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Number of Pills Affects Adherence to HIV Treatment Regimens

Patients Taking Combination Pills Three Times More Likely to Refill Prescriptions on Time

RESEARCH TRIANGLE PARK, NC -- November 30, 2005 -- 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 (CombivirŪ) achieved >/= 95% 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.

"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, PharmD, acting vice president, HIV, Infectious Disease Medicine Development Center at GSK.

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.

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% adherent (30/45 = 67%). The threshold for adherence was set at 95%; 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%) compared to patients taking the separate components, lamivudine and zidovudine, (75%) when considering the population subgroup (P <.001). Similarly, in measuring adherence rates for the subpopulation, patients taking Combivir achieved >/= 95% adherence more than twice as often as patients who took the separate components (36% vs. 16% respectively).*

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.

About Combivir
HIV medicines do not cure HIV infection/AIDS or prevent passing HIV to others. Combivir is a combination tablet containing EpivirŪ (lamivudine, 3TC) and RetrovirŪ (zidovudine, AZT). Combivir is indicated in combination with other antiretroviral agents for the treatment of HIV infection. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported.

Zidovudine has been associated with hematologic toxicity including neutropenia and severe anemia, especially in advanced HIV disease, and with symptomatic myopathy after prolonged use. Severe acute exacerbations of hepatitis B have been reported in patients who are co-infected with hepatitis B virus (HBV) and HIV and have discontinued lamivudine, which is one component of Combivir. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue Combivir and are co-infected with HIV and HBV. If appropriate, initiation of antihepatitis B therapy may be warranted. Redistribution/accumulation of body fat has been observed in patients receiving antiretroviral therapy. The causal relationship, mechanism, and long-term consequences of these events are currently unknown. The most frequent adverse events are headache (35%), nausea (33%), malaise/fatigue (27%), and nasal signs and symptoms (20%).

* Data provided by GlaxoSmithKline.


SOURCE GlaxoSmithKline

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