Telmisartan and Hydrochlorothiazide

INDICATIONS AND USAGE Telmisartan and hydrochlorothiazide tablets are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes including the classes to which this drug principally belongs. There are no controlled trials demonstrating risk reduction with telmisartan and hydrochlorothiazide tablets. Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals. For specific advice on goals and management, see published guidelines, such as those of the National High Blood Pressure Education Program’s Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC). Numerous antihypertensive drugs, from a variety of pharmacologic classes and with different mechanisms of action, have been shown in randomized controlled trials to reduce cardiovascular morbidity and mortality, and it can be concluded that it is blood pressure reduction, and not some other pharmacologic property of the drugs, that is largely responsible for those benefits. The largest and most consistent cardiovascular outcome benefit has been a reduction in the risk of stroke, but reductions in myocardial infarction and cardiovascular mortality also have been seen regularly. Elevated systolic or diastolic pressure causes increased cardiovascular risk, and the absolute risk increase per mmHg is greater at higher blood pressures, so that even modest reductions of severe hypertension can provide substantial benefit. Relative risk reduction from blood pressure reduction is similar across populations with varying absolute risk, so the absolute benefit is greater in patients who are at higher risk independent of their hypertension (for example, patients with diabetes or hyperlipidemia), and such patients would be expected to benefit from more aggressive treatment to a lower blood pressure goal. Some antihypertensive drugs have smaller blood pressure effects (as monotherapy) in black patients, and many antihypertensive drugs have additional approved indications and effects (e.g., on angina, heart failure, or diabetic kidney disease). These considerations may guide selection of therapy [see Clinical Studies ( 14 )]. Telmisartan and hydrochlorothiazide tablets are not indicated for initial therapy for the treatment of hypertension [see Dosage and Administration ( 2.1 )]. Telmisartan and hydrochlorothiazide tablets may be used alone or in combination with other antihypertensive agents. • Telmisartan and hydrochlorothiazide tablets are a combination of an angiotensin II receptor blocker (ARB) and a thiazide diuretic indicated for the treatment of hypertension, alone or with other antihypertensive agents, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions ( 1 ) • Telmisartan and hydrochlorothiazide tablets are not indicated for initial therapy ( 1 )

DOSAGE AND ADMINISTRATION The usual starting dose of telmisartan is 40 mg once a day; blood pressure response is dose related over the range of 20 to 80 mg. Patients with depletion of intravascular volume should have the condition corrected or telmisartan tablets should be initiated under close medical supervision (see WARNINGS, Hypotension in Volume Depleted Patients ). Patients with biliary obstructive disorders or hepatic insufficiency should have treatment started under close medical supervision (see PRECAUTIONS ). Hydrochlorothiazide is effective in doses of 12.5 mg to 50 mg once daily. To minimize dose-independent side effects, it is usually appropriate to begin combination therapy only after a patient has failed to achieve the desired effect with monotherapy. The side effects (see WARNINGS ) of telmisartan are generally rare and apparently independent of dose; those of hydrochlorothiazide are a mixture of dose-dependent phenomena (primarily hypokalemia) and dose-independent phenomena (e.g., pancreatitis), the former much more common than the latter. Therapy with any combination of telmisartan and hydrochlorothiazide will be associated with both sets of dose-independent side effects. Telmisartan and hydrochlorothiazide tablets may be administered with other antihypertensive agents. Telmisartan and hydrochlorothiazide tablets may be administered with or without food. Replacement Therapy The combination may be substituted for the titrated components. Dose Titration by Clinical Effect Telmisartan and hydrochlorothiazide tablets are available as tablets containing either telmisartan 40 mg and hydrochlorothiazide 12.5 mg, or telmisartan 80 mg and hydrochlorothiazide 12.5 mg or 25 mg. A patient whose blood pressure is not adequately controlled with telmisartan monotherapy 80 mg (see above) may be switched to telmisartan and hydrochlorothiazide tablets, telmisartan 80 mg/hydrochlorothiazide 12.5 mg once daily, and finally titrated up to 160/25 mg, if necessary. A patient whose blood pressure is inadequately controlled by 25 mg once daily of hydrochlorothiazide may be switched to telmisartan 80 mg/hydrochlorothiazide 12.5 mg or telmisartan 80 mg/hydrochlorothiazide 25 mg tablets once daily. The clinical response to telmisartan and hydrochlorothiazide tablets should be subsequently evaluated and if blood pressure remains uncontrolled after 2 to 4 weeks of therapy, the dose may be titrated up to 160/25 mg, if necessary. Those patients controlled by 25 mg hydrochlorothiazide but who experience hypokalemia with this regimen, may be switched to telmisartan 80 mg/hydrochlorothiazide 12.5 mg tablets once daily, reducing the dose of hydrochlorothiazide without reducing the overall expected antihypertensive response. Patients with Renal Impairment The usual regimens of therapy with telmisartan and hydrochlorothiazide tablets may be followed as long as the patient’s creatinine clearance is >30 mL/min. In patients with more severe renal impairment, loop diuretics are preferred to thiazides, so telmisartan and hydrochlorothiazide tablets are not recommended. Patients with Hepatic Impairment Telmisartan and hydrochlorothiazide tablets are not recommended for patients with severe hepatic impairment. Patients with biliary obstructive disorders or hepatic insufficiency should have treatment started under close medical supervision using the 40/12.5 mg combination (see PRECAUTIONS ).

WARNINGS Fetal Toxicity 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 telmisartan 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 intra-amniotic environment. If oligohydramnios is observed, discontinue telmisartan 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 telmisartan and hydrochlorothiazide for hypotension, oliguria, and hyperkalemia (see PRECAUTIONS , Pediatric Use ). No teratogenic effects were observed when telmisartan was administered to pregnant rats at oral doses of up to 50 mg/kg/day and to pregnant rabbits at oral doses up to 45 mg/kg/day. In rabbits, embryolethality associated with maternal toxicity (reduced body weight gain and food consumption) was observed at 45 mg/kg/day [about 12 times the maximum recommended human dose (MRHD) of 80 mg on a mg/m 2 basis]. In rats, maternally toxic (reduction in body weight gain and food consumption) telmisartan doses of 15 mg/kg/day (about 1.9 times the MRHD on a mg/m 2 basis), administered during late gestation and lactation, were observed to produce adverse effects in neonates, including reduced viability, low birth weight, delayed maturation, decreased weight gain. Telmisartan has been shown to be present in rat fetuses during late gestation and in rat milk. The no observed effect doses for developmental toxicity in rats and rabbits, 5 and 15 mg/kg/day, respectively, are about 0.64 and 3.7 times, on a mg/m 2 basis, the maximum recommended human dose of telmisartan (80 mg/day). Studies in which hydrochlorothiazide was administered to pregnant mice and rats during their periods of major organogenesis at doses up to 3000 and 1000 mg/kg/day, respectively, provided no evidence of harm to the fetus. Thiazides cross the placental barrier and appear in cord blood. There is a risk of fetal or neonatal jaundice, thrombocytopenia, and possibly other adverse reactions that have occurred in adults. Hypotension in Volume-Depleted Patients Initiation of antihypertensive therapy in patients whose renin-angiotensin system are activated such as patients who are intravascular volume- or sodium-depleted, e.g., in patients treated vigorously with diuretics, should only be approached cautiously. These conditions should be corrected prior to administration of telmisartan and hydrochlorothiazide tablets. Treatment should be started under close medical supervision (see DOSAGE AND ADMINISTRATION ). If hypotension occurs, the patients should be placed in the supine position and, if necessary, given an intravenous infusion of normal saline. A transient hypotensive response is not a contraindication to further treatment which usually can be continued without difficulty once the blood pressure has stabilized. Hydrochlorothiazide Hepatic Impairment : Thiazide diuretics should be used with caution in patients with impaired hepatic function or progressive liver disease, since minor alterations of fluid and electrolyte balance may precipitate hepatic coma. Hypersensitivity Reaction : Hypersensitivity reactions to hydrochlorothiazide may occur in patients with or without a history of allergy or bronchial asthma, but are more likely in patients with such a history. Systemic Lupus Erythematosus : Thiazide diuretics have been reported to cause exacerbation or activation of systemic lupus erythematosus. Lithium Interaction : Lithium generally should not be given with thiazides (see PRECAUTIONS, Drug Interactions, Hydrochlorothiazide , Lithium ). Acute Myopia and Secondary Angle-Closure Glaucoma: Hydrochlorothiazide, a sulfonamide, can cause an idiosyncratic reaction, resulting in acute transient myopia and acute angle-closure glaucoma. Symptoms include acute onset of decreased visual acuity or ocular pain and typically occur within hours to weeks of drug initiation. Untreated angle-closure glaucoma can lead to permanent vision loss. The primary treatment is to discontinue hydrochlorothiazide as rapidly as possible. Prompt medical or surgical treatments may need to be considered if the intraocular pressure remains uncontrolled. Risk factors for developing acute angle-closure glaucoma may include a history of sulfonamide or penicillin allergy.

CONTRAINDICATIONS Telmisartan and hydrochlorothiazide tablets, USP are contraindicated in patients with known hypersensitivity (e.g., anaphylaxis or angioedema) to telmisartan, hydrochlorothiazide, or any other component of this product (see ADVERSE REACTIONS ). Because of the hydrochlorothiazide component, this product is contraindicated in patients with anuria or hypersensitivity to other sulfonamide-derived drugs. Do not co-administer aliskiren with telmisartan and hydrochlorothiazide tablets in patients with diabetes (see PRECAUTIONS , Drug Interactions ).

Drug Interactions Telmisartan Aliskiren: Do not co-administer aliskiren with telmisartan and hydrochlorothiazide tablets in patients with diabetes. Avoid use of aliskiren with telmisartan and hydrochlorothiazide tablets in patients with renal impairment (GFR <60 mL/min). Digoxin : When telmisartan was co-administered with digoxin, median increases in digoxin peak plasma concentration (49%) and in trough concentration (20%) were observed. It is, therefore, recommended that digoxin levels be monitored when initiating, adjusting, and discontinuing telmisartan to avoid possible over- or under-digitalization. Lithium: Reversible increases in serum lithium concentrations and toxicity have been reported during concomitant administration of lithium with angiotensin converting enzyme inhibitors. Cases have also been reported with angiotensin II receptor antagonists including telmisartan. Because lithium should not be used with diuretics, the use of lithium with telmisartan and hydrochlorothiazide is not recommended. Non-Steroidal Anti-Inflammatory Agents including Selective Cyclooxygenase-2 Inhibitors (COX-2 Inhibitors) : 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 telmisartan, may result in deterioration of renal function, including possible acute renal failure. These effects are usually reversible. Monitor renal function periodically in patients receiving telmisartan and NSAID therapy. The antihypertensive effect of angiotensin II receptor antagonists, including telmisartan may be attenuated by NSAIDs including selective COX-2 inhibitors. Ramipril and Ramiprilat: Co-administration of telmisartan 80 mg once daily and ramipril 10 mg once daily to healthy subjects increases steady-state C max and AUC of ramipril 2.3 and 2.1 fold, respectively, and C max and AUC of ramiprilat 2.4 and 1.5 fold, respectively. In contrast, C max and AUC of telmisartan decrease by 31% and 16%, respectively. When co-administering telmisartan and ramipril, the response may be greater because of the possibly additive pharmacodynamic effects of the combined drugs, and also because of the increased exposure to ramipril and ramiprilat in the presence of telmisartan. Warfarin : Telmisartan administered for 10 days slightly decreased the mean warfarin trough plasma concentration; this decrease did not result in a change in International Normalized Ratio (INR). Other Drugs : Co-administration of telmisartan did not result in a clinically significant interaction with acetaminophen, amlodipine, glibenclamide, simvastatin, hydrochlorothiazide or ibuprofen. Telmisartan is not metabolized by the cytochrome P450 system and had no effects in vitro on cytochrome P450 enzymes, except for some inhibition of CYP2C19. Telmisartan is not expected to interact with drugs that inhibit cytochrome P450 enzymes; it is also not expected to interact with drugs metabolized by cytochrome P450 enzymes, except for possible inhibition of the metabolism of drugs metabolized by CYP2C19. Hydrochlorothiazide When administered concurrently, the following drugs may interact with thiazide diuretics: Alcohol, barbiturates, or narcotics : Potentiation of orthostatic hypotension may occur. Antidiabetic drugs (oral agents and insulin) : Dosage adjustment of the antidiabetic drug may be required. Other antihypertensive drugs : Additive effect or potentiation. Cholestyramine and colestipol resins : Absorption of hydrochlorothiazide is impaired in the presence of anionic exchange resins. Single doses of either cholestyramine or colestipol resins bind the hydrochlorothiazide and reduce its absorption from the gastrointestinal tract by up to 85% and 43%, respectively. Corticosteroids, ACTH : Intensified electrolyte depletion, particularly hypokalemia. Pressor amines (e.g., norepinephrine) : Possible decreased response to pressor amines but not sufficient to preclude their use. Skeletal muscle relaxants, nondepolarizing (e.g., tubocurarine) : Possible increased responsiveness to the muscle relaxant. Lithium : Should not generally be given with diuretics. Diuretic agents reduce the renal clearance of lithium and add a high risk of lithium toxicity. Refer to the package insert for lithium preparations before use of such preparations with telmisartan and hydrochlorothiazide tablets. Non-steroidal anti-inflammatory drugs : In some patients, the administration of a non-steroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. Therefore, when telmisartan and hydrochlorothiazide tablets and non-steroidal anti-inflammatory agents are used concomitantly, the patient should be observed closely to determine if the desired effect of the diuretic is obtained.

ADVERSE REACTIONS Telmisartan and hydrochlorothiazide tablets has been evaluated for safety in over 1700 patients, including 716 treated for over six months and 420 for over one year. In clinical trials with telmisartan and hydrochlorothiazide tablets, no unexpected adverse events have been observed. Adverse experiences have been limited to those that have been previously reported with telmisartan and/or hydrochlorothiazide. The overall incidence of adverse experiences reported with the combination was comparable to placebo. Most adverse experiences were mild in intensity and transient in nature and did not require discontinuation of therapy. Adverse events occurring at an incidence of 2% or more in patients treated with telmisartan/hydrochlorothiazide and at a greater rate than in patients treated with placebo, irrespective of their causal association, are presented in Table 1. TABLE 1 Adverse Events Occurring ≥2% of Telmisartan/Hydrochlorothiazide (HCTZ) Patients* Telm/HCTZ (N=414) (%) Placebo (N=74) (%) Telm (N=209) (%) HCTZ (N=121) (%) Body as a whole Fatigue 3 1 3 3 Influenza-like symptoms 2 1 2 3 Central/peripheral nervous system Dizziness 5 1 4 6 Gastrointestinal system Diarrhea 3 0 5 2 Nausea 2 0 1 2 Respiratory system disorder Sinusitis 4 3 3 6 Upper respiratory tract infection 8 7 7 10 * includes all doses of telmisartan (20 to 160 mg), hydrochlorothiazide (6.25 to 25 mg), and combinations thereof The following adverse events were reported at a rate less than 2% in patients treated with telmisartan/hydrochlorothiazide and at a greater rate than in patients treated with placebo: back pain, dyspepsia, vomiting, tachycardia, hypokalemia, bronchitis, pharyngitis, rash, hypotension postural, abdominal pain. Finally, the following adverse events were reported at a rate of 2% or greater in patients treated with telmisartan/hydrochlorothiazide, but were as, or more common in the placebo group: pain, headache, cough, urinary tract infection. Adverse events occurred at approximately the same rates in men and women, older and younger patients, and black and non-black patients. In controlled trials (n=1017), 0.3% of patients treated with telmisartan and hydrochlorothiazide tablets 40/12.5 mg, 80/12.5 mg or 80/25 mg discontinued due to orthostatic hypotension, and the incidence of dizziness was 4%, 7%, and 1% respectively. Telmisartan Other adverse experiences that have been reported with telmisartan, without regard to causality, are listed below: Autonomic Nervous System : impotence, increased sweating, flushing Body as a Whole : allergy, fever, leg pain, malaise, chest pain Cardiovascular : palpitation, dependent edema, angina pectoris, leg edema, abnormal ECG, hypertension, peripheral edema CNS : insomnia, somnolence, migraine, vertigo, paresthesia, involuntary muscle contractions, hypoaesthesia Gastrointestinal : flatulence, constipation, gastritis, dry mouth, hemorrhoids, gastroenteritis, enteritis, gastroesophageal reflux, toothache, non-specific gastrointestinal disorders Metabolic : gout, hypercholesterolemia, diabetes mellitus Musculoskeletal : arthritis, arthralgia, leg cramps, myalgia Psychiatric : anxiety, depression, nervousness Resistance Mechanism : infection, fungal infection, abscess, otitis media Respiratory : asthma, rhinitis, dyspnea, epistaxis Skin : dermatitis, eczema, pruritus Urinary : micturition frequency, cystitis Vascular : cerebrovascular disorder Special Senses : abnormal vision, conjunctivitis, tinnitus, earache A single case of angioedema was reported (among a total of 3781 patients treated with telmisartan). Hydrochlorothiazide Other adverse experiences that have been reported with hydrochlorothiazide, without regard to causality, are listed below: Body as a whole : weakness Digestive : pancreatitis, jaundice (intrahepatic cholestatic jaundice), sialadenitis, cramping, gastric irritation Hematologic : aplastic anemia, agranulocytosis, leukopenia, hemolytic anemia, thrombocytopenia Hypersensitivity : purpura, photosensitivity, urticaria, necrotizing angiitis (vasculitis and cutaneous vasculitis), fever, respiratory distress including pneumonitis and pulmonary edema, anaphylactic reactions Metabolic : hyperglycemia, glycosuria, hyperuricemia Musculoskeletal : muscle spasm Nervous System/Psychiatric : restlessness Renal : renal failure, renal dysfunction, interstitial nephritis Skin : erythema multiforme including Stevens-Johnson syndrome, exfoliative dermatitis including toxic epidermal necrolysis Special Senses : transient blurred vision, xanthopsia Post-Marketing Experience The following adverse reactions have been identified during post-approval use of telmisartan tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to estimate reliably their frequency or establish a causal relationship to drug exposure. Decisions to include these reactions in labeling are typically based on one or more of the following factors: (1) seriousness of the reaction, (2) frequency of reporting, or (3) strength of causal connection to telmisartan tablets. The most frequently spontaneously reported events include: headache, dizziness, asthenia, coughing, nausea, fatigue, weakness, edema, face edema, lower limb edema, angioneurotic edema, urticaria, hypersensitivity, sweating increased, erythema, chest pain, atrial fibrillation, congestive heart failure, myocardial infarction, blood pressure increased, hypertension aggravated, hypotension (including postural hypotension), hyperkalemia, syncope, dyspepsia, diarrhea, pain, urinary tract infection, erectile dysfunction, back pain, abdominal pain, muscle cramps (including leg cramps), myalgia, bradycardia, eosinophilia, thrombocytopenia, uric acid increased, abnormal hepatic function/liver disorder, renal impairment including acute renal failure, anemia, increased CPK, anaphylactic reaction, and tendon pain (including tendonitis, tenosynovitis), drug eruption (toxic skin eruption mostly reported as toxicoderma, rash, and urticaria), hypoglycemia (in diabetic patients), and angioedema (with fatal outcome). Rare cases of rhabdomyolysis have been reported in patients receiving angiotensin II receptor blockers, including telmisartan tablets. Clinical Laboratory Findings In controlled trials, clinically relevant changes in standard laboratory test parameters were rarely associated with administration of telmisartan and hydrochlorothiazide tablets. Hemoglobin and Hematocrit : Decreases in hemoglobin (≥2 g/dL) and hematocrit (≥9%) were observed in 1.2% and 0.6% of telmisartan/hydrochlorothiazide patients, respectively, in controlled trials. Changes in hemoglobin and hematocrit were not considered clinically significant and there were no discontinuations due to anemia. Creatinine, Blood Urea Nitrogen (BUN) : Increases in BUN (≥11.2 mg/dL) and serum creatinine (≥0.5 mg/dL) were observed in 2.8% and 1.4%, respectively, of patients with essential hypertension treated with telmisartan and hydrochlorothiazide tablets in controlled trials. No patient discontinued treatment with telmisartan and hydrochlorothiazide tablets due to an increase in BUN or creatinine. Liver Function Tests : Occasional elevations of liver enzymes and/or serum bilirubin have occurred. No telmisartan/ hydrochlorothiazide treated patients discontinued therapy due to abnormal hepatic function. Serum Electrolytes : See PRECAUTIONS .

CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Telmisartan and Hydrochlorothiazide Telmisartan and hydrochlorothiazide is a combination of two drugs with antihypertensive properties: a thiazide diuretic, hydrochlorothiazide, and an angiotensin II receptor blocker (ARB), telmisartan. Telmisartan 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 blocks the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT 1 receptor in many tissues, such as vascular smooth muscle and the adrenal gland. Its action is therefore independent of the pathways for angiotensin II synthesis. There is also an AT 2 receptor found in many tissues, but AT 2 is not known to be associated with cardiovascular homeostasis. Telmisartan has much greater affinity (>3,000-fold) for the AT 1 receptor than for the AT 2 receptor. Telmisartan does not inhibit ACE (kininase II) nor does it bind to or block other hormone receptors or ion channels known to be important in cardiovascular regulation. 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 angiotensin II circulating levels do not overcome the effect of telmisartan on blood pressure. Hydrochlorothiazide Hydrochlorothiazide is a thiazide diuretic. Thiazides affect the renal tubular mechanisms of electrolyte reabsorption, directly increasing excretion of sodium salt 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 ARB 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 Telmisartan In normal volunteers, a dose of telmisartan 80 mg inhibited the pressor response to an intravenous infusion of angiotensin II by approximately 90% at peak plasma concentrations with approximately 40% inhibition persisting for 24 hours. Plasma concentration of angiotensin II and plasma renin activity increased in a dose-dependent manner after single administration of telmisartan to healthy subjects and repeated administration to hypertensive patients. The once-daily administration of up to 80 mg telmisartan to healthy subjects did not influence plasma aldosterone concentrations. In multiple dose studies with hypertensive patients, there were no clinically significant changes in electrolytes (serum potassium or sodium) or in metabolic function (including serum levels of cholesterol, triglycerides, HDL, LDL, glucose, or uric acid). The antihypertensive effects of telmisartan have been studied in six placebo-controlled clinical trials including a total of 1773 patients with mild to moderate hypertension (diastolic blood pressure of 95 to 114 mmHg), 1031 of whom were treated with telmisartan. Following once-daily administration of telmisartan, the magnitude of blood pressure reduction from baseline after placebo subtraction was approximately (SBP/DBP) 6-8/6 mmHg for 20 mg, 9-13/6-8 mmHg for 40 mg, and 12-13/7-8 mmHg for 80 mg. Larger doses (up to 160 mg) did not appear to cause a further decrease in blood pressure. The onset of antihypertensive activity occurs within 3 hours, with a maximal reduction by approximately 4 weeks. At doses of 20, 40, and 80 mg, the antihypertensive effect of once-daily administration of telmisartan was maintained for the full 24-hour dose interval. In 30 hypertensive patients with normal renal function treated for 8 weeks with telmisartan 80 mg or telmisartan 80 mg in combination with hydrochlorothiazide 12.5 mg, there were no clinically significant changes from baseline in renal blood flow, glomerular filtration rate, filtration fraction, renovascular resistance, or creatinine clearance. Hydrochlorothiazide After oral administration of hydrochlorothiazide, diuresis begins within 2 hours, peaks in about 4 hours, and lasts approximately 6 to 12 hours. Drug Interactions Hydrochlorothiazide Alcohol, barbiturates, or narcotics: Potentiation of orthostatic hypotension may occur. Skeletal muscle relaxants : Possible increased responsiveness to muscle relaxants such as curare derivatives. Corticosteroids, ACTH: Intensified electrolyte depletion, particularly hypokalemia. Pressor amines (e.g., norepinephrine): Possible decreased response to pressor amines but not sufficient to preclude their use. 12.3 Pharmacokinetics Telmisartan Absorption: Following oral administration, peak concentrations (C max ) of telmisartan are reached in 0.5 to 1 hour after dosing. Food slightly reduces the bioavailability of telmisartan, with a reduction in the area under the plasma concentration-time curve (AUC) of approximately 6% with 40 mg and approximately 20% after a 160 mg dose. Telmisartan and hydrochlorothiazide can be administered with or without food. The absolute bioavailability of telmisartan is dose dependent. At 40 mg and 160 mg, the bioavailability was 42% and 58%, respectively. The pharmacokinetics of telmisartan with orally administered telmisartan are nonlinear over the dose range 20 mg to 160 mg, with greater than proportional increases of plasma concentrations (C max and AUC) with increasing doses. Telmisartan shows bi-exponential decay kinetics with a terminal elimination half-life of approximately 24 hours. Trough plasma concentrations of telmisartan with once-daily dosing are approximately 10% to 25% of peak plasma concentrations. Telmisartan has an accumulation index in plasma of 1.5 to 2.0 upon repeated once-daily dosing. Distribution: Telmisartan is highly bound to plasma proteins (>99.5%), mainly albumin and α 1 -acid glycoprotein. Plasma protein binding is constant over the concentration range achieved with recommended doses. The volume of distribution for telmisartan is approximately 500 liters, indicating additional tissue binding. Metabolism: Telmisartan is metabolized by conjugation to form a pharmacologically inactive acyl glucuronide; the glucuronide of the parent compound is the only metabolite that has been identified in human plasma and urine. After a single dose, the glucuronide represents approximately 11% of the measured radioactivity in plasma. The cytochrome P450 isoenzymes are not involved in the metabolism of telmisartan. Elimination: Following either intravenous or oral administration of 14 C-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). Total plasma clearance of telmisartan is >800 mL/min. Terminal half-life and total clearance appear to be independent of dose. Hydrochlorothiazide Hydrochlorothiazide is not metabolized but is eliminated rapidly by the kidney. When plasma levels have been followed for at least 24 hours, the plasma half-life has been observed to vary between 5.6 and 14.8 hours. At least 61% of the oral dose is eliminated unchanged within 24 hours. Hydrochlorothiazide crosses the placental but not the blood-brain barrier and is excreted in breast milk. Specific Populations Telmisartan Renal Insufficiency: Telmisartan is not removed from blood by hemofiltration and is not dialyzable [see Warnings and Precautions (5.3) and Use in Specific Populations (8.7)]. Hepatic Insufficiency : In patients with he