New Drugs Coming Down the Pike

by Glen Pietrandoni, R.Ph.

“Once” upon a time…the alarm clock had to be set every few hours, 24/7, as a reminder to take a dose of AZT. You got through it. Then came combination therapies, 12 pills at a time, three times a day, with food, plus a few others on an empty stomach a couple of hours later. You got through it. Then came along Crixivan every 8 hours or chewable Videx twice a day. Once again you got through it. Norvir liquid, enough said. At last, there is some good news. Once daily dosing is here for some drug products and just around the corner are quite a few more drugs.

Ideally, drugs that can be dosed once a day must be very potent, have minimal side effects, and should be “forgiving” for late or missed doses. In order to allow prescription drugs to be brought to market quicker, pharmaceutical companies file for Food and Drug Administra-tion (FDA) approval before dosing studies are finished. Once the drugs are on the market, they are still being studied in order to get approval for easier dosing. In some situations, clinicians can use pharmacokinetic (PK) data to make educated adjustments in dose and will prescribe drugs with “off label” directions. Basically, PK data tells us how much drug is in the blood and for how long. Blood levels need to be above a minimum level to be effective, but not too high as to cause toxic effects.

For example, because blood levels remain high for Viracept, it is now approved for twice daily dosing (5 tablets twice daily, instead of 3 tablets three times daily). Other times, the FDA rejects changes to originally approved dosing regimens, as in the case of Crixivan. Twice daily dosing of Crixivan did not show high enough levels of drug and the virus became resistant to the drug. Unless used in combination with other protease inhibitors, Crixivan is only approved for dosing every 8 hours, and never twice daily.

Before you get too excited about the possibility of leaving all your medicine at home and feeling free of the ball and chain, there are a few things you must know. If daily dosing were available, then each daily dose of the drug would become even more important. With adherence needing to be above the 95% level, even two missed doses per month could put you at risk for viral resistance and drug failure. It may also be important to be consistent with the time of the dose from day to day. The window for taking medication may not be much more flexible than 24 hours so drugs must be taken at the same time every day. The studies being conducted on once-a-day dosing regimens will address these issues, so don’t try this at home. Only your doctor can change the way to take your prescription drugs.

As mentioned, there is a large effort by the pharmaceutical companies to make taking the drug cocktails easier for people to handle. It has been shown that a simple regimen is easier to take and is effective for a longer period of time than more complex drug therapies. (Duh). But until once a day dosing is available, you’ll get through it.

Glen Pietrandoni is director of Clinical Pharmacy Services for the HIV-specialty Walgreens pharmacy located in the Howard Brown Health Center of Chicago.

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