Patients Taking Fixed-dose Combination Pills Are More Likely to Refill Prescriptions
on Time
Fixed-dose
combination therapies for HIV may
increase the likelihood of treatment adherence
among patients, according to a recently published study of 2,112 patients conducted
by GlaxoSmithKline. Patients taking a fixed-dose combination of lamivudine
(3TC) 150 mg and zidovudine
(ZDV) 300 mg (COMBIVIR®) achieved ≥ 95 percent adherence more
than twice as often as patients whose regimens included 3TC and ZDV as separate
pills.
The
results were published in the November issue of AIDS Care. The retrospective,
longitudinal cohort study analyzed 60-day prescription refill Medicaid claims
data from 1995-2001. The data combined to cover more than 3.3 million patient
lives.
“Pill
burden is an important factor in achieving desirable adherence rates. Fixed-dose
combination products have been available for almost a decade, with COMBIVIR being
the first to market. However, until now, limited data have existed demonstrating
the ability of these products to facilitate adherence. That’s why we are encouraged
by the results of this study,” said Mark Shaefer, Pharm. D., acting vice president,
HIV, Infectious Disease Medicine Development Center at GSK. Following are excerpts
from the text of an announcement from GlaxoSmithKline about the survey results.
Survey Findings
HIV positive patients taking COMBIVIR achieved
a ≥ 95 percent adherence rate more than twice as often as patients taking
lamivudine and zidovudine separately.
Mean adherence
was higher for patients taking COMBIVIR (85 percent) compared to patients taking
the separate components, lamivudine and zidovudine, (75 percent) when considering
the population subgroup (1997-2000) (p<0.001).
To adjust for the time prior to the approval of a fixed-dose
combination therapy (COMBIVIR) in 1997, two sets of adjusted analysis were conducted,
one for the total population (n=2,112) over the entire study period (1995-2001)
and another for the population subgroup (n=1,427) that received separate pills
or combination therapy from September 1997 to December 2000.
The investigators focused on the results for the subgroup
analysis to minimize the potential influence of other time-related variables on
the outcome. The primary study outcome was medication adherence as assessed by
prescription refill data. The adherence ratio was calculated for each prescription
during the follow up period; for example, a patient with a prescription claim
for a 30-day supply who did not refill the prescription until 45 days later would
be considered 67 percent adherent (30/45 = 67 percent).
The threshold for adherence was set at 95 percent; existing
evidence suggests that this level of adherence is associated with a lower risk
of virologic failure. A patient would have been considered non-adherent on or
after the 32nd day following a 30-day prescription refill.
Mean adherence was higher for patients taking COMBIVIR
(85 percent) compared to patients taking the separate components, lamivudine and
zidovudine, (75 percent) when considering the population subgroup (p<0.001).
Similarly, in measuring adherence rates for the subpopulation, patients taking
COMBIVIR achieved ≥ 95 percent adherence more than twice as often as patients
who took the separate components (36 percent vs. 16 percent respectively). [Data
provided by GlaxoSmithKline].
Researchers also reported that findings from analyses
conducted with the entire population during the complete study period (1995-2001)
were similar to those found in the subgroup analysis.
“Fixed-dose combinations like COMBIVIR can reduce treatment
complexity when compared to their separate components. Treatment complexity is
a common barrier to adherence and fixed-dose combination products should be considered
for patients with difficulty adhering to their medication regimen,” said Shaefer.
COMBIVIR
was the first two-drug combination tablet approved for HIV treatment and is one
of the most studied and widely prescribed dual nucleoside combination products.
One out of five people currently taking antiretrovirals in the United States
is prescribed COMBIVIR.
12/02/05
Source
GlaxoSmithKline.
NUMBER OF PILLS AFFECTS ADHERENCE TO HIV TREATMENT REGIMENS. Press Release.
November 30, 2005.
