Coadministration of etravirine and raltegravir (400 mg twice daily) decreased raltegravir AUC, C12 and Cmax by 10%, 34% and 11% respectively. Etravirine AUC, C12 and Cmax increased by 10%, 17% and 4%, respectively These findings can be extended to raltegravir 1,200 mg once daily. No dosage adjustment is required raltegravir (400 mg twice daily and 1,200 mg once daily) or etravirine.
Isentress 600 mg Summary of Product Characteristics, Merck Sharp & Dohme Ltd, September 2021.

Etravirine did not have a clinically meaningful effect on the pharmacokinetics of 400 mg twice daily raltegravir. Coadministration of etravirine (200 mg twice daily) and raltegravir (400 mg twice daily) decreased raltegravir Cmax, AUC and Cmin by 11%, 10% and 34% (n=19). In drug interaction studies performed using raltegravir film-coated tablets 400 mg twice daily dose, raltegravir did not have a clinically meaningful effect on the pharmacokinetics of etravirine (Cmax, AUC and Cmin increased by 4%, 10% and 17%; n=19). No dose adjustment is required when raltegravir 400 mg twice daily is coadministered. Coadministration with once daily raltegravir is not recommended.
Isentress Prescribing Information, Merck & Co Inc, August 2021.

Etravirine and raltegravir can be used without dose adjustments. Coadministration with raltegravir (400 mg twice daily) decreased raltegravir AUC (10%), Cmax (11%) and Cmin (34%). Etravirine AUC, Cmax and Cmin increased by 10%, 4% and 17%, respectively.
Intelence Summary of Product Characteristics, Janssen-Cilag Ltd, March 2019.

The interaction between etravirine and raltegravir was evaluated in clinical studies and no dose adjustment is needed for either drug. Coadministration of raltegravir (400 mg twice daily) and etravirine was studied in 19 subjects. Etravirine Cmax, AUC and Cmin increased by 4%, 10% and 17% respectively; raltegravir Cmax, AUC and Cmin decreased by 11%, 10% and 34%, respectively.
Intelence US Prescribing Information, Janssen Therapeutics, July 2019.

Four cases in HIV+ subjects have been reported recently where lower than anticipated raltegravir concentrations were observed when given with etravirine. The first case had raltegravir trough concentrations of 189 and 313 ng/ml on two occasions whilst on darunavir/ritonavir, enfuvirtide and raltegravir. After switching enfuvirtide for etravirine, raltegravir trough concentrations decreased to 10 ng/ml and then to 5 ng/ml one month later. The second case started a combination of tenofovir/emtricitabine, etravirine and raltegravir. Tenofovir trough concentrations were in the expected range, but raltegravir trough concentrations were considered low (30 ng/ml). Increasing raltegravir from 800 mg/day to 1200 mg/day resulted in an increase in trough concentration (67 ng/ml). The third case had low raltegravir trough concentrations on two occasions (12 and 9 ng/ml) whilst receiving darunavir/ritonavir, etravirine and raltegravir. The final case switched to tenofovir, etravirine and raltegravir. Etravirine trough concentrations were within the normal range, but raltegravir trough concentrations were low (29 ng/ml). In all these cases, raltegravir concentrations were below the mean trough concentration previously observed in initial clinical trials (63 ng/ml, range 29-118 ng/ml; Markovitz et al, JAIDS, 2006, 43: 509-515). In two of the cases, concentrations were below the in vitro IC95 for raltegravir of 14.6 ng/ml.
Etravirine-raltegravir, a marked interaction in HIV-1 infected patients: about four cases. Menard A, Solas C, Mokthari S, et al. AIDS, 2009, 23(7): 869-871.

As raltegravir is primarily glucuronidated and TMC125 induces glucuronidation, an interaction study was performed in HIV- subjects (n=19) with raltegravir (400 mg twice daily) and TMC125 (200 mg twice daily). Raltegravir had no significant effect on TMC125 pharmacokinetics (increases in AUC by 10%, Cmax by 4%, Cmin by 17%). Raltegravir exposure was decreased by 10% (AUC), 11% (Cmax) and 34% (Cmin), possibly via induction of glucuronidation. Coadministration was generally safe and well tolerated and no dose adjustment is necessary in HIV+ subjects.
Pharmacokinetic evaluation of non-nucleoside reverse transcriptase inhibitor TMC125 and integrase inhibitor raltegravir in healthy subjects. Anderson MS, Kakuda TN, Miller JL, et al. 4th IAS Conference on HIV Pathogenesis, Treatment & Prevention, Sydney, July 2007, abstract TUPDB02.