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Pharmacokinetics of Oral Contraceptive Unaffected by Coadministration of Raltegravir: Presented at ICAAC

By Ed Susman

CHCIAGO, IL -- September 21, 2007 -- Coadministration of the investigative integrase inhibitor raltegravir and oral contraceptives does not appear to create any clinically significant impact on the pharmacokinetics of the drugs.

Researchers for Merck & Co., the developers of raltegravir, enrolled 20 healthy women in a randomized, placebo-controlled, two-period, crossover study to study the impact of combining the anti-HIV drug raltegravir with a contraceptive during three menstrual cycles.

"We actually did a survey to make sure we selected one of the major birth control pills for this study," said Marian Iwamoto, MD, PhD, Director of Clinical Pharmacology, Merck & Co., Inc., Whitehouse Station, New Jersey, speaking here at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

In the study, the women were first randomized to raltegravir 400 mg twice daily on days 1 through 21 of each treatment period or a placebo and were also given Ortho Tri-Cyclen (ethinyl estradiol/ norgestimate) on days 1 to 28 (21 days of active contraception followed by 7 days of placebo) during each treatment period.

Plasma concentrations were evaluated over 24 hours postdose on day 21 of each treatment period. Blood levels of the two drugs were calculated along with possible interactions between the drugs. Nineteen women completed the trial.

"We did notice that when the two drugs were administered together, the maximum level of raltegravir in the blood appeared to be elevated," Dr. Iwamoto said at her poster presentation on September 19th. "However, we do not think that this increase is clinically meaningful."

Based on assessment of clinical and laboratory adverse experiences, multiple oral doses of 400-mg raltegravir given in combination with a triphasic oral contraceptive containing ethinyl estradiol and norgestimate were generally well tolerated, Dr. Iwamoto said. No serious clinical or laboratory adverse events were reported.

"The results of this study indicate that Tri-Cyclen can be safely and effectively coadministered with raltegravir," she concluded.

Raltegravir is now under review by the US Food and Drug Administration.


[Presentation title: Effect of Raltegravir (RAL) on the Pharmacokinetics (PK) of Oral Contraceptives. A-1425]

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