Comorbidities, Drug Interactions, and other considerations

Comorbidity and Co-medication Interactions

  • DISCLAIMER: HIV-ASSIST Inc. is not a comprehensive drug-interaction guide and does not independently assess each drug interaction.  The site does not assess multi-way interactions.
  • HIV-ASSIST seeks to facilitate access to information from clinical practice guidelines and other resources regarding drug interactions. Information contained on HIVASSIST is often taken directly from other sources, and sometimes summarized or annotated. HIVASSIST makes no claims about the accuracy of this process and relies on a volunteer team, including pharmacists.  
  • Interaction information draws on information presented in any or all of the following: US DHHS guidelines , FDA package insert labeling, US National HIV curriculum, as well as the University of Liverpool HIV Drug interaction guide.
  • The HIV-ASSIST team and Scientific Advisory Panel volunteer pharmacy working group assesses HIVA-ASSIST Utility Weights for each drug interaction.  In general, minor drug interactions requiring no dose adjustments are graded with a utility penalty of 0-0.5.  Minor interactions requiring dose adjustment are generally graded a utility penalty of 0.5-1.0.  Moderate or severe interactions which could compromise effectiveness of an ART or comedication, with or without drug interaction, OR those situations for which there is more limited data are generally graded between 1.0-2.0.  Interactions considered 'contraindicated' by most guidelines or other sources are excluded from consideration.  
  • In several instances (e.g., rifamycins), clinical practice guidelines have heterogeneity and may disagree. In these instances, the HIV-ASSIST team urges clinical consultation with an expert. Utility weights represent an attempt to reconcile available information, informed by the Scientific Advisory Panel.
  • Comorbidities information is drawn largely from US DHHS guidelines , FDA package insert labeling, and US National HIV curriculum.
  • Each comorbidity is considered for its impact on clinical decision making related to specific ART selection and is assigned an HIVASSIST utility weight

ART Interactions

We additionally assign penalties to the base score of regimens that have undesired interactions between various drugs within the regimen. These penalties are drawn from DHHS guidelines and also range from 0 to less than 2. Regimens that contain ART interactions with 2 or above are excluded.

Pill Burden Penalty

We incorporate a penalty based on total pill count and maximum dosing frequency to prioritize regimens with the lowest pill burden, as shown in the equation below. For example, a single pill combination regimen (e.g., Genvoya; TAF/FTC/EVG/c) would not have an added penalty, whereas a regimen with 3 pills with maximum bid dosing would have an added penalty of 1 to the base score.

Pill Burden Equation


Regimens with ABC are excluded if the HLA-B5701 status is either positive or unknown.


We only display MVC-containing regimens if the patient has a R5 virus strain.

Less Preferred ARVs

We assign penalties to less preferred ARVs as shown below.

Score Modification Rule (Click to expand)
We gave preference to DTG and BIC over EVG, DRV over ATV, RPV over ETR (and other 2nd generation NNRTIs), and TAF over TDF
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We gave preference to TAF/TDF over ABC when ABC was not paired with DTG
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We gave preference to DTG and BIC over RAL, DRV among PI’s over LPV, and gave preference to EFV over other 1st generation NNRTI’s
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We gave preference to DRV among PI’s over older PI’s, such as IDV, NFV, SQV, FPV, or TPV
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Given toxicities, we heavily penalized older NRTIs such as AZT, D4T, and DDI
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Other Considerations

For regimens with two NRTIs, we only display regimens with combinations of TAF/FTC (or TDF/FTC) or ABC/3TC due to the availability of combination pills.

For XTC-containing regimens with only 1 NRTI, we only display the 3TC-containing regimen if both XTC-containing regimens have equal weighted scores.

For regimens that only differ in the inclusion of DTG or RAL, we only display the DTG-containing regimen if the RAL- and DTG-containing regimen have equal weighted scores.