Modern HIV treatment can work well with adherence below 95%

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Dear Forum Members,

 

Patients taking modern antiretroviral regimens still have a good chance of

maintaining an undetectable viral load if their adherence is below 95%, Spanish

researchers report in the October edition of AIDS Research and Human

Retroviruses. They found that patients taking HIV treatment based on either a

non-nucleoside reverse transcriptase inhibitor (NNRTI) or a ritonavir-boosted

protease inhibitor at an adherence rate of only 80% was associated with a risk

of virological failure below 10%.

This is the equivalent of missing no more than one dose in five of a once-daily

combination. Ninety per cent adherence is the equivalent of missing one dose in

ten - a substantial difference in the frequency of missed doses.

But the study’s authors emphasise that the goal should still be to achieve the

highest possible rate of treatment adherence as there were very low rates of

treatment failure even amongst patients whose level of adherence was at least

90%.

Antiretroviral therapy provides HIV-positive individuals with the chance of

living a long and healthy life. However, HIV treatment is a life-long commitment

and can involve side-effects. Furthermore, many patients find it difficult to

sustain high levels of adherence to their antiretroviral therapy, and poor

treatment adherence is associated with the emergence of drug-resistant HIV as

well as an increased risk of HIV-related illness and death.

It is generally said that it is necessary to take at least 95% of HIV treatment

doses at the right time and in the right way for antiretroviral therapy to have

the best chance of achieving and maintaining suppression of HIV.

However, this estimate was based upon outcomes seen in patients taking older

unboosted protease inhibitors, a class of drugs that is no longer recommended.

Therefore researchers in Barcelona studied the level of adherence needed to

maintain an undetectable viral load in patients taking antiretroviral therapy

based upon NNRTIs or boosted protease inhibitors.

Their research involved 1142 treatment-naïve and treatment-experienced patients

who were prescribed antiretroviral therapy between 2004 and 2005. All the

patients had achieved an undetectable viral load. The study lasted one year.

These patients were divided according to the type of antiretroviral regimen they

were taking: unboosted protease inhibitor (11%); boosted protease inhibitor

(31%); and NNRTI (58%). Adherence was assessed by pill count during routine

clinic appointments. The researchers compared the risk of viral load increasing

to detectable for each of the drug classes at various levels of adherence: below

70%; 70-80%; 80-90% and above 90%. They also examined whether any treatment or

patient characteristics were associated with adherence and outcome.

Most of the patients (1059) maintained an undetectable viral load for the

duration of the study, and their mean level of adherence was 96%. Mean adherence

for the 83 individuals who experienced a breakthrough in their viral load was

76%.

Compared to patients with 90% adherence or better, the risk of virologic failure

was 9% for those with adherence between 80-90%, increasing to 46% of those with

adherence between 70-80% and 77% for those who took below 70% of their doses.

At all levels of adherence below 90%, those taking an unboosted protease

inhibitor were the group most likely to develop resistance (100% failure rate

for adherence below 70%, 71%failure rate for adherence between 70-79%, 24%

failure rate for adherence between 80-89%).

Although the failure rate for patients taking a boosted protease inhibitor and

adherence below 90% was higher for patients taking a boosted protease inhibitor

than those taking an NNRTI, it was not significantly so (below 70%, 50% vs. 35%;

between 70-79%, 37% vs. 24%, between 80-89%, 9% vs. 6%).

The only factors associated with adherence were the number of pills (with the

chances of adherence decreasing significantly as the number of pills increased,

p < 0.001), and number of daily doses. However, although adherence was poorer

amongst patients taking their treatment three times a day, there were no

significant differences between patients taking their treatment once-daily and

twice-daily.

Our data show that virologic success is possible with less than 95%

adherenceâ€, conclude the investigators, adding, “for patients taking NNRTI-

or boosted protease inhibitor-based regimens with adherence rates of 80%, the

failure rate is less than 10%.

However, the investigators found extremely low rates of treatment failure for

patients with adherence above 90% (1% for those taking an unboosted protease

inhibitor, 0.5% for those taking a boosted protease inhibitor and 1.4% for those

taking an NNRTI) and therefore conclude, that the goal should still be to

achieve “the highest rate of adherence possible.â€

Reference

Marin M. Relationship between adherence level, type of antiretroviral regimen,

and plasma HIV type 1 RNA viral load: a prospective cohort study. AIDS Research

and Human Retroviruses 24: 1263-68, 2008.

Dr Diwakar Tejaswi

MBBS(Gold Medalist); MCH; FCCP; Ph.D.

Family Physician and Medical Director

Regional AIDS Training Centre and Network in India(RATNEI)

International Health Organization

India Office: B-33, Indirapuri Colony, Patna 800014, India

Phone: +91-612-3299323 (O); 2586788 (Telefax O); Clinic- Telefax:

+91-612-2206964; Mobile: +91-9835078298; Res: +91-612-2351771

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