Antiretroviral therapy adherence and drug–drug
It is estimated that by 2015 more than half of all HIV-infected individuals in the UnitedStates will be 50 years of age or older. As this population ages, the frequency of non-AIDS related comorbidities increases, which includes cardiovascular, metabolic,gastrointestinal, genitourinary and psychiatric disorders. As a result, medical manage-ment of the aging HIV population can be complicated by polypharmacy and higher pillburden, leading to poorer antiretroviral therapy (ART) adherence. Adherence to ART isgenerally better in older populations when compared to younger populations; however,cognitive impairment in elderly patients can impair adherence, leading to worsetreatment outcomes. Practical monitoring tools can improve adherence and increaserates of viral load suppression. Several antiretroviral drugs exhibit inhibitory and/orinducing effects on cytochrome P450 isoenzymes, which are responsible for themetabolism of many medications used for the treatment of comorbidities in the agingHIV population. The combination of ART with polypharmacy significantly increases thechance of potentially serious drug–drug interactions (DDIs), which can lead to drugtoxicity, poorer ART adherence, loss of efficacy of the coadministered medication, orvirologic breakthrough. Increasing clinicians awareness of common DDIs and the use ofDDI programs can prevent coadministration of potentially harmful combinations inelderly HIV-infected individuals. Well designed ART adherence interventions and DDIstudies are needed in the elderly HIV population.
ß 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Keywords: adherence, aging, antiretroviral therapy, drug–drug interactions
shifts from AIDS-related opportunistic infections to age-related comorbidities, such as cardiovascular disease,
The introduction of effective antiretroviral therapy
(ART) has resulted in the reduction of AIDS-related
osteoporosis and decline in organ function (renal as well
mortality and increased the life expectancy of HIV-
as hepatic) When controlling for sex, baseline CD4
infected individuals By 2015, it is projected that more
cell count and year of therapy initiation, older age (50
than 50% of all HIV-infected individuals living in the
years of age and older) was significantly associated with
United States will be 50 years of age or older With
higher mortality [adjusted hazard ratio 1.23, 95%
increasing age, the pattern of morbidity and mortality
confidence interval (CI) 1.08–1.42] In addition,
aDepartment of International Health, bDepartment of Epidemiology, Johns Hopkins Bloomberg School of Public Health,Baltimore, Maryland, USA, cDepartment of Medicine and Centre for Infectious Diseases, Stellenbosch University, Faculty ofHealth Sciences Cape Town, Cape Town, South Africa, dDepartment of Pharmacy, The Johns Hopkins Hospital, Baltimore,Maryland, USA, eDepartment of Primary Care Sciences, Faculty of Health Sciences, Keele University, Keele, Staffordshire, UK,
fUniversite´ catholique de Louvain, Louvain Drug Research Institute, Brussels, and CHU Mont-Godinne, Yvoir, Belgium, and
gDivision of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland,USA. Correspondence to Jean B. Nachega, MD, PhD, Global Disease Epidemiology and Control Program, Department of InternationalHealth, Bloomberg School of Public Health, Johns Hopkins University, 615N Wolfe Street, Suite W5031, Baltimore, MD 21205,USA. Tel: +1 410 955 2378; fax: +1 410 502 6733; e-mail: Received: 12 December 2011; accepted: 23 April 2012.
ISSN 0269-9370 Q 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Goulet et al. reported that HIV-infected veterans had a
were not confirmed by Tumbarello et al. Among
lower risk of hypertension, diabetes, vascular disease and
other factors, biological factors that negatively influence
psychiatric disorders. However, they had a higher risk of
the risk of developing immune responses and immune
liver disease, renal disease, substance use disorder and
reconstitution (e.g. advanced diseases at start of ART,
multimorbidity. HIV infected veterans 50 years of age and
thymic output, reduced bone marrow capacity) may
older had higher odds of multimorbidity than HIV
affect outcome in the older HIV-infected patients
uninfected veterans 50 years of age and older.
Due to the above comorbidities, medical management ofolder HIV-infected individuals becomes complicated bypolypharmacy. In an analysis of the Swiss HIV Cohortstudy, the combination of ART with polypharmacy
significantly increased the chance of potentially serious
drug–drug interactions (DDIs) which can lead todrug toxicity, loss of efficacy of the coadministered
Overall, higher adherence to ART is associated with older
medication and virologic breakthrough. When HIV-
age, and although current combination ART can be
infected individuals at least 50 years of age were compared
forgiving of occasional lapses in adherence, higher levels
to HIV-infected individuals less than 50 years of age, older
of adherence is associated with the maximal likelihood of
patients were more likely to receive concomitant
virologic suppression and lower level of drug resistance
medications versus younger patients (82 vs. 61%,
in both younger adults and older patients
P < 0.001), therefore, also had more DDIs (51 vs. 35%,
However, among older patients with HIV, those with
P < 0.001). Certain therapeutic classes were prescribed
documented cognitive decline are likely to have poor
more often in elderly patients, including cardiovascular
ART adherence, disease progression and death In a
drugs, gastrointestinal medications and hormonal agents.
volunteer sample of 431 HIV-infected adult patients on
Elderly patients are two to three times more likely to
ART, recruited from community agencies and university-
develop an adverse drug reaction compared to younger
affiliated infectious disease clinics in the Los Angeles area,
patients There is a paucity of clinical and
neurocognitive measurements were conducted. These
pharmacokinetic DDI studies in the older HIV popu-
included tests on attention, information processing speed,
lation. In a cohort study of 1000 HIV-negative elderly
learning/memory, verbal fluency, motor functioning and
patients more than 70 years old who were admitted to
the hospital for an acute illness, 894 were receiving at
measured using microchip-embedded pill bottle caps
least two medications. Of these 894 patients, 60.2%
(Medication Event Monitoring System caps) and was self-
were exposed to potential DDI, and as a result of these
reported. Structural equation modeling (SEM) tech-
DDI, 24% developed clinically significant side effects
niques were used to evaluate factor models of cognition
and adherence. The study found that mean adherencerates were higher among older (50 years) than younger
Other important ART considerations in the aging HIV
(<50 years) HIV-positive adults. Nevertheless, the SEM
population include issues related to adherence, as well as
analysis revealed that older patients with neurocognitive
clinical/immunological response to ART. Poor adher-
impairment were associated with poorer medication
ence to ART in the aging HIV population can be the
consequence of multiple factors including neurocognitive
examined individually, executive function, motor func-
decline social isolation/lack of social support
tion and processing speed were most strongly correlated
and depression and chronic adverse drug effects
with adherence in this elderly group. Similar to younger
(e.g. lipodystrophy) High drug cost in uninsured or
patients, older HIV-positive individuals with neuro-
underinsured elderly patients is also associated with
cognitive impairment or drug abuse problems are at
decreased adherence and poor outcome As an
increased risk of suboptimal adherence to medica-
example, in the North American AIDS Cohort
tions.The above findings highlight the importance of
Collaboration on Research and Design cohort, it was
optimizing medication adherence rates and evaluating
found that older age (per 10 years increment) was
neurocognition in the growing population of elderly
associated with a 68% increase in death when ART was
deferred and that CD4 cell count at presentationfor HIV care among patients older than 50 years old were
In 2008, Branas et al. also found that older age was
lower Although elderly patients may have a higher
associated with higher ART adherence, however, the
baseline HIV viral load and lower CD4 cell count, their
authors did not investigate neurocognition disorders as
virologic response to ART is similar to younger HIV-
independent factors. In addition, they found a lower
infected individuals but CD4 cell recovery after
CD4 cell count increase after ART initiation in the
starting ART is generally lower in this elderly HIV-
older group. Hinkin et al. found that in addition
infected population However, these findings
to neurocognition disorders, current drug abuse or
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Antiretrovirals in the aging HIV population Nachega et al.
dependence, but not current alcohol abuse or depen-
between older and younger HIV-infected patients
dence, was also associated with suboptimal medication
regarding viroimmunological response to ART.
Antiretroviral drug–drug interactions in
interventions in the aging HIV population
The combination of ART with polypharmacy for the
There are limited interventional studies aimed to improve
management of comorbidities significantly increases the
ARTadherence in the elderly HIV population to guide or
chance of potentially serious DDI, which can lead to drug
support specific recommendations. Although one could
toxicity and loss of efficacy. The effect of aging on drug
extrapolate from other interventions conducted in elderly
metabolism and clearance adds another layer of complex-
patients affected by chronic conditions such as diabetes or
ity. Liver volume and hepatic blood flow decrease with increasing age. Comparisons of drug
hypertension, it is important to evaluate such interven-
metabolism in vivo have been conducted in younger
tions in the aging HIV population and more specifically
versus older HIV-negative patients. CYP1A2 activity
those with neurocognition disorders and/or drug abuse.
seems to be preserved in older patients, particularly those
ART adherence interventions that have proven effective
who are nonsmokers Age does not seem to affect
in the adult HIV-infected population includes electronicreminder devices screening for and treating
CYP2D6 metabolism, whereas CYP2D6 polymorphisms
depression addressing substance abuse organiz-
were found to significantly impact elimination
ing pillboxes increasing social support and
The following age-related differences in CYP2C19
simplifying ART regimens by reducing pill burden and
metabolism have been noted; older individuals who are
frequency (e.g. once-daily and one tablet fixed-dose
either extensive metabolizers or intermediate metaboli-
combinations) These interventions are likely to be of
zers have approximately two-fold higher exposures toomeprazole compared to younger individuals. However,
value in the elderly HIV population, but specific data in
age had less effect on poor metabolizers Age does
this aging population are urgently needed.
not appear to affect CYP2C9 metabolism of diclofenacand celecoxib however, warfarin is primarilymetabolized through CYP2C9, and it has been shown
that the average dose requirement for warfarin decreases
as age increases Lastly, age has not been shown to
significantly influence CYP3A metabolism even inpatients up to 100 years old This is important
HIV-infected patients over the age of 50 are more likely
because CYP3A enzymes are involved in the metabolism
to present with lower CD4 cell counts and more
of a majority of medications, and are the basis of many
advanced disease As a result, among patients who are
clinically important DDIs between ART and medications
older than 60 years of age, a higher proportion of these
commonly prescribed in the aging population. These
patients progressed to AIDS within 1 year of HIV
studies suggest that the overall hepatic elimination through
diagnosis compared to younger patients (52 vs. 15%)
CYP450 enzymes is relatively stable with increasing age. Similarly, phase II metabolism (glucuronidation, acety-
Although older HIV-infected individuals are less likely to
lation, and sulfatation) is also well preserved in older
experience treatment failure with ART compared to
patients . Enzyme induction also appears to be
younger patients due to better adherence, some studies
conserved in older patients, as rifampin was capable of
suggest that older individuals have less CD4 cell recovery
inducing phase I and phase II pathways of metabolism to
In a Spanish study, Nogueras et al. showed
the same extent as in younger individuals
that although HIV-infected older patients were morelikely to have higher viral load and lower CD4 cell counts
On average, glomerular filtration declines by 1% per
at baseline when presenting to the first clinic visit, they
year . HIV-infected patients are at increased risk for
were not likely to achieve the same CD4 cell counts
developing chronic kidney disease (CKD) with a
compared with younger individuals. Based on these
prevalence of an estimated glomerular filtration rate less
observations, the Department of Health and Human
than 60 ml/min per 1.73 m2 reported in approximately 7%
Services guidelines recommended ART in all patients
of HIV-infected patients . In addition to older age,
older than 50 years of age, regardless of CD4 cell count
many other factors such as diabetes, hypertension,
However, as shown by Tumbarello et al. despite
intravenous drug use, high viral load, low CD4 cell count,
having lower baseline CD4 cell count and higher
race, concurrent use of certain antiretrovirals [e.g. teno-
frequency of comorbid conditions, in multivariate
fovir, indinavir, atazanavir (ATV)] and hepatitis C coinfec-
analysis, there was no statistically significant difference
tion have been associated with CKD in HIV-infected
Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
individuals In a large cohort study from the
long-term ART and potentially due to HIV immune
Veteran Health Administration involving over 10 000
activation. Prolonged treatment with ART is associated
HIV-infected patients, tenofovir use was associated with a
with a higher prevalence of hypertension in HIV-infected
34% increased risk of proteinuria (95% CI 25–45%,
individuals Routine blood pressure monitoring and
P < 0.0001), 11% increased risk of rapid decline in kidney
initiation of antihypertensive medications when indicated
function (95% CI 3–18%, P ¼ 0.0033), and 33% increased
is essential to decrease the risk of developing hyperten-
risk of CKD (95% CI 18–51%; P < 0.0001). Risk of
sion-related morbidities DDI studies involving
tenofovir-associated nephrotoxicity did not further
cardiovascular agents and antiretroviral drugs were
increase in a subgroup of patients older than 46 years
conducted in young healthy volunteers. All dihydropyr-
However, in an expanded-access tenofovir study,
idine calcium channel blockers (CCBs) are metabolized
older age was a baseline risk factor for increased serum
via CYP3A4; as a result, all boosted protease inhibitors
creatinine . It is important for clinicians to recognize
may increase CCB serum concentrations and can
that older HIV-infected patients may have decreased
potentially prolong the PR interval and augment
glomerular filtration rate, and as a result may be at higher
hypotensive effect. In a drug interaction study conducted
risk of nucleoside/nucleotide reverse transcriptase inhibi-
with unboosted ATV, diltiazem area under the plasma
tor (NRTI)-induced toxicity if renal dosing guidelines are
concentration time curve (AUC) was increased by 225%
and the PR interval was prolonged although the majorityof patients were asymptomatic with first degree
Clinically significant DDI involving ART and medi-
atrioventricular block Therefore, it is recommended
cations used to treat cardiovascular diseases, metabolic,
to decrease the diltiazem dose by 50% and titrate slowly
gastrointestinal, psychiatric disorders and other medi-
with close monitoring Similarly, use of other CCB
cations commonly used in the elderly population are
that are more likely to prolong the PR interval (e.g.
reviewed here with recommendations provided for the
verapamil) with boosted protease inhibitors should be
selection of alternative agents to minimize potentially
closely monitored. On the contrary, EFV, ETR and NVP
harmful DDI. As a class effect, protease inhibitors are
have the potential to decrease CCB serum concentrations
inhibitors of CYP450 3A4 enzymes and to some extent of
and dose adjustment of CCB at steady state may be
other isoenzymes, with the most potent being ritonavir
needed. Digoxin serum concentrations were increased by
(RTV), which is used to ‘boost’ the effect of other
86% with RTV coadministration due to inhibition of P-
protease inhibitors by inhibiting their metabolism. Inter-
glycoprotein (P-gp). In a cohort study involving
actions between protease inhibitors and other medications
2030 HIV-negative elderly patients who were taking
metabolized through CYP450 may lead to increased
digoxin, if they had been hospitalized during the previous
plasma concentrations of the coadministered medication,
2 months, they were at more than four times increased
potentially leading to serious/life-threatening adverse
risk for additional hospitalizations due to digoxin toxicity
drug reactions. With the exception of delavirdine (DLV)
With the increased risk of CKD and potential for
and rilpivirine, nonnucleoside reverse transcriptase
DDI with boosted protease inhibitors, HIV-infected
inhibitors (NNRTIs) including efavirenz (EFV), etra-
elderly patients may be at even higher risk for digoxin
virine (ETR) and nevirapine (NVP) are moderate
toxicity. Close monitoring of digoxin serum concen-
inducers in vivo of CYP450 3A4 enzymes, although
trations is critical in older HIV-infected patients.
EFV has been found in vitro to inhibit certain CYP450enzymes as well . Interactions involving EFV, NVP
Many antiarrhythmic medications are CYP450 3A4
and ETR and other medications metabolized through
substrates. The use of amiodarone, bepridil, flecainide,
CYP450 3A4 can lead to decreased plasma con-
propafenone and quinidine are contraindicated with
centrations of the coadministered medication, poten-
RTV boosted protease inhibitors (PI/r) due to the
tially leading to decreased efficacy. NRTIs, maraviroc,
potential risk of exacerbating cardiac arrhythmias
raltegravir, rilpivirine and enfuvirtide do not inhibit or
The use of disopyramide, dofetilide, lidocaine, mexiletine
induce CYP450 isoenzymes; therefore, clinically sig-
and procainamide with PI/r should be approached with
caution due to the potential risk of significantly increasingantiarrhythmic serum concentrations.
Drug–drug interactions withcardiovascular medications
Drug–drug interactions withanticoagulation
Cardiovascular disease is one of the most commoncomorbidities in the aging HIV-infected population
Older age is associated with increased risk of major
Coronary artery disease (CAD) is emerging as a
hemorrhage when taking warfarin Significant DDIs
complication in HIV-infected patients, which may be
between warfarin, protease inhibitors and NNRTIs may
due to a combination of increasing age, toxicity from
further increase the risk of significant hemorrhage.
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Antiretrovirals in the aging HIV population Nachega et al.
Clinically relevant DDIs between anticoagulants and
PI/r can significantly increase simvastatin
and lovastatin concentrations. Coadministration of these
exists as two isomers that differ in potency and route of
3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors
metabolism. S-warfarin is two to five times more potent
are not recommended due to the potential for rhabdo-
than R-warfarin. The more potent S-isomer is a CYP2C9
myolysis Moderate DDIs have been reported
substrate, whereas the R-isomer is metabolized via
with protease inhibitors and atorvastatin pravas-
CYP1A2 and CYP3A4 Induction properties of
NVP and lopinavir/RTV at steady state resulting in
monitoring and dose adjustment, these ‘statins’ can be
increased warfarin requirements have been reported .
safely coadministered with protease inhibitors.
RTV is a mixed CYP3A4 inhibitor and inducer and a mildCYP2C9 inhibitor. When RTV is added to a stable
The incidence of T2DM is increased in older HIV-
warfarin regimen, a supratherapeutic international nor-
infected individuals, which may be linked to long-term
malized ratio (INR) may result initially. However, at steady
use of ART Non-HIV infected elderly patients
state, subtherapeutic warfarin concentrations as a result of
65 years or older with diabetes were found to have a 36%
CYP3A4 induction may occur Although these
increased risk of developing hypoglycemia while receiv-
early reports used higher than currently recommended
ing sulfonylureas when compared with younger patients
doses of RTV, a 29% decrease in mean S-warfarin AUC was
This risk of hypoglycemia may be even higher in
also observed with darunavir/RTV (DRV/r; 600/100 mg
HIV-infected elderly patients due to the presence of DDI
twice daily) . In older patients, close INR monitoring
between oral hypoglycemics and antiretrovirals. There are
should be performed when boosted protease inhibitors or
limited DDI studies conducted with antiretroviral drugs
NNRTIs are added to a stable warfarin regimen.
and oral hypoglycemic medications; however, based onthe route of metabolism, there are some potentially
Dabigatran is a P-gp substrate, but not a substrate, inhibitor
significant DDIs PI/r may increase serum concen-
or inducer of CYP450 isoenzymes. Certain P-gp
inhibitors (e.g. ketoconazole, dronedarone) increase
dabigatran concentrations by approximately two-fold
contrary, EFV, ETR and NVP may decrease concen-
. PI/r may inhibit P-gp and may increase dabigatran
trations of these agents. Rosiglitazone can be considered
concentrations. Although clinical data are lacking, in
as an alternative agent with less potential for DDI with
patients with moderate renal impairment (creatinine
antiretrovirals Although DDI are unlikely to
clearance 15–30 ml/min), a lower dose of dabigatran
occur with metformin through CYP450 enzymes
should be considered in patients treated with boosted
declines in renal function due to increasing age,
antiretrovirals (e.g. tenofovir or HIV-associatednephropathy (HIVAN) can alter the serumconcentration of metformin, predisposing to serious sideeffects including lactic acidosis Interactions with a-glucosidase inhibitors (acarbose, miglitol) and antiretro-
Drug–drug interactions with medications
peptidase IV inhibitors, the saxagliptin dose should belimited to 2.5 mg once daily when coadministered with
Significant DDI between antiretrovirals and anti-
PI/r due to inhibition of CYP3A4-mediated metabolism
hyperlipidemic agents have been reported
of saxagliptin and linagliptin coadministration with
Table 1. Drug–drug interactions with antiplatelet and anticoagulant agents.
clopidogrel metabolite. Interaction unlikely
with: PI/r, NVP, EFV, RPV, RAL, MVC, NRTIs
PI/r may increase dabigatran concentrations in
patients with moderate to severe renal dysfunction;
dose reduction with CrCL 30–50 ml/min.
Interaction unlikely with: NNRTIs, RAL, MVC, NRTIs
DRV/r, LPV/r, NVP, EFV may decrease S-warfarin
ARV, antiretroviral; CrCL, creatinine clearance; DRV/r, darunavir/ritonavir; EFV, efavirenz; ETR, etravirine; INR, international normalized ratio;LPV/r, lopinavir/ritonavir; MVC, maraviroc; NRTI, Nucleoside Reverse Transcriptase Inhibitors; NNRTIs, Non-Nucleoside Reverse TranscriptaseInhibitors; NVP, nevirapine; PI/r, boosted PI; RAL, raltegravir; RPV, rilpivirine.
Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Table 2. Drug–drug interactions with antihyperlipidemic agents.
Atorvastatin AUC " 2.5, 5.8, and 9.4-fold
Avoid TPV/r with atorvastatin coadministration.
Other PI/r: start with atorvastatin 10 mg
once daily, and then titrate to effect. Do not
AUC # 43% with EFV co-administration.
exceed atorvastatin 20 mg with DRV/r, FPV/r,SQV/r. EFV, NVP, ETR: higher atorvastatindose may be needed.
Strong CYP3A4 inhibitor (e.g. itraconazole)
significantly increases lovastatinconcentrations 20-fold. PI/r mayalso significantly increase lovastatinconcentrations.
AUC 26 and 20%, respectively. ATV increases pitavastatin AUC 31%.
Higher pravastatin dose may be needed with
TPV/r, LPV/r, ATV/r increase rosuvastatin
PI/r: start with rosuvastatin 5 mg once daily,
AUC 37, 110, and 213%, respectively.
then titrate to effect. Maximumrecommended rosuvastatin dose 10 mg/daywith LPV/r and ATV/r co-administration.
SQV/r increases simvastatin AUC 31-fold.
higher simvastatin dose may be needed.
ATV, atazanavir; ATV/r, atazanavir/ritonavir; AUC, area under the plasma concentration time curve; DRV/r, darunavir/ ritonavir; EFV, efavirenz;ETR, etravirine; FPV/r, fosamprenavir/ritonavir; LPV/r, lopinavir/ritonavir; NVP, nevirapine; PI/r, protease inhibitor /ritonavir; TPV/r, tipranavir/ritonavir; SQV/r, saquinavir/ritonavir.
PI/r, EFV, ETR and NVP should be avoided
multifactorial and include low testosterone, older age,
Providers can consider using sitagliptin as an alternative
diabetes, neuropathy, drug use and depression
agent however, close monitoring of blood glucose
There are significant DDI between PI/r and drugs used
for erectile dysfunction Concentrations ofsildenafil tadalafil and vardenafil can allbe increased by 2.2–11-fold with PI/r. With PI/rcoadministration, dose adjustment of erectile dysfunctionagents is recommended to prevent unsafe drop in blood
Drug–drug interactions with medications
The prevalence of benign prostatic hyperplasia (BPH) ishigher in elderly patients. Biopsy confirmed BPH increasesfrom about 40 to 50% in men aged 51–60, to over 80% in
Drug–drug interactions with medications
men older than 80 years DDI with BPH medications
and antiretroviral drugs are shown in PI/r may significantly increase concentrations
Interactions with acid reducing agents and antiretroviral
of a-adrenergic antagonist such as alfuzosin and coadmi-
drugs are common in clinical practice. There have been
nistration is not recommended Tamsulosin is a
significant increases seen over time in the frequencies of
CYP3A4 and CYP2D6 substrate and its concentrations
reflux symptoms, gastroesophageal reflux disease and
were increased 2.8-fold when coadministered with a strong
Helicobacter pylori infections in HIV-infected individuals
CYP3A4 inhibitor (e.g ketoconazole) Similarly,
Additionally, HIV-infected individuals have been
other PI/r may increase tamsulosin concentration and
found to have elevated gastric pH values, which can lead
increase the risk of orthostatic hypotension (especially
to alteration in drug absorption Providers should
with the first dose). However, minimal interactions
be aware of clinically significant DDIs with acid-reducing
are expected between protease inhibitors and other a
antagonists (e.g. doxazosin, prazosin).
unboosted fosamprenavir nelfinavirtipranavir and rilpivirine These
Erectile dysfunction has been reported in up to 74%
antiretroviral drugs require an acidic environment for
of HIV-infected men The increased risks are
absorption; therefore, any acid suppressant therapy
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Antiretrovirals in the aging HIV population Nachega et al.
Table 3. Drug-drug interactions with genitourinary medications.
consider tamsulosin dosereduction with the first dose
AUC, area under the plasma concentration time curve; PI/r, protease inhibitor/ritonavir; RTV, ritonavir; IDV, indinavir.
(antacids, H2 receptor antagonists, proton pump inhibi-
The prevalence of HIV among psychiatric patients has
tors) has the potential to significantly reduce these
been reported to range from 8 to 19% and a
antiretroviral serum concentrations, which can poten-
significant proportion of patients with schizophrenia
tially lead to treatment failure of HIV. For example, the
engage in high-risk sexual behaviors that increase the risk
coadministration of ATV/RTV (ATV/r) with omepra-
of acquiring HIV Atypical antipsychotics are
zole resulted in a 76% decrease in ATV AUC
preferred over conventional (typical) antipsychotics in the
Although the manufacturer suggests that ATV/r can be
elderly population but studies specific to the HIV
safely coadministered with low-dose (20 mg) omeprazole,
population are lacking. The atypical antipsychotics are
most experts recommend switching to an alternative
associated with undesired metabolic effects (hyperglyce-
protease inhibitor such as DRV/r. Recommendations for
mia, hypercholesterolemia) and coadminsitration
the safe coadministration of these antiretroviral drugs with
with antiretroviral drugs that also increase risk of
metabolic effects (e.g. protease inhibitors and hyperlipi-
demia) can potentially increase the risk ofcardiovascular diseases in HIV-infected individuals. Several antipsychotics have significant DDI with anti-retrovirals and dosage reduction of the antipsychotic maybe required
Drug–drug interactions with medicationsused for central nervous system disorders
Depression and other psychiatric conditions are prevalentin
Drug–drug interactions with osteoporosis
infected elderly patients taking psychotropics, antidepress-
ants and benzodiazepines are at 78, 59 and 39% increasedrisk for fall, respectively However, treatment of
The prevalence of osteoporosis in HIV-infected individ-
depression is critical in the elderly HIV population because
uals has been found to be three-fold higher compared
untreated depression negatively impacts progression to
with HIV-negative individuals and the overall
AIDS and death in patients with HIV Selective
prevalence of patients with fracture was found to be
serotonin reuptake inhibitors (SSRIs) are commonly
2.87 vs. 1.77 per 100 persons in HIV-infected vs. HIV-
prescribed for depression in HIV-infected individuals
uninfected individuals (P < 0.0001) Tenofovir-
as they are better tolerated than tricyclic anti-
containing antiretroviral regimens have been associated
depressants (TCA). With protease inhibitor coadministra-
with larger decrease in spine and hip bone mineral density
tion, orthostatic hypotension and anticholinergic side
when compared with abacavir-containing regimens
effects from TCAs can result in severe morbidity .
There are also several clinically significant DDI with other
associated with a decrease in spine and hip bone mineral
antidepressants that warrant a dosage reduction of the
density First-line therapy for osteoporosis consists
of bisphosphonates, which have been demonstrated to be
efficacious in patients with HIV-associated osteoporosis
escitalopram and citalopram are preferred in HIV-infected
and there are no known DDI between bispho-
patients requiring antidepressant therapy due to less
sphonates and antiretrovirals. Calcium and vitamin D
supplementation is often recommended for bone health,
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Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Antiretrovirals in the aging HIV population Nachega et al.
Table 5. Drug–drug interactions with antidepressants / antipsychotics.
DRV/r decreased paroxetine AUC 39%, Titrate SSRI to effect. Escitalopram
and NVP can decrease fluoxetineconcentrations. EFV and DRV/rdecrease sertraline AUC by 39 and49%, respectively.
concentrations at steady state. Boosted PIs may increasevenlafaxine concentrations, whereasEFV, ETR, and NVP may decreasevenlafaxine concentrations. Ketoconazole (CYP3A4 inhibitor)increased desvenlafaxineAUC 43%. Boosted PIs mayincrease desvenlafaxineconcentrations.
increased appetite and weightgain which is beneficial inHIV-associated wastingsyndrome.
trazodone dose with slow titration). Monitor for nausea, dizziness,hypotension, and syncope. SQV/rcontraindicated with trazodone dueto risk of additive QT-prolongation. Consider alternative antidepressant(e.g. SSRIs)
dose. Consider alternativeantidepressant (e.g. SSRIs). Decrease maraviroc dose to150 mg b.i.d. with nefazodonecoadministration.
Tricyclic Antidepressant (TCA): Desipramine AUC increased 145%
closely for TCA toxicity. Avoid rilpivirinecoadministration with TCA due to riskof additive QT-prolongation.
Copyright Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
risperidone coadministration. RTVdecreased olanzapine AUC by 53%.
If coadministered with PIs, use with close
adverse drug reaction. Consider alternative
antipsychotic such as olanzapine. Pimozide
is contraindicated with PIs due to risk ofQT-prolongation. Avoid rilpivirinecoadministration with typical antipsychoticsdue to risk of additive QT-prolongation.
AUC, area under the plasma concentration time curve; PI, protease inhibitor; DRV/r, darunavir/ritonavir; FPV/r, fosamprenavir/ritonavir; LPV/r,lopinavir/ritonavir; TPV/r, tipranavir/ritonavir; SQV/r, saquinavir/ritonavir; RTV, ritonavir; NFV, nelfinavir; EFV, efavirenz; ETR, etravirine; NVP,nevirapine.
and significant DDI with calcium-containing products
population. Screening and management for other age-
and several antiretrovirals are outlined in
related comorbidities (e.g. diabetes, high blood pressure),depression, cognitive decline and substance abuse shouldbe a top priority. Several antiretroviral drugs exhibitinhibitory (protease inhibitors, DLV) and inducing (EFV,
ETR, NVP) effects on CYP450 isoenzymes, which areresponsible for the metabolism of many medications used
Management of ART in the aging HIV population is a
for the treatment of comorbidities in the aging HIV
therapeutic challenge from many different perspectives.
population. Awareness of common DDI among elderly
With increasing age, patterns of comorbidities are shifting
HIV-infected individuals are important to help prevent
to cardiovascular disorders, metabolic disorders, gastroin-
them and assure long-term success of ART. Healthcare
testinal/genitourinary disorders and psychiatric disorders.
providers should routinely screen patients’ medication lists
Treatment of these comorbidities introduces polyphar-
to look for significant DDIs and perform drug interaction
macy, increasing the risk of clinically significant DDIs,
checks using available online resources (e.g.
which can lead to adverse effects or treatment failure of
HIV. Although adherence tends to be higher in older
individuals compared to younger individuals, cognitive
the initiation of new medications in HIV-infected
impairment can impair adherence, leading to worse
individuals on ART. Although there are many drug
treatment outcomes. Also, polypharmacy can contribute
interaction studies documenting significant DDIs between
to medication fatigue. Healthcare providers caring for the
antiretroviral drugs and medications that are commonly
elderly HIV population should communicate to their
prescribed in the elderly population, the majority of these
patients the critical need for adherence to ART, its short-
pharmacokinetic studies were conducted in young,
term and long-term benefits and provide them with
healthy volunteers who are not HIV-infected. As a result,
practical monitoring tools to achieve high adherence levels
these studies may not be generalizable to elderly HIV-
for maximum viral suppression, halt of disease progression
infected patients. There is a need for investigations
and increase in quality of life. There is a need for targeted
specifically in HIV-infected individuals, including those
interventions to improve ARTadherence in the aging HIV
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Waikato Futures Symposium 15 July 2008 Further Reading New Zealand MAF (2008) Future Focus: Signposts to Success for New Zealand's Primary Industries , New Zealand Ministry of Agriculture and Forestry This project identified external drivers likely to impact on the agriculture, food and forestry sectors, and in the biosecurity setting, over the next two decades. The 6 key drivers of
STATISTICS IN MEDICINEStatist. Med. 2006; 25:127–141Published online 11 October 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/sim.2331Dichotomizing continuous predictors in multiple regression:Patrick Royston1; ∗ ; † , Douglas G. Altman2 and Willi Sauerbrei31MRC Clinical Trials Unit; 222 Euston Road; London NW1 2DA; U.K. 2Centre for Statistics in Medicine; Univers