Fact Sheet 409

Combination Medications

WHAT ARE COMBINATION MEDICATIONS?
PK BOOSTERS
1. COMBINATIONS OF REVERSE TRANSCRIPTASE INHIBITORS ("NUKES")
2. COMBINATIONS OF A NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR AND REVERSE TRANSCRIPTASE INHIBITORS
3. COMBINATIONS OF PROTEASE INHIBITORS
4. OTHER COMBINATIONS IN DEVELOPMENT

WHAT ARE COMBINATION MEDICATIONS?

Combination medications are pills or tablets that contain more than one medication to fight HIV. They are listed in the tables below. Pharmaceutical companies have been working hard to make their medications easier to take. Part of this effort has been to combine more than one medication in a single pill. These combinations are referred to as fixed-dose combinations, or FDCs.

The first FDC to treat HIV was Combivir by ViiV Healthcare*. Combivir contains two nucleoside analog reverse transcriptase inhibitors. This was followed by Trizivir, also by ViiV Healthcare, which includes 3 nukes.  Some antiviral products are only available outside the US through the US President's Emergency Plan for AIDS Relief (PEPFAR.) For more information, see fact sheet 475 or http://www.pepfar.gov.

Be sure that you do not take a combination medication along with any of its components! For example, do not take Truvada with tenofovir (Viread) or emtricitabine (Emtriva); do not take Combivir along with zidovudine (Retrovir) or lamivudine (Epivir.)

WHAT ARE PK BOOSTERS?

When some medications are taken by mouth, their levels in the blood are very low. For them to fight HIV, they have to be taken at high doses. Another possibility is to "boost" their blood levels. This is done by slowing down the processing (metabolism) of these drugs. A drug that slows down the metabolism is called a "PK booster." PK stands for pharmacokinetic. This refers to the way that medications are processed by the body.

The first PK booster used in HIV was ritonavir by Abbott. Ritonavir slows down the metabolism of many drugs by the liver. This increases the blood levels of some anti-HIV medications so that a lower dose can be taken. However, it can also increase blood levels of many other drugs. In some cases, this can cause a harmful overdose.

A second PK booster is being developed by Gilead Sciences, called GS-9350, is in Phase II trials. Other PK boosters in Phase I trials include PF-03716539 by ViiV Healthcare, SPI-452 by Sequoia, and TMC558445 by Tibotec Pharmaceuticals.

1. COMBINATIONS OF REVERSE TRANSCRIPTASE INHIBITORS ("NUKES")

2. COMBINATIONS OF A NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR AND REVERSE TRANSCRIPTASE INHIBITORS

3. COMBINATIONS OF PROTEASE INHIBITORS (NOTE: a small dose of ritonavir is used to boost blood levels of other protease inhibitors. The amount of ritonavir is not high enough to fight HIV.)

4. OTHER COMBINATIONS IN DEVELOPMENT

*Year of approval of the first version of the combination. More information on medications approved as part of the US President's Emergency Plan for AIDS Relief is available at http://www.fda.gov/oia/pepfar.htm 

*ViiV Healthcare is a new HIV company. It is a joint venture of Pfizer and GlaxoSmithKline.