Medicine Chest: Combination Dosing Adjustments

by Glen Pietrandoni R.Ph.

The International AIDS Society-USA and the U.S. Department of Health and Human Services are continuously updating guidelines to help physicians and patients choose the best ways to use drugs in combinations for treating HIV/AIDS. You have probably seen the “one from column A and two from column B” charts that have been around for years. These tables have been a wonderful tool to determine treatment options for those newly diagnosed and treatment naïve. This is the basis of most treatment decisions for a patient’s first few drug regimens. How do physicians use the list of drugs to choose a drug regimen for patients with limited drug options? Sometimes drugs can be arranged together in ways to get more potent regimens, to cut down on pill count, or simply because there are no other choices at the time.

In the United States, it is the standard of care today to use phenotype and genotype testing to see which drugs are effective in halting viral replication in a particular patient. After a few drugs or drug classes are eliminated due to resistance (drug doesn’t work any longer), it may be more difficult to find a drug regimen that fits neatly on the DHHS guideline chart. Because HIV medicine is as much an “art” as it is a science, your provider may need to combine drugs together that normally would not be used in the same cocktail. When certain drugs are combined, adverse reactions can occur, but drug interactions are not always bad things. Again, sometimes agents can be combined to our benefit. The best example of this is when Norvir (ritonavir) is combined with other protease inhibitors. The drug level of these protease inhibitors are higher and last longer when taken with Norvir than using the drug without Norvir. The benefits often include better viral control and lower pill burden. The downside of throwing all these drugs together can mean an increase in side effects if the blood levels go too high. Always communicate with your health care team to let them know what’s going on. Remember, while most side effects can be managed and are temporary, more serious complications may require a change in therapy. There still needs to be that target of 95% adherence to achieve maximal viral suppression and get those T-cells up!

The combination drug chart shows some optional ways to combine drugs with each other. Some combinations have more data to support their use, while other combinations are only now being studied for the first time. Some of these regimens are not yet FDA approved, but many physicians treating HIV/AIDS have experience in using regimens “off label” with some success. As always, learn about your treatment options and discuss the benefits and disadvantages of a new regimen before you start taking the medication.

Glen Pietrandoni is director of Clinical Pharmacy Services for the Walgreens Specialty Pharmacy, focusing on HIV, located in the Howard Brown Health Center of Chicago. Contact: Glen.Pietrandoni@walgreens.com.

KEY

RTV =

Norvir (ritonavir)

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