Sequence 1
CLINICAL PHARMACOLOGY Mechanism of Action and Pharmacodynamics Pravachol Cholesterol and triglycerides in the bloodstream circulate as part of lipoprotein complexes. These complexes can be separated by density ultracentrifugation into high (HDL), intermediate (IDL), low (LDL), and very low (VLDL) density lipoprotein fractions. Triglycerides (TG) and cholesterol synthesized in the liver are incorporated into very low density lipoproteins (VLDLs) and released into the plasma for delivery to peripheral tissues. In a series of subsequent steps, VLDLs are transformed into intermediate density lipoproteins (IDLs), and cholesterol-rich low density lipoproteins (LDLs). High density lipoproteins (HDLs), containing apolipoprotein A, are hypothesized to participate in the reverse transport of cholesterol from tissues back to the liver. PRAVACHOL produces its lipid-lowering effect in two ways. First, as a consequence of its reversible inhibition of HMG-CoA reductase activity, it effects modest reductions in intracellular pools of cholesterol. This results in an increase in the number of LDL-receptors on cell surfaces and enhanced receptor-mediated catabolism and clearance of circulating LDL. Second, pravastatin inhibits LDL production by inhibiting hepatic synthesis of VLDL, the LDL precursor. Clinical and pathologic studies have shown that elevated levels of total cholesterol (Total-C), low density lipoprotein cholesterol (LDL-C), and apolipoprotein B (Apo B - a membrane transport complex for LDL) promote human atherosclerosis. Similarly, decreased levels of HDL-cholesterol (HDL-C) and its transport complex, apolipoprotein A, are associated with the development of atherosclerosis. Epidemiologic investigations have established that cardiovascular morbidity and mortality vary directly with the level of Total-C and LDL-C and inversely with the level of HDL-C. Like LDL, cholesterol-enriched triglyceride-rich lipoproteins, including VLDL, IDL, and remnants, can also promote atherosclerosis. Elevated plasma TG are frequently found in a triad with low HDL-C levels and small LDL particles, as well as in association with non-lipid metabolic risk factors for coronary heart disease. As such, total plasma TG has not consistently been shown to be an independent risk factor for coronary heart disease (CHD). Furthermore, the independent effect of raising HDL or lowering TG on the risk of coronary and cardiovascular morbidity and mortality has not been determined. In both normal volunteers and patients with hypercholesterolemia, treatment with PRAVACHOL reduced Total-C, LDL-C, and apolipoprotein B. PRAVACHOL also reduced VLDL-C and TG and produced increases in HDL-C and apolipoprotein A. Buffered Aspirin Aspirin affects platelet aggregation by irreversibly inhibiting prostaglandin cyclo-oxygenase. This effect lasts for the life of the platelet and prevents the formation of the platelet aggregating factor thromboxane A 2 . Nonacetylated salicylates do not inhibit this enzyme and have no effect on platelet aggregation. At somewhat higher doses, aspirin reversibly inhibits the formation of prostaglandin I 2 (prostacyclin), which is an arterial vasodilator and inhibits platelet aggregation. Buffered Aspirin and Pravastatin Pharmacodynamic Interactions There is no evidence of a pharmacodynamic effect of aspirin on the lipid lowering effect of pravastatin (see Table 1 ). Table 1: Lipid Lowering Effect of Pravastatin With and Without Aspirin Mean Percent Change from Baseline * Total-C LDL-C HDL-C TG * On-treatment lipid measures at 3 months from randomization in CARE study. Pravastatin/Aspirin (N=1730) -22% -31% +5% -11% Pravastatin/Placebo (N=336) -21% -30% +6% -9% Placebo/Aspirin (N=1717) 0% -1% +1% +5% Placebo/Placebo (N=336) -1% -1% 0% +3% No study of the effect of pravastatin on the pharmacodynamics of aspirin has been performed. Pharmacokinetics/Metabolism Pravachol Absorption and Distribution PRAVACHOL (pravastatin sodium) is administered orally in the active form. In clinical pharmacology studies in man, pravastatin is rapidly absorbed, with peak plasma levels of parent compound attained 1 to 1.5 hours following ingestion. Based on urinary recovery of radiolabeled drug, the average oral absorption of pravastatin is 34% and absolute bioavailability is 17%. While the presence of food in the gastrointestinal tract reduces systemic bioavailability, the lipid-lowering effects of the drug are similar whether taken with, or 1 hour prior to, meals. Pravastatin undergoes extensive first-pass extraction in the liver (extraction ratio 0.66), which is its primary site of action, and the primary site of cholesterol synthesis and of LDL-C clearance. In vitro studies demonstrated that pravastatin is transported into hepatocytes with substantially less uptake into other cells. Pravastatin plasma concentrations [including: area under the concentration-time curve (AUC), peak (C max ), and steady-state minimum (C min )] are directly proportional to administered dose. Systemic bioavailability of pravastatin administered following a bedtime dose was decreased 60% compared to that following an AM dose. Despite this decrease in systemic bioavailability, the efficacy of pravastatin administered once daily in the evening, although not statistically significant, was marginally more effective than that after a morning dose. This finding of lower systemic bioavailability suggests greater hepatic extraction of the drug following the evening dose. Steady-state AUCs, C max and C min plasma concentrations showed no evidence of pravastatin accumulation following once or twice daily administration of PRAVACHOL tablets. Approximately 50% of the circulating drug is bound to plasma proteins. Pravastatin, like other HMG-CoA reductase inhibitors, has variable bioavailability. The coefficient of variation, based on between-subject variability, was 50% to 60% for AUC. Metabolism and Elimination Approximately 20% of a radiolabeled oral dose is excreted in urine and 70% in the feces. After intravenous administration of radiolabeled pravastatin to normal volunteers, approximately 47% of total body clearance was via renal excretion and 53% by non-renal routes (i.e., biliary excretion and biotransformation). Since there are dual routes of elimination, the potential exists both for compensatory excretion by the alternate route as well as for accumulation of drug and/or metabolites in patients with renal or hepatic insufficiency. In a study comparing the kinetics of pravastatin in patients with biopsy confirmed cirrhosis (N=7) and normal subjects (N=7), the mean AUC varied 18-fold in cirrhotic patients and 5-fold in healthy subjects. Similarly, the peak pravastatin values varied 47-fold for cirrhotic patients compared to 6-fold for healthy subjects. Biotransformation pathways elucidated for pravastatin include: (a) isomerization to 6-epi pravastatin and the 3α-hydroxyisomer of pravastatin (SQ 31,906), (b) enzymatic ring hydroxylation to SQ 31,945, (c) ω-1 oxidation of the ester side chain, (d) β-oxidation of the carboxy side chain, (e) ring oxidation followed by aromatization, (f) oxidation of a hydroxyl group to a keto group, and (g) conjugation. The major degradation product is the 3α-hydroxy isomeric metabolite, which has one-tenth to one-fortieth the HMG-CoA reductase inhibitory activity of the parent compound. Following single dose administration of 14 C-pravastatin, the elimination half-life (t ½ ) for total radioactivity (pravastatin plus metabolites) in humans is 77 hours. Special Populations Geriatric: In a single oral dose study using pravastatin 20 mg, the mean AUC for pravastatin was approximately 27% greater and the mean cumulative urinary excretion (CUE) approximately 19% lower in elderly men (65 to 75 years old) compared with younger men (19 to 31 years old). In a similar study conducted in women, the mean AUC for pravastatin was approximately 46% higher and the mean CUE approximately 18% lower in elderly women (65 to 78 years old) compared with younger women (18 to 38 years old). In both studies, C max , T max and t ½ values were similar in older and younger subjects. Buffered Aspirin Absorption In general, immediate-release aspirin is well and completely absorbed from the gastrointestinal (GI) tract. Following absorption, aspirin is hydrolyzed to salicylic acid with peak plasma levels of salicylic acid occurring within 1-2 hours of dosing (see Pharmacokinetics/Metabolism: Buffered Aspirin: Metabolism ). Distribution Salicylic acid is widely distributed to all tissues and fluids in the body including the central nervous system (CNS), breast milk, and fetal tissues. The highest concentrations are found in the plasma, liver, renal cortex, heart, and lungs. The protein binding of salicylate is concentration-dependent, i.e., nonlinear. At low concentrations (<100 micrograms per milliliter [µg/mL]), approximately 90% of plasma salicylate is bound to albumin while at higher concentrations (>400 µg/mL), only about 75% is bound. Metabolism Aspirin is rapidly hydrolyzed in the plasma to salicylic acid such that plasma levels of aspirin are essentially undetectable 1-2 hours after dosing. Salicylic acid is primarily conjugated in the liver to form salicyluric acid, a phenolic glucuronide, an acyl glucuronide, and a number of minor metabolites. Salicylic acid has a plasma half-life of approximately 6 hours. Salicylate metabolism is saturable and total body clearance decreases at higher serum concentrations due to the limited ability of the liver to form both salicyluric acid and phenolic glucuronide. Following toxic doses (10-20 grams [g]), the plasma half-life may be increased to over 20 hours. Elimination The elimination of salicylic acid follows zero order pharmacokinetics; (i.e., the rate of drug elimination is constant in relation to plasma concentration). Renal excretion of unchanged drug depends upon urine pH. As urinary pH rises above 6.5, the renal clearance of free salicylate increases from <5% to >80%. Alkalinization of the urine is a key concept in the management of salicylate overdose. (See OVERDOSAGE: Buffered Aspirin .) Following therapeutic doses, approximately 10% is found excreted in the urine as salicylic acid, 75% as salicyluric acid, and 10% phenolic and 5% acyl glucuronides of salicylic acid. Pravachol Co-Administered With Buffered Aspirin The pharmacokinetic interaction of buffered aspirin (325 mg) and pravastatin (40 mg) were studied in a single-dose crossover study in healthy subjects. Co-administration with buffered aspirin had no significant effect on the C max and AUC of pravastatin. Similarly, co-administration with pravastatin had no significant effect on the C max and AUC of salicylate. Clinical Studies Pravachol Secondary Prevention of Cardiovascular Events In the Long-term Intervention with Pravastatin in Ischemic Disease (LIPID) 1 study, the effect of PRAVACHOL, 40 mg daily, was assessed in 9014 patients (7498 men; 1516 women; 3514 elderly patients [age ≥65 years]; 782 diabetic patients) who had experienced either myocardial infarction (MI) (5754 patients) or had been hospitalized for unstable angina pectoris (3260 patients) in the preceding 3-36 months. Patients in this multicenter, double-blind, placebo-controlled study participated for an average of 5.6 years (median of 5.9 years) and at randomization had Total-C between 114 and 563 mg/dL (mean 219 mg/dL), LDL-C between 46 and 274 mg/dL (mean 150 mg/dL), triglycerides between 35 and 2710 mg/dL (mean 160 mg/dL), and HDL-C between 1 and 103 mg/dL (mean 37 mg/dL). At baseline, 82% of patients were receiving aspirin and 76% were receiving antihypertensive medication. Treatment with PRAVACHOL significantly reduced the risk for total mortality by reducing coronary death (see Table 2 ). The risk reduction due to treatment with PRAVACHOL on coronary heart disease (CHD) mortality was consistent regardless of age. PRAVACHOL significantly reduced the risk for total mortality (by reducing CHD death) and CHD events (CHD mortality or nonfatal MI) in patients who qualified with a history of either MI or hospitalization for unstable angina pectoris. Table 2: LIPID - Primary and Secondary Endpoints Event Pravastatin 40 mg (N=4512) Placebo (N=4502) Risk Reduction (95% CI) P -value Primary Endpoint Number (%) of Subjects *The risk reduction due to treatment with PRAVACHOL was consistent in both sexes. CHD mortality * 287 (6.4) 373 (8.3) 24% (12, 35) 0.0004 Secondary Endpoints Number (%) of Subjects Total mortality 498 (11.0) 633 (14.1) 23% (13, 31) <0.0001 CHD mortality or nonfatal MI 557 (12.3) 715 (15.9) 24% (15, 32) <0.0001 Myocardial revascularization procedures (CABG or PTCA) 584 (12.9) 706 (15.7) 20% (10, 28) <0.0001 Stroke All-cause Non-hemorrhagic 169 (3.7) 154 (3.4) 204 (4.5) 196 (4.4) 19% (0, 34) 23% (5, 38) 0.048 0.015 Cardiovascular mortality 331 (7.3) 433 (9.6) 25% (13, 35) <0.0001 In the Cholesterol and Recurrent Events (CARE) 2 study, the effect of PRAVACHOL, 40 mg daily, on coronary heart disease death and nonfatal MI was assessed in 4159 patients (3583 men and 576 women) who had experienced a myocardial infarction in the preceding 3-20 months and who had normal (below the 75 th percentile of the general population) plasma Total-C levels. Patients in this double-blind, placebo-controlled study participated for an average of 4.9 years and had a mean baseline Total-C of 209 mg/dL. LDL-C levels in this patient population ranged from 101 mg/dL–180 mg/dL (mean 139 mg/dL). At baseline, 84% of patients were receiving aspirin and 82% were taking antihypertensive medications. Median (25 th , 75 th percentile) percent changes from baseline after 6 months of pravastatin treatment in Total-C, LDL-C, TG, and HDL were -22.0 (-28.4, -14.9), -32.4 (-39.9, -23.7), -11.0 (-26.5, 8.6), and 5.1 (-2.9, 12.7), respectively. Treatment with PRAVACHOL significantly reduced the rate of first recurrent coronary events (either CHD death or nonfatal MI), the risk of undergoing revascularization procedures (percutaneous transluminal coronary angioplasty [PTCA], coronary artery bypass graft [CABG]), and the risk for stroke or transient ischemic attack (TIA) (see Table 3 ). Table 3: CARE - Primary and Secondary Endpoints Event Pravastatin 40 mg (N=2081) Placebo (N=2078) Risk Reduction (95% CI) P -value Primary Endpoint Number (%) of Subjects *The risk reduction due to treatment with PRAVACHOL was consistent in both sexes. CHD mortality or nonfatal MI * 212 (10.2) 274 (13.2) 24% (9, 36) 0.003 Secondary Endpoints Number (%) of Subjects Myocardial revascularization procedures (CABG or PTCA) 294 (14.1) 391 (18.8) 27% (15, 37) <0.001 Stroke or TIA 93 (4.5) 124 (6.0) 26% (4, 44) 0.029 Primary Hypercholesterolemia (Fredrickson Type IIa and IIb) PRAVACHOL (pravastatin sodium) is highly effective in reducing Total-C, LDL-C and triglycerides (TG) in patients with heterozygous familial, presumed familial combined and non-familial (non-FH) forms of primary hypercholesterolemia, and mixed dyslipidemia. A therapeutic response is seen within 1 week, and the maximum response usually is achieved within 4 weeks. This response is maintained during extended periods of therapy. A single daily dose is as effective as the same total daily dose given twice a day. In multicenter, double-blind, placebo-controlled studies of patients with primary hypercholesterolemia, treatment with pravastatin in daily doses ranging from 10 mg to 40 mg consistently and significantly decreased Total-C, LDL-C, TG, and Total-C/HDL-C and LDL-C/HDL-C ratios (see Table 4 ). In a pooled analysis of two multicenter, double-blind, placebo-controlled studies of patients with primary hypercholesterolemia, treatment with pravastatin at a daily dose of 80 mg (N=277) significantly decreased Total-C, LDL-C, and TG. The 25 th and 75 th percentile changes from baseline in LDL-C for pravastatin 80 mg were -43% and -30%. The efficacy results of the individual studies were consistent with the pooled data (see Table 4 ). Treatment with PRAVACHOL modestly decreased VLDL-C, and PRAVACHOL across all doses produced variable increases in HDL-C (see Table 4 ). Table 4: Primary Hypercholesterolemia Studies: Dose Response of PRAVACHOL Once Daily Administration Dose Total-C LDL-C HDL-C TG Mean Percent Changes From Baseline After 8 Weeks* * a multicenter, double-blind, placebo-controlled study **pooled analysis of 2 multicenter, double-blind, placebo-controlled studies Placebo (N=36) -3% -4% +1% -4% 10 mg (N=18) -16% -22% +7% -15% 20 mg (N=19) -24% -32% +2% -11% 40 mg (N=18) -25% -34% +12% -24% Mean Percent Changes From Baseline After 6 Weeks** Placebo (N=162) 0% -1% -1% +1% 80 mg (N=277) -27% -37% +3% -19% Buffered Aspirin Ischemic Stroke and Transient Ischemic Attack (TIA) In clinical trials of subjects with TIAs due to fibrin platelet emboli or ischemic stroke, aspirin has been shown to significantly reduce the risk of the combined endpoint of stroke or death and the combined endpoint of TIA, stroke, or death by about 13-18%. Prevention of Recurrent MI and Unstable Angina Pectoris These indications are supported by the results of six large, randomized, multicenter, placebo-controlled trials of predominantly male post-MI subjects and one randomized placebo-controlled study of men with unstable angina pectoris. Aspirin therapy in MI subjects was associated with a significant reduction (about 20%) in the risk of the combination endpoint of subsequent death and/or nonfatal reinfarction in these patients. In aspirin-treated unstable angina patients, the event rate was reduced to 5% from the 10% rate in the placebo group. Chronic Stable Angina Pectoris In a randomized, multicenter, double-blind trial designed to assess the role of aspirin for prevention of MI in patients with chronic stable angina pectoris, aspirin significantly reduced the primary combined endpoint of nonfatal MI, fatal MI, and sudden death by 34%. The secondary endpoint for vascular events (first occurrence of MI, stroke, or vascular death) was also significantly reduced (32%). Revascularization Procedures Most patients who undergo coronary artery revascularization procedures have already had symptomatic coronary artery disease for which aspirin is indicated. Similarly, patients with lesions of the carotid bifurcation sufficient to require carotid endarterectomy are likely to have had a precedent event. Aspirin is recommended for patients who undergo revascularization procedures if there is a preexisting condition for which aspirin is already indicated. Pravachol Co-Administered With Buffered Aspirin Five PRAVACHOL secondary prevention studies (LIPID, CARE, REGRESS, PLAC I, and PLAC II) were combined in a meta-analysis to assess the independent effects of the concomitant use of pravastatin and aspirin when compared to pravastatin alone and aspirin alone on cardiovascular outcomes. 1-5 These studies enrolled a total of 14,617 patients who were randomized to receive pravastatin or placebo. Within each randomized group, approximately 20% were not concurrently receiving aspirin. Patients enrolled into these studies included women (15%) and individuals greater than 65 years of age (35%). The independent effects of aspirin and pravastatin on cardiovascular events were seen when the population was grouped according to age and gender. Consistency of these outcomes according to race could not be determined, since information on race was not uniformly collected across all five studies. Baseline histories included previous MI (72%) and revascularization (43%). Each component of the pravastatin/aspirin combination contributed to the outcome benefits when these benefits were retrospectively defined as: the composite endpoint of fatal or nonfatal MI the composite outcome of CHD death or nonfatal MI ischemic stroke the composite outcome of CHD death, nonfatal MI or revascularization procedures the composite endpoint of CHD death, nonfatal MI, revascularization procedures or ischemic stroke Table 5 compares the cardiovascular events seen in subjects receiving the combination of pravastatin/aspirin and aspirin alone, derived from the randomized cohort in the five studies. Table 5: Number of Events and Risk Reduction of Pravastatin/Aspirin Compared to Aspirin Alone Event Pravastatin/ Aspirin (N=5888) Placebo/ Aspirin (N=5833) Risk Reduction (95% CI) Number (%) of Subjects Fatal or nonfatal MI 445 (7.6) 626 (10.7) 31% (22, 39) CHD death or nonfatal MI 597 (10.1) 830 (14.2) 31% (23, 38) Ischemic stroke 134 (2.3) 183 (3.1) 29% (12, 43) CHD death, nonfatal MI or revascularization procedures 1218 (20.7) 1543 (26.5) 24% (18, 30) CHD death, nonfatal MI, revascularization procedures or ischemic stroke 1314 (22.3) 1661 (28.5) 24% (19, 30) Table 6 compares the cardiovascular events seen in subjects receiving the combination of pravastatin/aspirin and pravastatin alone, derived from the non-randomized cohort not receiving aspirin in the five trials. Table 6: Number of Events and Risk Reduction of Pravastatin/Aspirin Compared to Pravastatin Alone Event Pravastatin/ Aspirin (N=5888) Pravastatin/ Placebo (N=1436) Risk Reduction (95% CI) Number (%) of Subjects Fatal or nonfatal MI 445 (7.6) 125 (8.7) 26% (10, 39) CHD death or nonfatal MI 597 (10.1) 196 (13.7) 37% (25, 46) Ischemic stroke 134 (2.3) 44 (3.1) 31% (3, 51) CHD death, nonfatal MI or revascularization procedures 1218 (20.7) 308 (21.5) 11% (-0.6, 22) CHD death, nonfatal MI, revascularization procedures or ischemic stroke 1314 (22.3) 341 (23.8) 14% (2, 23) In a supportive analysis, the effects of pravastatin/aspirin were sustained through five years of follow-up.