Colestipol Hydrochloride

COLESTIPOL HYDROCHLORIDE — colestipol hydrochloride tablet
Physicians Total Care, Inc.

DESCRIPTION

The active ingredient in micronized colestipol hydrochloride tablets is micronized colestipol hydrochloride, which is a lipid lowering agent for oral use. Colestipol is an insoluble, high molecular weight basic anion-exchange copolymer of diethylenetriamine and 1-chloro-2, 3-epoxypropane, with approximately 1 out of 5 amine nitrogens protonated (chloride form). It is a light yellow water-insoluble resin which is hygroscopic and swells when suspended in water or aqueous fluids.

Each micronized colestipol hydrochloride tablet contains one gram of micronized colestipol hydrochloride. Micronized colestipol hydrochloride tablets are light yellow in color and are tasteless and odorless. Inactive ingredients: cellulose acetate phthalate, glyceryl triacetate, carnauba wax, hypromellose, magnesium stearate, povidone, silicon dioxide. Micronized colestipol hydrochloride tablets contain no calories.

CLINICAL PHARMACOLOGY

Cholesterol is the major, and probably the sole precursor of bile acids. During normal digestion, bile acids are secreted via the bile from the liver and gall bladder into the intestines. Bile acids emulsify the fat and lipid materials present in food, thus facilitating absorption. A major portion of the bile acids secreted is reabsorbed from the intestines and returned via the portal circulation to the liver, thus completing the enterohepatic cycle. Only very small amounts of bile acids are found in normal serum.

Colestipol hydrochloride binds bile acids in the intestine forming a complex that is excreted in the feces. This nonsystemic action results in a partial removal of the bile acids from the enterohepatic circulation, preventing their reabsorption. Since colestipol hydrochloride is an anion exchange resin, the chloride anions of the resin can be replaced by other anions, usually those with a greater affinity for the resin than the chloride ion.

Colestipol hydrochloride is hydrophilic, but it is virtually water insoluble (99.75%) and it is not hydrolyzed by digestive enzymes. The high molecular weight polymer in colestipol hydrochloride apparently is not absorbed. In humans, less than 0.17% of a single 14 C-labeled colestipol hydrochloride dose is excreted in the urine when given following 60 days of dosing of 20 grams of colestipol hydrochloride per day.

The increased fecal loss of bile acids due to colestipol hydrochloride administration leads to an increased oxidation of cholesterol to bile acids. This results in an increase in the number of low-density lipoprotein (LDL) receptors, increased hepatic uptake of LDL and a decrease in beta lipoprotein or LDL serum levels, and a decrease in serum cholesterol levels. Although colestipol hydrochloride produces an increase in the hepatic synthesis of cholesterol in man, serum cholesterol levels fall.

There is evidence to show that this fall in cholesterol is secondary to an increased rate of clearance of cholesterol-rich lipoproteins (beta or low-density lipoproteins) from the plasma. Serum triglyceride levels may increase or remain unchanged in colestipol hydrochloride treated patients.

The decline in serum cholesterol levels with colestipol hydrochloride treatment is usually evident by one month. When colestipol hydrochloride is discontinued, serum cholesterol levels usually return to baseline levels within one month. Periodic determinations of serum cholesterol levels as outlined in the National Cholesterol Education Program (NCEP) guidelines, should be done to confirm a favorable initial and long-term response.1

In a large, placebo-controlled, multiclinic study, the LRC-CPPT2 , hypercholesterolemic subjects treated with cholestyramine, a bile-acid sequestrant with a mechanism of action and an effect on serum cholesterol similar to that of colestipol hydrochloride, had reductions in total and LDL-C. Over the 7-year study period the cholestyramine group experienced a 19% reduction (relative to the incidence in the placebo group) in the combined rate of coronary heart disease (CHD) death plus nonfatal myocardial infarction (cumulative incidences of 7% cholestyramine and 8.6% placebo). The subjects included in the study were middle-aged men (aged 35–59) with serum cholesterol levels above 265 mg/dL, LDL-C above 175 mg/dL on a moderate cholesterol-lowering diet, and no history of heart disease. It is not clear to what extent these findings can be extrapolated to other segments of the hypercholesterolemic population not studied.

Treatment with colestipol results in a significant increase in lipoprotein LpAI. Lipoprotein LpAI is one of the two major lipoprotein particles within the high-density lipoprotein (HDL) density range3 , and has been shown in cell culture to promote cholesterol efflux or removal from cells4. Although the significance of this finding has not been established in clinical studies, the elevation of the lipoprotein LpAI particle within the HDL fraction is consistent with an antiatherogenic effect of colestipol hydrochloride, even though little change is observed in HDL cholesterol (HDL-C).

In patients with heterozygous familial hypercholesterolemia who have not obtained an optimal response to colestipol hydrochloride alone in maximal doses, the combination of colestipol hydrochloride and nicotinic acid has been shown to further lower serum cholesterol, triglyceride, and LDL-cholesterol (LDL-C) values. Simultaneously, HDL-C values increased significantly. In many such patients it is possible to normalize serum lipid values.5–7

Preliminary evidence suggests that the cholesterol-lowering effects of lovastatin and the bile acid sequestrant, colestipol hydrochloride, are additive.

The effect of intensive lipid-lowering therapy on coronary atherosclerosis has been assessed by arteriography in hyperlipidemic patients. In these randomized, controlled clinical trials, patients were treated for two to four years by either conventional measures (diet, placebo, or in some cases low-dose resin), or with intensive combination therapy using diet and colestipol hydrochloride granules plus either nicotinic acid or lovastatin. When compared to conventional measures, intensive lipid-lowering combination therapy significantly reduced the frequency of progression and increased the frequency of regression of coronary atherosclerotic lesions in patients with or at risk for coronary artery disease.8–11

Colestipol Hydrochloride Indications and Usage

Since no drug is innocuous, strict attention should be paid to the indications and contraindications, particularly when selecting drugs for chronic long-term use.

Micronized colestipol hydrochloride tablets are indicated as adjunctive therapy to diet for the reduction of elevated serum total and LDL-C in patients with primary hypercholesterolemia (elevated LDL-C) who do not respond adequately to diet. Generally, micronized colestipol hydrochloride tablets have no clinically significant effect on serum triglycerides, but with their use, triglyceride levels may be raised in some patients.

Therapy with lipid-altering agents should be a component of multiple risk factor intervention in those individuals at significantly increased risk for atherosclerotic vascular disease due to hypercholesterolemia. Treatment should begin and continue with dietary therapy (see NCEP guidelines). A minimum of six months of intensive dietary therapy and counseling should be carried out prior to initiation of drug therapy. Shorter periods may be considered in patients with severe elevations of LDL-C or with definite CHD.

According to the NCEP guidelines, the goal of treatment is to lower LDL-C, and LDL-C is to be used to initiate and assess treatment response. Only if LDL-C levels are not available, should the Total-C be used to monitor therapy. The NCEP treatment guidelines are shown below.

LDL-Cholesterol
mg/dL (mmol/L)
Definite Atherosclerotic Disease * Two or More Other Risk Factors Initiation Level Goal
*
Coronary heart disease or peripheral vascular disease (including symptomatic carotid artery disease).
Other risk factors for coronary heart disease (CHD) include: age (males: ≥45 years; female: ≥55 years or premature menopause without estrogen replacement therapy); family history of premature CHD; current cigarette smoking; hypertension; confirmed HDL-C <35 mg/dL (0.91 mmol/L); and diabetes mellitus. Subtract one risk factor if HDL-C is ≥60 mg/dL (1.6 mmol/L).
No No ≥190
(≥4.9)
<160
(<4.1)
No Yes ≥160
(≥4.1)
<130
(<3.4)
Yes Yes or No ≥130
(≥3.4)
≤100
(≤2.6)
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