CLINICAL PHARMACOLOGY
A variety of clinical studies have
demonstrated that elevated levels of total cholesterol (TC), low-density
lipoprotein cholesterol (LDL-C), and apolipoprotein B-100 (Apo B) promote human
atherosclerosis. Similarly, decreased levels of high-density lipoprotein
cholesterol (HDL-C) are associated with the development of atherosclerosis.
Epidemiological investigations have established that cardiovascular morbidity
and mortality vary directly with the level of TC and LDL-C, and inversely with
the level of HDL-C.
Cholesterol-enriched triglyceride-rich
lipoproteins, including very low-density lipoproteins (VLDL),
intermediate-density lipoproteins (IDL), and their remnants, can also promote
atherosclerosis. Elevated plasma triglycerides (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 (CHD). As
such, total plasma TG have not consistently been shown to be an independent risk factor for CHD.
As an adjunct to diet, the
efficacy of niacin and lovastatin in improving lipid profiles (either
individually, or in combination with each other, or niacin in combination with
other statins) for the treatment of dyslipidemia has been well documented. The
effect of combined therapy with niacin and lovastatin on cardiovascular
morbidity and mortality has not been determined.
Effects on lipids
ADVICOR
ADVICOR reduces LDL-C, TC, and TG,
and increases HDL-C due to the individual actions of niacin and lovastatin. The
magnitude of individual lipid and lipoprotein responses may be influenced by
the severity and type of underlying lipid abnormality.
Niacin
Niacin functions in the body after conversion to
nicotinamide adenine dinucleotide (NAD) in the NAD coenzyme system. Niacin (but
not nicotinamide) in gram doses reduces LDL-C, Apo B, Lp(a), TG, and TC, and
increases HDL-C. The increase in HDL-C is associated with an increase in apolipoprotein A-I (Apo A-I) and a shift in the distribution of HDL
subfractions. These shifts include an increase in the HDL2:HDL3 ratio, and an
elevation in lipoprotein A-I (Lp A-I, an HDL-C particle containing only Apo
A-I). In addition, preliminary reports suggest that niacin causes favorable LDL
particle size transformations, although the clinical relevance of this effect
is not yet clear.
Lovastatin
Lovastatin has been shown to reduce both normal and elevated
LDL-C concentrations. Apo B also falls substantially during treatment with
lovastatin. Since each LDL-C particle contains one molecule of Apo B, and since
little Apo B is found in other lipoproteins, this strongly suggests that
lovastatin does not merely cause cholesterol to be lost from LDL-C, but also
reduces the concentration of circulating LDL particles. In addition, lovastatin
can produce increases of variable magnitude in HDL-C, and modestly reduces
VLDL-C and plasma TG. The effects of lovastatin on Lp(a), fibrinogen, and
certain other independent biochemical risk markers for coronary heart disease
are not well characterized.
Mechanism of Action
Niacin
The mechanism by which niacin alters lipid profiles is not
completely understood and may involve several actions, including partial
inhibition of release of free fatty acids from adipose tissue, and increased
lipoprotein lipase activity (which may increase the rate of chylomicron
triglyceride removal from plasma). Niacin decreases the rate of hepatic synthesis of VLDL-C and LDL-C, and does not appear to affect fecal excretion of
fats, sterols, or bile acids.
Lovastatin
Lovastatin is a specific inhibitor of
3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the enzyme that
catalyzes the conversion of HMG-CoA to mevalonate. The conversion of HMG-CoA to
mevalonate is an early step in the biosynthetic pathway for cholesterol.
Lovastatin is a prodrug and has little, if any, activity until hydrolyzed to
its active beta-hydroxyacid form, lovastatin acid. The mechanism of the
LDL-lowering effect of lovastatin may involve both reduction of VLDL-C
concentration and induction of the LDL receptor, leading to reduced production
and/or increased catabolism of LDL-C.
Pharmacokinetics
Absorption and Bioavailability
ADVICOR
In single-dose studies of ADVICOR, rate and extent of niacin
and lovastatin absorption were bioequivalent under fed conditions to that from
NIASPAN® (niacin
extended-release tablets) and Mevacor®
(lovastatin) tablets, respectively. After administration of two ADVICOR
1000 mg/20 mg tablets, peak niacin concentrations averaged about 18 mcg/mL and
occurred about 5 hours after dosing; about 72% of the niacin dose was absorbed
according to the urinary excretion data. Peak lovastatin concentrations
averaged about 11 ng/mL and occurred about 2 hours after dosing.
The extent of niacin absorption from ADVICOR was increased
by administration with food. The administration of two ADVICOR 1000 mg/20 mg
tablets under low-fat or high-fat conditions resulted in a 22 to 30% increase
in niacin bioavailability relative to dosing under fasting conditions.
Lovastatin bioavailability is affected by food. Lovastatin Cmax was increased
48% and 21% after a high- and a low-fat meal, respectively, but the lovastatin
AUC was decreased 26% and 24% after a high- and a low-fat meal, respectively,
compared to those under fasting conditions.
A relative bioavailability study results indicated that
ADVICOR tablet strengths (i.e., two tablets of 500 mg/20 mg and one tablet of
1000 mg/40 mg) are not interchangeable.
Niacin
Due to extensive and saturable first-pass metabolism, niacin
concentrations in the general circulation are dose dependent and highly
variable. Peak steady-state niacin concentrations were 0.6, 4.9, and 15.5
mcg/mL after doses of 1000, 1500, and 2000 mg NIASPAN once daily (given as two
500 mg, two 750 mg, and two 1000 mg tablets, respectively).
Lovastatin
Lovastatin appears to be incompletely absorbed after oral
administration. Because of extensive hepatic extraction, the amount of
lovastatin reaching the systemic circulation as active inhibitors after oral
administration is low ( <5%) and shows considerable inter-individual
variation. Peak concentrations of active and total inhibitors occur within 2 to
4 hours after Mevacor® administration.
Lovastatin absorption appears to be increased by at least
30% by grapefruit juice; however, the effect is dependent on the amount of
grapefruit juice consumed and the interval between grapefruit juice and
lovastatin ingestion. With a once-a-day dosing regimen, plasma concentrations
of total inhibitors over a dosing interval achieved a steady-state between the second
and third days of therapy and were about 1.5 times those following a single
dose of Mevacor®.
Although the mechanism is not fully understood, cyclosporine
has been shown to increase the AUC of HMG-CoA reductase inhibitors. The
increase in AUC for lovastatin and lovastatin acid is presumably due, in part,
to inhibition of CYP3A4.
Distribution
Niacin
Niacin is less than 20% bound to human serum proteins and
distributes into milk. Studies using radiolabeled niacin in mice show that
niacin and its metabolites concentrate in the liver, kidney, and adipose
tissue.
Lovastatin
Both lovastatin and its beta-hydroxyacid metabolite are
highly bound ( >95%) to human plasma proteins. Distribution of lovastatin or
its metabolites into human milk is unknown; however, lovastatin distributes
into milk in rats. In animal studies, lovastatin concentrated in the liver, and
crossed the blood-brain and placental barriers.
Metabolism
Niacin
Niacin undergoes rapid and extensive first-pass metabolism
that is dose-rate specific and, at the doses used to treat dyslipidemia,
saturable. In humans, one pathway is through a simple conjugation step with glycine to form nicotinuric acid (NUA). NUA is then excreted, although there
may be a small amount of reversible metabolism back to niacin. The other
pathway results in the formation of NAD. It is unclear whether nicotinamide is
formed as a precursor to, or following the synthesis of, NAD. Nicotinamide is
further metabolized to at least N-methylnicotinamide (MNA) and
nicotinamide-N-oxide (NNO). MNA is further metabolized to two other compounds,
N-methyl-2-pyridone-5-carboxamide (2PY) and N-methyl-4-pyridone5-carboxamide
(4PY). The formation of 2PY appears to predominate over 4PY in humans.
Lovastatin
Lovastatin undergoes extensive first-pass extraction and
metabolism by cytochrome P450 3A4 in the liver, its primary site of action. The
major active metabolites present in human plasma are the beta-hydroxyacid of
lovastatin (lovastatin acid), its 6'-hydroxy derivative, and two additional
metabolites.
Elimination
ADVICOR
Niacin is primarily excreted in urine mainly as metabolites.
After a single dose of ADVICOR, at least 60% of the niacin dose was recovered
in urine as unchanged niacin and its metabolites. The plasma half-life for
lovastatin was about 4.5 hours in single-dose studies.
Niacin
The plasma half-life for niacin is about 20 to 48 minutes
after oral administration and dependent on dose administered. Following
multiple oral doses of NIASPAN, up to 12% of the dose was recovered in urine as
unchanged niacin depending on dose administered. The ratio of metabolites
recovered in the urine was also dependent on the dose administered.
Lovastatin
Lovastatin is excreted in urine and bile, based on studies
of Mevacor®. Following an
oral dose of radiolabeled lovastatin in man, 10% of the dose was excreted in
urine and 83% in feces. The latter represents absorbed drug equivalents
excreted in bile, as well as any unabsorbed drug.
Special Populations
Hepatic
No pharmacokinetic studies have been conducted in patients
with hepatic insufficiency for either niacin or lovastatin (see WARNINGS, Liver
Dysfunction).
Renal
No information is available on the pharmacokinetics of
niacin in patients with renal insufficiency.
In a study of patients with severe renal insufficiency
(creatinine clearance 10 to 30 mL/min), the plasma concentrations of total
inhibitors after a single dose of lovastatin were approximately two-fold higher
than those in healthy volunteers.
ADVICOR should be used with caution in patients with renal
disease.
Gender
Plasma concentrations of niacin and metabolites after
single- or multiple-dose administration of niacin are generally higher in women
than in men, with the magnitude of the difference varying with dose and
metabolite. Recovery of niacin and metabolites in urine, however, is generally
similar for men and women, indicating similar absorption for both genders. The
gender differences observed in plasma niacin and metabolite levels may be due
to gender-specific differences in metabolic rate or volume of distribution.
Data from clinical trials suggest that women have a greater hypolipidemic
response than men at equivalent doses of NIASPAN and ADVICOR.
In a multiple-dose study, plasma concentrations of active
and total HMG-CoA reductase inhibitors were 20 to 50% higher in women than in
men. In two single-dose studies with ADVICOR, lovastatin concentrations were
about 30% higher in women than men, and total HMG-CoA reductase inhibitor
concentrations were about 20 to 25% greater in women.
In a multi-center, randomized, double-blind,
active-comparator study in patients with Type IIa and IIb hyperlipidemia,
ADVICOR was compared to single-agent treatment (NIASPAN and lovastatin). The
treatment effects of ADVICOR compared to lovastatin and NIASPAN differed for
males and females with a significantly larger treatment effect seen for
females. The mean percent change from baseline at endpoint for LDL-C, TG, and
HDL-C by gender are as follows (Table 1):
Table 1: Mean percent change from baseline at endpoint
for LDL-C, HDL-C and TG by gender
|
ADVICOR 2000 mg/40 mg |
NIASPAN 2000 mg |
Lovastatin 40 mg |
Women
(n=22) |
Men
(n=30) |
Women
(n=28) |
Men
(n=28) |
Women
(n=21) |
Men
(n=38) |
LDL-C |
-47% |
-34% |
-12% |
-9% |
-31% |
-31% |
HDL-C |
33% |
24% |
22% |
15% |
3% |
7% |
TG |
-48% |
-35% |
-25% |
-15% |
-15% |
-23% |
Drug-drug Interactions
Table 2: The Effects of Other
Drugs on Lovastatin Exposure When Both Were Co-administered
Drug |
N |
Dose of Co-administered Drug or Grapefruit Juice |
Dosing of Lovastatin |
AUC Ratio* (with / without coadministered drug)
No Effect = 1.00 |
Lovastatin |
Lovastatin Acid† |
Gemfibrozil |
11 |
600 mg BID for 3 days |
40 mg |
0.96 |
2.8 |
Itraconazole‡ |
12 |
200 mg QD for 4 days |
40 mg on Day 4 |
> 36§ |
22 |
10 |
100 mg QD for 4 days |
40 mg on Day 4 |
> 14.8§ |
15.4 |
Grapefruit Juice¶ (high dose) |
10 |
200 mL of double-strength TID# |
80 mg single dose |
15.3 |
5 |
Grapefruit Juice¶ (low dose) |
16 |
8 oz (about 250 mL) of single-strengthÞ for 4 days |
40 mg single dose |
1.94 |
1.57 |
Cyclosporine |
16 |
Not describedβ |
10 mg QD for 10 days |
5- to 8-fold |
NDa |
|
Number of Subjects |
Dosing of Coadministered Drug or Grapefruit Juice |
Dosing of Lovastatin |
AUC Ratio* (with / without coadministered drug) No Effect = 1.00 |
Total Lovastatin Acid e |
Diltiazem |
10 |
120 mg BID for 14 days |
20 mg |
3.57e |
* Results based on a chemical
assay.
† Lovastatin acid refers to the β-hydroxyacid of lovastatin.
‡ The mean total AUC of lovastatin without itraconazole phase could not be
determined accurately. Results could be representative of strong CYP3A4
inhibitors such as ketoconazole, posaconazole, clarithromycin, telithromycin, HIV protease inhibitors, and nefazodone.
§ Estimated minimum change.
¶The effect of amounts of
grapefruit juice between those used in these two studies on lovastatin
pharmacokinetics has not been studied.
# Double-strength: one can of frozen concentrate diluted with one can of
water. Grapefruit juice was administered TID for 2 days, and 200 mL together
with single dose lovastatin and 30 and 90 minutes following single dose
lovastatin on Day 3.
Þ Single-strength: one
can of frozen concentrate diluted with 3 cans of water. Grapefruit juice was
administered with breakfast for 3 days, and lovastatin was administered in the
evening on Day 3.
β Cyclosporine-treated
patients with psoriasis or post kidney or heart transplant patients with stable
graft function, transplanted at least 9 months prior to study.
aND = Analyte not determined.
eLactone converted to acid by hydrolysis prior to analysis. Figure represents total unmetabolized acid and lactone. |
Clinical Studies
In a multi-center, randomized, double-blind, parallel,
28-week, active-comparator study in patients with Type IIa and IIb
hyperlipidemia, ADVICOR was compared to each of its components (NIASPAN and
lovastatin). Using a forced dose-escalation study design, patients received
each dose for at least 4 weeks. Patients randomized to treatment with ADVICOR
initially received 500 mg/20 mg. The dose was increased at 4-week intervals to
a maximum of 1000 mg/20 mg in one-half of the patients and 2000 mg/40 mg in the
other half. The NIASPAN monotherapy group underwent a similar titration from
500 mg to 2000 mg. The patients randomized to lovastatin monotherapy received
20 mg for 12 weeks titrated to 40 mg for up to 16 weeks. Up to a third of the
patients randomized to ADVICOR or NIASPAN discontinued prior to Week 28. In
this study, ADVICOR decreased LDL-C, TG and Lp(a), and increased HDL-C in a
dose-dependent fashion (3, 4, 5 and 6 below). Results from this study for LDL-C
mean percent change from baseline (the primary efficacy variable) showed that:
- LDL-lowering with ADVICOR was significantly greater than
that achieved with lovastatin 40 mg only after 28 weeks of titration to a dose
of 2000 mg/40 mg (p <.0001)
- ADVICOR at doses of 1000 mg/20 mg or higher achieved greater
LDL-lowering than NIASPAN (p <.0001) The LDL-C results are summarized in
Table 3.
Table 3: LDL-C mean percent change from baseline
Week |
ADVICOR |
NIASPAN |
Lovastatin |
n* |
Dose (mg/mg) |
LDL |
n* |
Dose (mg) |
LDL |
n* |
Dose (mg) |
LDL |
Baseline |
57 |
- |
190.9 mg/dL |
61 |
- |
-189.7 mg/dL |
61 |
- |
185.6 mg/dL |
12 |
47 |
1000/20 |
-30% |
46 |
1000 |
-3% |
56 |
20 |
-29% |
16 |
45 |
1000/40 |
-36% |
44 |
1000 |
-6% |
56 |
40 |
-31% |
20 |
42 |
1500/40 |
-37% |
43 |
1500 |
-12% |
54 |
40 |
-34% |
28 |
42 |
2000/40 |
-42% |
41 |
2000 |
-14% |
53 |
40 |
-32% |
*n = number of patients remaining
in the trial at each timepoint |
ADVICOR achieved significantly
greater HDL-raising compared to lovastatin and NIASPAN monotherapy at all doses
(Table 4).
Table 4: HDL-C mean percent change from baseline
Week |
ADVICOR |
NIASPAN |
Lovastatin |
n* |
Dose (mg/mg) |
HDL |
n* |
Dose (mg) |
HDL |
n* |
Dose (mg) |
HDL |
Baseline |
57 |
- |
45 mg/dL |
61 |
- |
47 mg/dL |
61 |
- |
43 mg/dL |
12 |
47 |
1000/20 |
20% |
46 |
1000 |
+14% |
56 |
20 |
+3% |
16 |
45 |
1000/40 |
20% |
44 |
1000 |
+15% |
56 |
40 |
+5% |
20 |
42 |
1500/40 |
27% |
43 |
1500 |
+22% |
54 |
40 |
+6% |
28 |
42 |
2000/40 |
30% |
41 |
2000 |
+24% |
53 |
40 |
+6% |
*n = number of patients remaining
in the trial at each timepoint |
In addition, ADVICOR achieved
significantly greater TG-lowering at doses of 1000 mg/20 mg or greater compared
to lovastatin and NIASPAN monotherapy (Table 5).
Table 5: TG median percent
change from baseline
Week |
ADVICOR |
NIASPAN |
Lovastatin |
n* |
Dose (mg/mg) |
TG |
n* |
Dose (mg) |
TG |
n* |
Dose (mg) |
TG |
Baseline |
57 |
- |
174 mg/dL |
61 |
- |
186 mg/dL |
61 |
- |
171 mg/dL |
12 |
47 |
1000/20 |
-32% |
46 |
1000 |
-22% |
56 |
20 |
-20% |
16 |
45 |
1000/40 |
-39% |
44 |
1000 |
-23% |
56 |
40 |
-17% |
20 |
42 |
1500/40 |
-44% |
43 |
1500 |
-31% |
54 |
40 |
-21% |
28 |
42 |
2000/40 |
-44% |
41 |
2000 |
-31% |
53 |
40 |
-20% |
*n = number of patients remaining
in the trial at each timepoint |
The Lp(a) lowering effects of
ADVICOR and NIASPAN were similar, and both were superior to lovastatin (Table
6). The independent effect of lowering Lp(a) with NIASPAN or ADVICOR on the
risk of coronary and cardiovascular morbidity and mortality has not been
determined.
Table 6: Lp(a) median percent
change from baseline
Week |
ADVICOR |
NIASPAN |
Lovastatin |
n* |
Dose (mg/mg) |
Lp(a) |
n* |
Dose (mg) |
Lp(a) |
n* |
Dose (mg) |
Lp(a) |
Baseline |
57 |
- |
34 mg/dL |
61 |
- |
41 mg/dL |
60 |
- |
42 mg/dL |
12 |
47 |
1000/20 |
-9% |
46 |
1000 |
-8% |
55 |
20 |
+8% |
16 |
45 |
1000/40 |
-9% |
44 |
1000 |
-12% |
55 |
40 |
+8% |
20 |
42 |
1500/40 |
-17% |
43 |
1500 |
-22% |
53 |
40 |
+6% |
28 |
42 |
2000/40 |
-22% |
41 |
2000 |
-32% |
52 |
40 |
0% |
*n = number of patients remaining
in the trial at each timepoint |
ADVICOR Long-Term Study
A total of 814 patients were
enrolled in a long-term (52-week), open-label, single-arm study of ADVICOR.
Patients were force dose-titrated to 2000 mg/40 mg over 16 weeks. After
titration, patients were maintained on the maximum tolerated dose of ADVICOR
for a total of 52 weeks. Five hundred-fifty (550) patients (68%) completed the
study, and fifty-six percent (56%) of all patients were able to maintain a dose
of 2000 mg/40 mg for the 52 weeks of treatment. The lipid-altering effects of
ADVICOR peaked after 4 weeks on the maximum tolerated dose, and were maintained
for the duration of treatment. These effects were comparable to what was
observed in the double-blind study of ADVICOR (Tables 3-5).