmesartan medoxomil is not metabolized by the cytochrome P450 system and has no effects on P450 enzymes; thus, interactions with drugs that inhibit, induce, or are metabolized by those enzymes are not expected.
Bile acid sequestering agent colesevelam
Concomitant administration of 40 mg olmesartan medoxomil and 3750 mg colesevelam hydrochloride in healthy subjects resulted in 28% reduction in C_max and 39% reduction in AUC of olmesartan. Lesser effects, 4% and 15% reduction in C_max and AUC respectively, were observed when olmesartan medoxomil was administered 4 hours prior to colesevelam hydrochloride [see Drug Interactions (7.5)].

Hydrochlorothiazide
Drugs that alter gastrointestinal motility: The bioavailability of thiazide-type diuretics may be increased by anticholinergic agents (e.g. atropine, biperiden), apparently due to a decrease in gastrointestinal motility and the stomach emptying rate. Conversely, pro-kinetic drugs may decrease the bioavailability of thiazide diuretics.
Cholestyramine: In a dedicated drug interaction study, administration of cholestyramine 2 h before hydrochlorothiazide resulted in a 70% reduction in exposure to hydrochlorothiazide. Further, administration of hydrochlorothiazide 2 h before cholestyramine, resulted in 35% reduction in exposure to hydrochlorothiazide.
Lithium: Diuretic agents reduce the renal clearance of lithium and increase the risk of lithium toxicity [see Drug Interactions (7.2)].
Antineoplastic agents (e.g. cyclophosphamide, methotrexate): Concomitant use of thiazide diuretics may reduce renal excretion of cytotoxic agents and enhance their myelosuppressive effects.