Dose-finding study of once-daily indinavir/ritonavir plus zidovudine and lamivudine in HIV-infected patients.
BACKGROUND
Strategies for treatment of HIV need to be considered in terms of combining potency, safety, and convenience of dosage. However, regimens including once-daily protease inhibitors are not yet available. We have performed a pilot study to determine an indinavir/ritonavir (IND/RTV) regimen for once-daily dosing, by monitoring plasma levels.


METHODS
Antiretroviral-naive HIV-infected adults were eligible. Therapy was zidovudine/lamivudine 1 pill twice daily plus IND/RIT (liquid formulation) 800/100 mg twice daily with food. At 4-week intervals, plasma levels were measured and dosage of IND/RIT switched to 1000/100 mg daily and then 800/200 mg daily. If 12-hour minimum concentrations (Cmin12h) of IND were too low (<0.1 microg/ml) with IND/RIT 1000/100 mg once daily in the first half of the patients, it was planned to switch directly to 800/200 mg once daily in the other half.


RESULTS
In all, 27 patients were recruited. Mean baseline CD4+ lymphocyte count was 107 x 106/L (range, 4-623 x 106/L). Eleven patients (40%) discontinued the study medication within the first 4 weeks due to clinical progression (n = 3) or grade 1-2 RTV related side effects (n = 8). Nine patients (group A) switched from 800/100 mg twice daily to 1000/100 mg once daily and then to 800/200 mg once daily. Seven patients (group B) switched directly to 800/200 mg once daily. At week 32, viral load was <5 copies/ml in 15 of 16 patients (94%). RTV levels were always <2.1 microg/ml. The mean and 95% confidence interval for IND Cmin and Cmax in microg/ml was: using IND/RTV 800/100 mg twice daily (n = 16) 1.4 (0.5-2.3) and 6.7 (4.4-9.1), respectively; using IND/RTV 1000/100 mg once daily (n = 9) 0.18 (0-0.41) and 8.6 (3.3-14), respectively; and using 800/200 mg once daily (n = 16) 0.38 (0-0.9), and 7.5 (0.8-14.8). For all 16 patients who received IND/RTV 800/100 mg twice daily, the Cmin value for IND was >/=0.1 microg/ml. Conversely, IND Cmin was <0.1 microg/ml in 4 of 9 receiving 1000/100 mg once daily but in only 1 of 16 receiving 800/200 mg once daily.


CONCLUSIONS
Once-daily regimen of IND/RIT is feasible and deserves further evaluation in larger randomized trials. Liquid formulation of RIT was not well tolerated by our antiretroviral-naive patients despite lower than suggested doses.
Mallolas
J
J
Infectious Diseases, Clinical Pharmacology, Pharmacy, and Microbiology Services, Institut D'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Fundació Clínic, Barcelona, Spain. jmallolas@medicina.ub.es
Blanco
J L
JL
Sarasa
M
M
Giner
V
V
Martínez
E
E
García-Viejo
M A
MA
Arnaiz
J A
JA
Cruceta
A
A
Soy
D
D
Tuset
M
M
Soriano
A
A
Codina
C
C
Pumarola
T
T
Carné
X
X
Gatell
J M
JM
D000328:Adult; D018791:CD4 Lymphocyte Count; D004359:Drug Therapy, Combination; D015658:HIV Infections / Q000188:drug therapy*; D017320:HIV Protease Inhibitors / Q000008:administration & dosage; D006801:Humans; D019469:Indinavir / Q000008:administration & dosage*; D019259:Lamivudine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage; D019438:Ritonavir / Q000008:administration & dosage* / Q000009:adverse effects; D019562:Viral Load; D015215:Zidovudine / Q000008:administration & dosage*
D017320:HIV Protease Inhibitors; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D015215:Zidovudine; D019469:Indinavir; D019438:Ritonavir