4. DRUG PROFILE Atorvastatin calcium

Transcription

1 4. DRUG PROFILE 4.1. Atorvastatin calcium (USP, Clarkes Analysis and Martindale) The Atorvastatin calcium component of is chemically described as [R-(R*,R*)]-2-(4- fluorophenyl)-β,a-dihydroxy-5-(1-methylethyl)-3-phenyl-4[(phenylamino) carbonyl]-1h-pyrrole- 1-heptanoic acid, calcium salt (2:1) trihydrate. Its empirical formula is (C 33 H 34 FN 2 O 5 ) 2 Ca 3H 2 O. The Atorvastatin was selected for the development of solid self-nanoemulsifying approaches. Atorvastatin a hypolipidemic agent and is official in USP. The profile of drug is described as follows: Description (USP, Clarkes Analysis and Martindale) Mol. Structure Chemical Name Calcium (βr,δr)-2-(p-fluorophenyl)-β,δ- dihydroxy-5-isopropyl-3-phenyl-4- (phenylcarbamoyl)pyrrole-1-heptanoicacid (1:2) trihydrate Molecular Formula [C 33 H 35 FN 2 O 5 ] 2 Ca.3H 2 O Generic Name Atorvastatin calcium Molecular Weight g/mol Category Cardiovascular Agents Sub-category HMG-CoA Reductase Inhibitor Percentage Purity 98.0% % Calcium percentage % Water 7% Loss on drying 0.5% IFTM, University, Moradabad Page 4.1 of 4.12

2 Physical properties (USP, Clarkes Analysis and Martindale) Appearance White to off white amorphous powder Solubility Freely soluble in methanol and soluble in dimethylsulphoxide (DMSO) and dimethyl formamide (DMF); insoluble in aqueous solution with ph less than 4.0. It is very slightly soluble in distilled water, Phosphate buffer (7.4) and acetonitrile; slightly soluble in ethanol µg/ml (ph 2.1), 1.23 mg/ml (ph 6.0) Stability Stable under ordinary conditions Pka Log P 6.36 (Octanol/Water) Melting point C Storage To be stored in well closed, away from heat and damp places Pharmacology of Atorvastatin (USP, Clarke s analysis and Martindale) Atorvastatin, a synthetic cholesterol-lowering agent, is a medicine called HMG-CoA (3 hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitor. This enzyme is involved cholesterol biosynthesis by catalyzing the conversion reaction of HMG-CoA to mevalonate. The function of lowering the amount of cholesterol leads to the result in clearing the LDP (low-density lipoprotein) cholesterol in the blood by increased LDL receptors. The calcium salt of Atorvastatin is used in the treatment of primary hypercholesterolemia and dyslipidemia Mechanism of Action (Drugs.com) Atorvastatin lowers plasma cholesterol and lipoprotein levels by inhibiting HMG-CoA reductase and cholesterol synthesis in the liver and by increasing the number of hepatic LDL receptors on the cell-surface to enhance uptake and catabolism of LDL; Atorvastatin also reduces LDL production and the number of LDL particles. IFTM, University, Moradabad Page 4.2 of 4.12

3 Biopharmaceutics and Pharmacokinetics (D. Williams and J. Feely, 2002) Absorption After oral administration alone, Atorvastatin is rapidly absorbed; maximum plasma concentrations occur within 1 to 2 hrs. Extent of absorption increases in proportion to Atorvastatin dose. The absolute bioavailability of Atorvastatin (parent drug) is approximately 14% and the systemic availability of HMG-CoA reductase inhibitory activity is approximately 30%. The low systemic availability is attributed to presystemic clearance in gastrointestinal mucosa and/or hepatic first-pass metabolism. Although food decreases the rate and extent of drug absorption by approximately 25% and 9%, respectively, as assessed by Cmax and AUC, LDL-C reduction is similar whether Atorvastatin is given with or without food. Plasma Atorvastatin concentrations are lower (approximately 30% for Cmax and AUC) following evening drug administration compared with morning. However, LDL-C reduction is the same regardless of the time of day of drug administration. A blood/plasma ratio of approximately 0.25 indicates poor drug penetration into red blood cells. Based on observations in rats, Atorvastatin calcium is likely to be secreted in human milk Distribution (drugs.com) Mean volume of distribution of Atorvastatin is approximately 381 liters. Atorvastatin is = 98% bound to plasma proteins. A blood/plasma ratio of approximately 0.25 indicates poor drug penetration into red blood cells. Based on observations in rats, Atorvastatin calcium is likely to be secreted in human milk Metabolism(A.E. Black, and R. N. Hayes, 1999) Atorvastatin is extensively metabolized to ortho- and parahydroxylated derivatives and various beta-oxidation products. In vitro inhibition of HMG-CoA reductase by ortho- and parahydroxylated metabolites is equivalent to that of Atorvastatin. Approximately 70% of circulating inhibitory activity for HMG-CoA reductase is attributed to active metabolites. In vitro studies suggest the importance of Atorvastatin metabolism by cytochrome P450 3A4, consistent with increased plasma concentrations of Atorvastatin in humans following coadministration with erythromycin, a known inhibitor of this isozyme. IFTM, University, Moradabad Page 4.3 of 4.12

4 Elimination (A.E. Black, and R. N. Hayes, 1999) Atorvastatin and its metabolites are eliminated primarily in bile following hepatic and/or extra-hepatic metabolism; however, the drug does not appear to undergo enterohepatic recirculation. Mean plasma elimination half-life of Atorvastatin in humans is approximately 14 hrs, but the half-life of inhibitory activity for HMG-CoA reductase is 20 to 30 hrs due to the contribution of active metabolites. Less than 2% of a dose of Atorvastatin is recovered in urine following oral administration. Pharmacokinetic parameters of Atorvastatin calcium (D. Williams and J. Feely, 2002) S. No Parameters Result 1 Oral absorption > 90% 2 Presystemic metabolism 80 % 3 Plasma protein binding 98% 4 Volume of distribution 565 L Distribution in blood (Blood cells: plasma) 6 Plasma half life 14 R Contra-Indications (C.M. Pfeiffer, and S. Kazenoff, 1998) Atherosclerosis is a chronic process and discontinuation of lipid-lowering drugs during pregnancy should have little impact on the outcome of long-term therapy of primary hypercholesterolemia. Cholesterol and other products of cholesterol biosynthesis are essential components for fetal development (including synthesis of steroids and cell membranes). Since HMG-CoA reductase inhibitors decrease cholesterol synthesis and possibly the synthesis of other biologically active substances derived from cholesterol, they may cause fetal harm when administered to pregnant women. Therefore, HMG-CoA reductase inhibitors are contraindicated during pregnancy and in nursing mothers. If the patient becomes pregnant while taking this drug, therapy should be discontinued and the patient apprised of the potential hazard to the fetus. IFTM, University, Moradabad Page 4.4 of 4.12

5 Precautions (D.M. Black,. and R. G. Bakker-Arkema, 1998) Statins should not be given to patients with active liver disease or unexplained persistently raised serum-aminotransferase concentrations and should be discontinued if marked or persistent increases in serum-aminotransferase concentrations occur. They should be avoided during pregnancy since there is a possibility that they could interfere with fetal sterol synthesis; there have been a number of reports of congenital abnormalities associated with statins. Statins may cause myopathy and rhabdomyolysis, especially at higher doses, and they should be used with caution in patients at risk of rhabdomyolysis, and particularly in patients taking drugs that increase plasma concentrations of the statin; the statin should be discontinued if creatine phosphokinase increases significantly or if myopathy is diagnosed. Some statins, such as Fluvastatin, Pravastatin, rosuvastatin, and Simvastatin, should be used with caution in patients with severe renal impairment Adverse reactions (D. Williams, and J. Feely, 2002). The commonest adverse effects of therapy with Atorvastatin and other statins are gastrointestinal disturbances. Other adverse effects reported include headache, skin rashes, dizziness, blurred vision, insomnia, and dysgeusia. Reversible increases in serum-aminotransferase concentrations may occur and liver function should be assessed before treatment is initiated and then monitored periodically until one year after the last elevation in dose. Hepatitis and pancreatitis have been reported. Hypersensitivity reactions including anaphylaxis and angioedema have also occurred. Myopathy, characterized by myalgia and muscle weakness and associated with increased creatine phosphokinase concentrations, has been reported, especially in patients taking statins concurrently with Cyclosporine, fibric acid derivatives, or nicotinic acid. Rarely, rhabdomyolysis with acute renal failure may develop Drug-interactions (D. Williams and J. Feely, 2002). The drug interactions with Atorvastatin and other statins is the development of myopathy or rhabdomyolysis. Drugs that can cause myopathy IFTM, University, Moradabad Page 4.5 of 4.12

6 when given alone increase the risk of myopathy with all statins; these drugs include fibric acid derivatives (fibrates or gemfibrozil), and nicotinic acid. The risk of myopathy is also increased by drugs that increase the plasma levels of statins by inhibiting their metabolism. Since the statins have different metabolic pathways, these interactions depend on the individual drug concerned. Simvastatin is metabolized by the cytochrome P450 isoenzyme CYP3A4, as are Atorvastatin and Lovastatin, and interactions may occur with drugs that inhibit this enzyme, including Cyclosporine, Itraconazole, Ketoconazole, erythromycin, Clarithromycin, HIV-protease inhibitors, Nefazodone, Amiodarone, and Verapamil; there may also be a similar interaction with grapefruit juice. Statins may also have effects on other drugs. IFTM, University, Moradabad Page 4.6 of 4.12

7 4.2. Amlodipine Besylate (European pharmacopoeia; Pfizer Laboratories. 2006) Description Amlodipine besylate Dihyrropridine derivative Chemical Name 3-ethyl 5-methyl(4RS)-2-[(2- aminoethoxy)methyl]-4-(2 chlorophenyl)-6- methyl-1,4-dihydropyridine-3, 5- dicarboxylate benzenesulfonate Molecular (free base 408.9) Weight Structural Formula Physical properties Amlodipine besylate is a white crystalline powder and is slightly soluble in water and sparingly soluble in ethanol. In addition to Amlodipine besylate, each tablet contains the following inactive ingredients: lactose, microcrystalline cellulose, maize starch and magnesium stearate Pharmacological actions (Pfizer Laboratories, 2006) Amlodipine is a calcium ion influx inhibitor (slow channel blocker or calcium ion antagonist) and inhibits the transmembrane influx of calcium ions into cardiac and vascular smooth muscle. Experimental data suggest that Amlodipine binds to both dihyrropridine and non-dihyrropridine binding sites. The contractile processes of cardiac muscle IFTM, University, Moradabad Page 4.7 of 4.12

8 and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells. Negative ionotropic effects can be detected in vitro but such effects have not been seen in intact animals at therapeutic doses. Serum calcium concentration is not affected by Amlodipine. Within the physiologic ph range, Amlodipine is an ionized compound (pk a =8.6), and its kinetic interaction with the calcium channel receptor is characterized by a gradual rate of association and dissociation with the receptor binding site, resulting in a gradual onset of effect. Amlodipine is a peripheral arterial vasodilator that acts directly on vascular smooth muscle to cause a reduction in peripheral vascular resistance and reduction in blood pressure. The precise mechanism by which Amlodipine relieves angina has not been fully determined but Amlodipine reduces the total ischaemic burden by the following two actions: Amlodipine dilates peripheral arterioles and thus reduces the total peripheral resistance (after load) against which the heart works. Since the heart rate remains stable, this unloading of the heart reduces myocardial energy consumption and oxygen requirements. Amlodipine has been shown to block constriction in main coronary arteries and coronary arterioles, induced by calcium, potassium, adrenaline, serotonin and thromboxane A2 analogue both in normal and in ischaemic regions Haemodynamic (D. Murdoch and R.C. Heel, 1991) Following administration of therapeutic doses to patients with hypertension, Amlodipine produces vasodilation resulting in a reduction of supine and standing blood pressures. These decreases in blood pressure are not accompanied by a significant change in heart rate or plasma catecholamine levels with chronic dosing. Although the acute intravenous administration of Amlodipine decreased arterial blood pressure and increased heart rate in hemodynamic studies of patients with chronic stable angina, chronic administration of oral Amlodipine in clinical trials did not lead to clinically significant changes in heart rate or blood IFTM, University, Moradabad Page 4.8 of 4.12

9 pressures in normotensive patients with angina. With chronic once daily oral administration, antihypertensive effectiveness is maintained for at least 24 hours. Plasma concentrations correlate with effect in both young and elderly patients. The magnitude of reduction in blood pressure with Amlodipine is also correlated with the height of pretreatment elevation; thus, individuals with moderate hypertension (diastolic pressure mm Hg) had about a 50% greater response than patients with mild hypertension (diastolic pressure mm Hg). Normotensive subjects experienced no clinically significant change in blood pressures (±1/2 mmhg). As with other calcium channel blockers, haemodynamic measurements of cardiac function at rest and during exercise (or pacing) in patients with normal ventricular function treated with Amlodipine have generally demonstrated a small increase in cardiac index without significant influence on dp/dt or on left ventricular end diastolic pressure or volume. In haemodynamic studies, Amlodipine has not been associated with a negative inotropic effect when administered in the therapeutic dose range to intact animals and man, even when coadministered with beta-blockers to man. Similar findings, however, have been observed in normal s or well-compensated patients with heart failure with agents possessing significant negative inotropic effects. In hypertensive patients with normal renal function, therapeutic doses of Amlodipine resulted in a decrease in renal vascular resistance and an increase in glomerular filtration rate and effective renal plasma flow without change in filtration fraction or Proteinuria Pharmacokinetics and Metabolism (D. Murdoch, R. C. Heel, 1991; R.A. Burges, and M. G. Dodd, 1990) After oral administration of therapeutic doses, Amlodipine is well absorbed with peak blood levels between 6-12 hrs post dose. This may reflect significant initial uptake by the liver, followed by a phase of redistribution. This interval is shorter (2-8 hrs) in patients with hepatic insufficiency. Absolute bioavailability has been estimated to be between 64 and 90%. The bioavailability of Amlodipine is not altered by the presence of food. The volume of distribution is approximately 20 L/kg. The terminal plasma IFTM, University, Moradabad Page 4.9 of 4.12

10 elimination half life is about hours and is consistent with once daily dosing. Steady state plasma levels are reached after 7-8 days of consecutive dosing. In elderly hypertensive patients (mean age 69 years) there was a decrease in clearance of Amlodipine from plasma as compared to young volunteers (mean age 36 years) with a resulting increase in the area under the curve (AUC) of about 60%. Amlodipine is extensively metabolized by the liver to inactive metabolites with 10% of the parent compound and 60% of metabolites excreted in the urine. In-vitro studies have shown that approximately 97.5% of circulating Amlodipine is bound to plasma proteins Indications (Anon, et.al., 1992) APO-Amlodipine is indicated for the first line treatment of hypertension and can be used as the sole agent to control blood pressure in the majority of patients. Patients not adequately controlled on a single antihypertensive agent may benefit from the addition of APO-Amlodipine, which has been used in combination with a thiazide diuretic, beta adrenoceptor blocking agent or an angiotensin-converting enzyme inhibitor. APO-Amlodipine is indicated for the first line treatment of chronic stable angina. APO-Amlodipine may be used alone, as monotherapy or in combination with other antianginal drugs Contraindications (P.A. Meredith, and H.L. Elliott, 1992) APO-Amlodipine is contraindicated in patients with a known sensitivity to Amlodipine, dihydropyridines, or any of the inactive ingredients Precautions (M.H. Alderman et.al., 1992; J. Vincent, and S. Harris, 2002) Rarely patients, particularly those with severe obstructive coronary artery disease, have developed documented increased frequency, duration and/or severity of angina on starting calcium channel blocker therapy or at the time of dosage increase. The mechanism of this effect has not been elucidated. APO-Amlodipine should be used with caution in the presence of a fixed left ventricular outflow obstruction (aortic stenosis). IFTM, University, Moradabad Page 4.10 of 4.12

11 Interactions with other medicines (Pfizer Labs., 2007) Amlodipine has been safely administered with thiazide diuretics, betablockers, angiotensin converting enzyme inhibitors, long-acting nitrates, sublingual nitroglycerine, non-steroidal anti-inflammatory drugs, antibiotics and oral hypoglycemic drugs. Special studies have indicated that the co-administration of Amlodipine with digoxin did not change serum digoxin levels or digoxin renal clearance in normal volunteers, and that co-administration of Cimetidine did not alter the pharmacokinetics of Amlodipine; and that co-administration with Warfarin did not change the Warfarin prothrombin response time. In-vitro data from studies with human plasma indicate that Amlodipine has no effect on protein binding of the drugs tested (Digoxin, Phenytoin, Warfarin or Indomethacin) Adverse effects (Novartis Pharmaceuticals Corp, 2008) Amlodipine has been evaluated for safety in more than patients in clinical trials worldwide. In general, treatment with Amlodipine was well-tolerated at doses up to 10 mg daily. Most adverse reactions reported during therapy with Amlodipine were of mild or moderate severity. In controlled clinical trials directly comparing Amlodipine (N=1730) in doses up to 10 mg to placebo (N=1250), discontinuation of Amlodipine due to adverse reactions was required in only about 1.5% of patients and was not significantly different from placebo (about 1%). Amlodipine therapy has not been associated with clinically significant changes in routine laboratory tests. No clinically relevant changes were noted in serum potassium, serum glucose, total triglycerides, total cholesterol, HDL cholesterol, uric acid, blood urea nitrogen or creatinine or liver function tests Dosage and Administration (Daiichi Sankyo, Inc. 2008) For hypertension or angina the usual initial dose is 2.5 to 5 mg once daily which may be increased to a maximum dose of 10 mg depending on the individual patient's response. Small, fragile or elderly individuals, or patients with hepatic insufficiency should be started on 2.5 mg once daily and this dose may be used when adding amlodipine to other antihypertensive therapy. Dosage should be adjusted according to each patient's need. In general, titration should proceed over 7 to 14 days so that the physician can fully assess the patient's response to each IFTM, University, Moradabad Page 4.11 of 4.12

12 dose level. Titration may proceed more rapidly, however, if clinically warranted, provided the patient is assessed frequently Over dosage (Daiichi Sankyo, Inc. 2008) Dysrhythmias may occur following overdose with any calcium antagonists. Hypotension and bradycardia are usually seen within 1 to 5 hrs following overdose. Hypotension can persist for longer than 24 hrs despite treatment. Cardiac rhythm disturbances have been noted to persist for up to 7 days. Marked and probably prolonged systemic hypotension up to and including shock with fatal outcome have been reported. Reports of intentional over dosage include a patient who ingested 250 mg and was asymptomatic and was not hospitalized; another (120 mg) was hospitalized, underwent gastric lavage and remained normotensive; a third one (105 mg) was hospitalized and had hypotension (90/50 mm Hg) which normalized following plasma expansion. If massive overdose should occur, active cardiac and respiratory monitoring should be instituted. Frequent blood pressure measurements are essential. Should hypotension occur, cardiovascular support including elevation of the extremities and the judicious administration of fluids should be initiated. If hypotension remains unresponsive to these conservative measures, administration of vasopressors (such as phenylephrine), should be considered with attention to circulating volume and urine output. Intravenous calcium may help to reverse the effects of calcium entry blockade Storage (Pfizer Labs 2007) Store below 25 C. Store in the original package. IFTM, University, Moradabad Page 4.12 of 4.12