Zidovudine and lamivudine reach higher concentrations in ventricular than in lumbar human cerebrospinal fluid.

OBJECTIVE: For the treatment of HIV-1-related brain disease and for the prevention of the brain becoming a viral reservoir, it is important that antiretroviral agents reach sufficient concentrations in the CNS. To date, human brain pharmacokinetic data are solely derived from lumbar cerebrospinal fluid (CSF) and mostly originate from single samples. DESIGN: We determined concentrations of antiretroviral drugs in serial samples of ventricular CSF and compared these to the concentrations in serum and lumbar CSF of these patients. METHODS: Two treatment-naïve HIV-1-infected patients received external ventricular drainage for obstructive hydrocephalus. Starting with a combination antiretroviral regimen (cART), ventricular CSF, and subsequently lumbar CSF, with parallel serum, was frequently collected. Drug concentrations were determined and CSF-to-serum ratios were calculated. RESULTS: High concentrations, resulting in high CSF-to-serum ratios, were found in the ventricular CSF of the three substances zidovudine, lamivudine and indinavir, whereas this was not observed for stavudine, ritonavir, saquinavir and efavirenz. Concentrations of zidovudine and lamivudine were up to four times greater in CSF from the ventricles than in lumbar CSF of the same patient. The zidovudine concentrations in the ventricular CSF exceeded serum concentrations by a factor of 1.4. CONCLUSION: Unexpectedly high concentrations of some antiretrovirals in the ventricular CSF, the site close to the brain parenchyma where HIV is located, should be considered when the cART regimen is aiming at CNS viral replication.

Stavudine entry into cerebrospinal fluid after single and multiple doses in patients infected with human immunodeficiency virus.

STUDY OBJECTIVE: To establish the pharmacokinetics of stavudine within the cerebrospinal fluid (CSF) of patients infected with human immunodeficiency virus (HIV). DESIGN: Pharmacokinetic study. SETTING: General clinical research center. PATIENTS: Thirty-six patients infected with HIV; 21 were receiving long-term stavudine therapy, 15 were not (single-dose treatment group). INTERVENTION: After an overnight fast, all patients received a single dose of stavudine 40 mg. Fifteen patients in the long-term treatment group and all 15 patients in the single-dose treatment group were randomized to undergo lumbar puncture 2, 4, or 6 hours after dosing (five patients for each time point from each group). The six other patients in the long-term treatment group underwent lumbar puncture 0 or 8 hours after dosing. MEASUREMENTS AND MAIN RESULTS: Serum stavudine concentrations were obtained just before dosing, 1 hour after dosing (approximate peak), and at the time of lumbar puncture. The CSF was also analyzed for cell counts, protein, and glucose levels. The mean peak serum stavudine concentration in the long-term treatment group was estimated to be 580.7 ng/ml (2.59 micromol/L), occurring approximately 1.3 hours after dosing. The CSF concentrations over 0-8 hours were 0.0-109.9 ng/ml (0.00-0.49 micromol/L) with an overall mean of 51.6 ng/ml (0.23 micromol/L). Mean peak CSF concentration was estimated to be 62.8 ng/ml (0.28 micromol/L), occurring 4.7 hours after dosing. For the 15 patients not taking stavudine, both the serum and the CSF estimated peaks were significantly lower than those of the long-term group: 475.3 ng/ml (2.12 micromol/L) and 40.4 ng/ml (0.18 micromol/L), respectively. However, time to peak was similar at 1.2 hours and 5.0 hours, respectively. In both groups, no correlation was found between CSF and baseline or peak serum stavudine concentrations, CSF white blood cell count, baseline CD4 + lymphocyte count, or plasma viral load. CONCLUSION: Mean CSF stavudine concentrations equaled or exceeded the mean concentration producing 50% of the maximal effect in vivo (EC 50 ) for HIV. The CSF concentrations were higher in the stavudine-experienced patients, indicating that concentrations rise with progressive doses until steady state is reached.

Liquid chromatographic-tandem mass spectrometric assay for the simultaneous determination of didanosine and stavudine in human plasma, bronchoalveolar lavage fluid, alveolar cells, peripheral blood mononuclear cells, seminal plasma, cerebrospinal fluid and tonsil tissue.

We have developed a sensitive, high-pressure liquid chromatographic-tandem mass spectrometric (LC/MS/MS) method for the simultaneous determination of didanosine (ddI) and stavudine (d4T) in human plasma, bronchoalveolar lavage fluid (BALF), alveolar cells (AC), peripheral blood mononuclear cells (PBMC), seminal plasma, cerebrospinal fluid (CSF), and tonsil tissue. Plasma, AC, PBMC and CSF were run with an isocratic HPLC method, while BALF supernatant, semen, and tonsil tissue utilized a gradient elution. Samples were prepared by solid phase extraction. Detection was by electrospray positive ionization with multiple reaction monitoring mode. The lower limits of quantitation for both ddI and d4T were 2.0 ng/ml in plasma; 0.5 ng/ml in CSF; 0.4 ng/ml in AC, PBMC, and BALF; 1.0 ng/ml in seminal plasma; and 0.01 ng/mg in tonsil tissue.

Making the most of sparse clinical data by using a predictive-model-based analysis, illustrated with a stavudine pharmacokinetic study.

A small-scale clinical investigation was done to quantify the penetration of stavudine (D4T) into cerebrospinal fluid (CSF). A model-based analysis estimates the steady-state ratio of AUCs of CSF and plasma concentrations (R(AUC)) to be 0.270, and the mean residence time of drug in the CSF to be 7.04 h. The analysis illustrates the advantages of a causal (scientific, predictive) model-based approach to analysis over a noncausal (empirical, descriptive) approach when the data, as here, demonstrate certain problematic features commonly encountered in clinical data, namely (i) few subjects, (ii) sparse sampling, (iii) repeated measures, (iv) imbalance, and (v) individual design variation. These features generally require special attention in data analysis. The causal-model-based analysis deals with features (i) and (ii), both of which reduce efficiency, by combining data from different studies and adding subject-matter prior information. It deals with features (iii)--(v), all of which prevent 'averaging' individual data points directly, first, by adjusting in the model for interindividual data differences due to design differences, secondly, by explicitly differentiating between interpatient, interoccasion, and measurement error variation, and lastly, by defining a scientifically meaningful estimand (R(AUC)) that is independent of design.

Evidence of a source of HIV type 1 within the central nervous system by ultraintensive sampling of cerebrospinal fluid and plasma.

Defining the source of HIV-1 RNA in cerebrospinal fluid (CSF) will facilitate studies of treatment efficacy in the brain. Four antiretroviral drug-naive adults underwent two 48-hr ultraintensive CSF sampling procedures, once at baseline and again beginning on day 4 after initiating three-drug therapy with stavudine, lamivudine, and nelfinavir. At baseline, constant CSF HIV-1 RNA concentrations were maintained by daily entry of at least 10(4) to 10(6) HIV-1 RNA copies into CSF. Change from baseline to day 5 ranged from -0.38 to -1.18 log(10) HIV-1 RNA copies/ml in CSF, and from -0.80 to -1.33 log(10) HIV-1 RNA copies/ml in plasma, with no correlation between CSF and plasma changes. There was no evidence of genotypic or phenotypic viral resistance in either CSF or plasma. With regard to pharmacokinetics, mean CSF-to-plasma area-under-the-curve (AUC) ratios were 38.9% for stavudine and 15.3% for lamivudine. Nelfinavir and its active M8 metabolite could not be accurately quantified in CSF, although plasma M8 peak level and AUC(0-8hr) correlated with CSF HIV-1 RNA decline. This study supports the utility of ultraintensive CSF sampling for studying HIV-1 pathogenesis and therapy in the CNS, and provides strong evidence that HIV-1 RNA in CSF arises, at least in part, from a source other than plasma.

Cerebrospinal fluid HIV-1 RNA during treatment with ritonavir/saquinavir or ritonavir/saquinavir/stavudine.

OBJECTIVE: To assess the HIV-1-RNA response and drug concentrations in cerebrospinal fluid (CSF) and serum during treatment with saquinavir (SQV)/ritonavir (RTV) or SQV/RTV plus stavudine (d4T) in HIV-1 -infected patients. DESIGN: A multicentre, open-label, randomized controlled trial. METHODS: A total of 208 protease inhibitor (PI) and d4T-naive, HIV-1-infected patients were treated with RTV 400 mg twice daily and SQV 400 mg twice daily with or without d4T 40 mg twice daily. Intensification with reverse transcriptase inhibitors was allowed if serum HIV RNA remained above 400 copies/ml after 12 weeks. In 27 volunteers, CSF and serum HIV RNA were measured at baseline, weeks 12 and 48, using the Roche Amplicor and the ultrasensitive assay. In 22 patients, serum and CSF drug concentrations were determined at week 12. RESULTS: The median baseline serum and CSF HIV-RNA concentrations were 4.81 and 3.21 log10 copies/ml, respectively. A difference in the proportion of patients with a CSF HIV-RNA level below the limit of quantification (< LLQ) after 12 weeks was found: four out of 14 (RTV/SQV) versus 12 out of 13 (RTV/SQV/d4T) (P = 0.001). The same results were found using the ultrasensitive assay. Patients with a baseline HIV-RNA level < LLQ in CSF remained < LLQ, regardless of the treatment regimen. Treatment with RTV/SQV alone was the only independent predictor of a CSF HIV-RNA level > LLQ at week 12 in logistic regression analysis (P = 0.005). CSF RTV and SQV concentrations were < LLQ in most patients. CONCLUSION: RTV/SQV alone cannot suppress detectable CSF HIV-1-RNA levels to < LLQ after 12 weeks of treatment in the majority of patients. CSF drug concentrations of RTV and SQV < LLQ may explain the suboptimal antiretroviral effect in the CSF.

The transport of the anti-HIV drug, 2',3'-didehydro-3'-deoxythymidine (D4T), across the blood-brain and blood-cerebrospinal fluid barriers.

1. The brain is a site of infection, viral replication and sanctuary for HIV-1. The treatment of HIV-1 infection therefore requires that an effective agent be delivered to the brain. 2',3'-Didehydro-3'-deoxythymidine (D4T) is a nucleoside analogue which has been shown to have beneficial clinical effects in the treatment of HIV infection. However, although D4T has been detected in human CSF, the ability of this drug to cross both the blood-brain and blood-cerebrospinal fluid (CSF) barriers and gain entrance into the brain tissue is not known. 2. This study examined the CNS entry of D4T by means of the bilateral vascular brain perfusion technique in the anaesthetized guinea-pig. 3. The results indicated that [3H]-D4T had a limited ability to cross the blood-brain barrier (BBB), which was not significantly greater than D-[14C]-mannitol (a slowly penetrating marker molecule). Although D4T was found to cross the blood-CSF barrier, the presence of D4T in the CSF did not reflect levels of the drug in the brain tissue. 4. These results can be related to the measured low lipophilicity of D4T, the higher paracellular permeability characteristics of the choroid plexus (blood-CSF barrier) compared to the BBB, and the sink action nature of the CSF to the brain tissue. 5. In conclusion, these animal studies suggest that D4T may only penetrate the brain tissue to a limited extent and consideration should be given to these findings in the clinical situation.

Direct transport of 2',3'-didehydro-3'-deoxythymidine (D4T) and its ester derivatives to the cerebrospinal fluid via the nasal mucous membrane in rats.

We investigated the absorption and transport of 2',3'-didehydro-3'-deoxythymidine (D4T) and its ester prodrugs from the nasal cavity in rats. The absorption of D4T and its acetate (C2-D4T) was rapid and almost complete, although the hemi-succinate (Suc-D4T) was absorbed rather slowly; the plasma concentrations of the prodrug, Suc-D4T, and regenerated D4T remained unchanged throughout the experimental period (180 min). Concentrations in the cerebrospinal fluid (CSF) following intravenous (i.v.) and intranasal (i.n.) administration were also measured. After i.n. administration, drug concentrations were higher in the fraction derived from the subarachnoid space located close to the nasal mucosa than those in the fractions located far from the nasal cavity. This difference was not found following the i.v. administration of the drugs. Following nasal administration, the intact Suc-D4T was found in the CSF at a concentration higher than that of D4T, although transport of the intact prodrug to the CSF was not observed following i.v. administration. These results suggest that direct transport of the drugs from the nasal cavity to the CSF significantly contributes to the higher concentrations in CSF of D4T and/or its ester prodrugs, and indicate the possible value of nasal administration for the treatment of patients with AIDS dementia.

A single-dose study to assess the penetration of stavudine into human cerebrospinal fluid in adults.

Penetration of stavudine into the cerebrospinal fluid (CSF) was studied in healthy humans. In this open, randomized study, a single oral dose of 40 mg of stavudine was given to 12 fasting volunteers > or = 18 years of age. Subjects were divided into three groups based on the time of CSF sampling (i.e., 0.75-1.25, 2-3, or 4-5 hours after dosing). Blood samples were collected over an 8-hour period after dosing and included a sample simultaneous with CSF collection to permit an estimate of CSF : plasma ratios. Stavudine concentrations in plasma and CSF were determined by a validated high-performance liquid chromatography method. Repeated measurements of vital signs, physical examination, and clinical laboratory tests indicated that the stavudine dose was well tolerated. CSF levels were not detected 0.75 to 1.25 hours after dosing. Thereafter, levels were detected in the CSF of five subjects; the mean concentration was 61 ng/ml. The mean CSF: plasma ratio increased with time, from 0.16 at 2 to 3 hours postdose in one subject to 0.40 at 4 to 5 hours postdose in four subjects. In conclusion, the mean stavudine concentration of 61 ng/ml achieved in the CSF of five subjects exceeds the ED50 of clinical isolates of HIV (230 nM, 52 ng/ml).

Cerebrospinal-fluid HIV-1 RNA and drug concentrations after treatment with lamivudine plus zidovudine or stavudine.

BACKGROUND: Treatment and prevention of HIV-1-related central-nervous-system disease may be dependent on penetration of antiretroviral drugs into the central nervous system. Few data are available about cerebrospinal-fluid penetration and concomitant changes of HIV-1-RNA concentrations during treatment with antiretroviral agents. We investigated these effects in HIV-1-infected people. METHODS: 28 antiretroviral-naive individuals with CD4 cell counts of 200/microL or more and plasma HIV-1-RNA concentrations of 10,000 or more copies/mL who were free of neurological symptoms were randomly assigned lamivudine plus either stavudine (n = 17) or zidovudine (n = 11). We did lumbar punctures on 28 individuals before and 22 individuals after 12 weeks of treatment to assess HIV-1-RNA and drug concentrations in cerebrospinal fluid. FINDINGS: All 28 individuals had detectable HIV-1-RNA concentrations in the cerebrospinal fluid (median 4.64 log10 copies/mL and 4.20 log10 copies/mL in the lamivudine plus zidovudine and lamivudine plus stavudine groups, respectively). There was no correlation between plasma and cerebrospinal-fluid HIV-1-RNA concentrations (r = 0.18, p = 0.35). After 12 weeks of treatment none of the individuals had detectable HIV-1-RNA concentrations in the cerebrospinal fluid. The highest drug concentration in the cerebrospinal fluid was for lamivudine followed by stavudine and zidovudine. Concentrations were consistent over time, unlike plasma concentrations. Therefore, we found time-dependent cerebrospinal-fluid to plasma drug-penetration ratios, which were highest for zidovudine followed by stavudine and lamivudine. INTERPRETATION: The two drug combinations were equally effective in the decrease of cerebrospinal fluid HIV-1-RNA concentrations. All drugs penetrated the cerebrospinal fluid. Antiretroviral drugs other than zidovudine might be useful in the prevention of AIDS dementia complex.

Microdialysis studies of the distribution of stavudine into the central nervous system in the freely-moving rat.

PURPOSE: To study the extent and time course of distribution of stavudine (d4T) into the central nervous system (CNS) and to investigate the transport mechanisms of antiviral nucleosides in the CNS. METHODS: Microdialysis with on-line HPLC analysis was used to measure drug concentrations in the brain extracellular fluid (ECF) and cerebrospinal fluid (CSF) in the freely-moving rat. The in vivo recovery of d4T and zidovudine (AZT) was estimated by retrodialysis, which was validated by the zero-net flux method. The CNS distribution of d4T was investigated during iv and intracerebroventricular (icv) infusion. In the subsequent studies, the effect of AZT on CNS distribution of d4T was examined. RESULTS: During iv infusion, d4T distributed rapidly into the CNS. Its brain ECF/plasma and CSF/plasma steady-state concentration ratios were 0.33 +/- 0.06 and 0.49 +/- 0.12, respectively (n = 15). During icv infusion, the steady-state d4T concentrations in the brain ECF were 23-fold higher than those during iv infusion, whereas its steady-state plasma levels were about the same for these two routes. Coadministration of AZT with d4T did not alter their respective brain distribution and systemic clearance at the concentrations examined. More importantly, the steady-state brain ECF/plasma and CSF/plasma concentration ratios of d4T were about 2-fold higher than those of AZT (0.15 +/- 0.04 and 0.25 +/- 0.08) determined in the same animals. CONCLUSIONS: d4T readily crosses the blood-brain barrier (BBB) and blood-CSF barrier. An active efflux transport system in the BBB and blood-CSF barrier may be involved in transporting d4T out of the CNS. Direct icv administration of d4T can be used to enhance its brain delivery. Moreover, d4T exhibits a more favorable penetration into the CNS than AZT and therefore may be useful in the treatment of AIDS dementia complex.