SULAR — nisoldipine tablet, film coated, extended release
Physicians Total Care, Inc.
Extended Release Tablets
For Oral Use
SULAR® (nisoldipine) is an extended release tablet dosage form of the dihydropyridine calcium channel blocker nisoldipine. Nisoldipine is 3,5-pyridinedicarboxylic acid, 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-, methyl 2-methylpropyl ester, C20 H24 N2 O6 , and has the structural formula:
Nisoldipine is a yellow crystalline substance, practically insoluble in water but soluble in ethanol. It has a molecular weight of 388.4. SULAR tablets comprise three layers: a top barrier layer, a middle layer containing nisoldipine, and a bottom barrier layer. The erodible barrier layers and the hydrogel middle layer provide for the controlled release of the drug. SULAR tablets contain either 8.5, 17, 25.5 or 34 mg of nisoldipine for once-a-day oral administration.
Inactive ingredients in the formulation include: Hypromellose,hypromellose phthalate, lactose,glyceryl behenate, povidone, magnesium stearate, silicon dioxide,methacrylic acid copolymer, and sodium lauryl sulfate. Inactive ingredients in the film coating include: polydextrose, titanium dioxide, hypromellose, polyethylene glycol, iron oxide, and carnauba wax. Additionally, the 17 mg formulation contains FD&C Yellow #5.
Nisoldipine is a member of the dihydropyridine class of calcium channel antagonists (calcium ion antagonists or slow channel blockers) that inhibit the transmembrane influx of calcium into vascular smooth muscle and cardiac muscle. It reversibly competes with other dihydropyridines for binding to the calcium channel. Because the contractile process of vascular smooth muscle is dependent upon the movement of extracellular calcium into the muscle through specific ion channels, inhibition of the calcium channel results in dilation of the arterioles. In vitro studies show that the effects of nisoldipine on contractile processes are selective, with greater potency on vascular smooth muscle than on cardiac muscle. Although, like other dihydropyridine calcium channel blockers, nisoldipine has negative inotropic effects in vitro , studies conducted in intact anesthetized animals have shown that the vasodilating effect occurs at doses lower than those that affect cardiac contractility.
The effect of nisoldipine on blood pressure is principally a consequence of a dose-related decrease of peripheral vascular resistance. While nisoldipine, like other dihydropyridines, exhibits a mild diuretic effect, most of the antihypertensive activity is attributed to its effect on peripheral vascular resistance.
Nisoldipine pharmacokinetics are independent of the dose across the clicinal dosage range of 17 to 51 mg, with plasma concentrations proportional to dose. Nisoldipine accumulation, during multiple dosing, is predictable from a single dose. Nisoldipine is relatively well absorbed into the systemic circulation with 87% of the radiolabeled drug recovered in urine and feces. The absolute bioavailability of nisoldipine is about 5%. Nisoldipine’s low bioavailability is due, in part, to pre-systemic metabolism in the gut wall, and this metabolism decreases from the proximal to the distal parts of the intestine. A pronounced food-effect is observed when SULAR is administered with a high-fat meal resulting in an increased peak concentration (Cmax ) of up to 245%. Total exposure (AUC) is decreased by 25%. As a result, SULAR should be taken on an empty stomach (1 hour before or 2 hours after a meal).
Maximal plasma concentrations of nisoldipine are reached at 9.2 ± 5.1 hours. The terminal elimination half-life (reflecting post absorption clearance of nisoldipine) ranges from 13.7 ± 4.3 hours. After oral administration, the concentration of (+)-nisoldipine, the active enantiomer, is about 6 times higher than the inactive (-) -nisoldipine enantiomer. The plasma protein binding of nisoldipine is very high, with less than 1% unbound over the plasma concentration range of 100 ng/mL to 10 mcg/mL.
Nisoldipine is highly metabolized; 5 major urinary metabolites have been identified. Although 60 — 80% of an oral dose undergoes urinary excretion, only traces of unchanged nisoldipine are found in urine. The major biotransformation pathway appears to be the hydroxylation of the isobutyl ester. A hydroxylated derivative of the side chain, present in plasma at concentrations approximately equal to the parent compound, appears to be the only active metabolite, and has about 10% of the activity of the parent compound. Cytochrome P450 enzymes are believed to play a major role in the metabolism of nisoldipine. The particular isoenzyme system responsible for its metabolism has not been identified, but other dihydropyridines are metabolized by cytochrome P450 IIIA4. Nisoldipine should not be administered with grapefruit juice, as this has been shown, in a study of 12 subjects, to interfere with nisoldipine metabolism, resulting in a mean increase in Cmax of about 3-fold (ranging up to about 7-fold) and AUC of almost 2-fold (ranging up to about 5-fold). A similar phenomenon has been seen with several other dihydropyridine calcium channel blockers.
Because renal elimination is not an important pathway, bioavailability and pharmacokinetics of SULAR were not significantly different in patients with various degrees of renal impairment. Dosing adjustments in patients with mild to moderate renal impairment are not necessary.
Elderly patients have been found to have 2 to 3 fold higher plasma concentrations (Cmax and AUC) than young subjects. This should be reflected in more cautious dosing (See DOSAGE AND ADMINISTRATION).
In patients with liver cirrhosis given a dose bioequivalent to 8.5 mg SULAR, plasma concentrations of the parent compound were 4 to 5 times higher than those in healthy young subjects. Lower starting and maintenance doses should be used in cirrhotic patients (See DOSAGE AND ADMINISTRATION).
The effect of gender or race on the pharmacokinetics of nisoldipine has not been investigated.
Hypertension does not significantly alter the pharmacokinetics of nisoldipine.
Administration of a single dose of nisoldipine leads to decreased systemic vascular resistance and blood pressure with a transient increase in heart rate. The change in heart rate is greater with immediate release nisoldipine preparations. The effect on blood pressure is directly related to the initial degree of elevation above normal. Chronic administration of nisoldipine results in a sustained decrease in vascular resistance and small increases in stroke index and left ventricular ejection fraction. A study of the immediate release formulation showed no effect of nisoldipine on the renin-angiotensin-aldosterone system or on plasma norepinephrine concentration in normals. Changes in blood pressure in hypertensive patients given SULAR were dose related over the clinical dosage range.
Nisoldipine does not appear to have significant negative inotropic activity in intact animals or humans, and did not lead to worsening of clinical heart failure in three small studies of patients with asymptomatic and symptomatic left ventricular dysfunction. There is little information, however, in patients with severe congestive heart failure, and all calcium channel blockers should be used with caution in any patient with heart failure.
Nisoldipine has no clinically important chronotropic effects. Except for mild shortening of sinus cycle, SA conduction time and AH intervals, single oral doses up to 20 mg of immediate release nisoldipine did not significantly change other conduction parameters. Similar electrophysiologic effects were seen with single IV doses, which could be blunted in patients pre-treated with beta-blockers. Dose and plasma level related flattening or inversion of T-waves have been observed in a few small studies. Such reports were concentrated in patients receiving rapidly increased high doses in one study; the phenomenon has not been a cause of safety concern in large clinical trials.
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