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PubMed1998

Identification of drug metabolites in biological matrices by intelligent automated liquid chromatography/tandem mass spectrometry.

A rapid and systematic strategy for the identification of drug metabolites in biological matrices based on liquid chromatography-tandem mass spectrometry (LC/MS/MS) techniques was utilized for the identification of drug metabolites of the HIV protease inhibitor Indinavir. This strategy integrates intelligent realtime mass spectrometry with HPLC detection and a predictive strategy for detecting metabolites arising from common biotransformations, to rapidly elucidate structures of drug metabolites. Structures of metabolites generated from in vitro incubation mixtures of Indinavir were characterized from a single chromatographic analysis using the automated LC/MS/MS methodology, thus reducing data acquisition time and improving efficiency.

Animals↗
PubMed2003

Anti-retroviral protease inhibitors--'a two edged sword?'.

The use of anti-retroviral protease inhibitors in combination with nucleoside analog or non nucleoside reverse transcriptase inhibitors (HAART) has led to dramatic decreases in the mortality seen with HIV infected patients. In concert with these treatment regimens, especially with the inclusion of the anti-retroviral protease inhibitors (PI), a complex series of metabolic complications occurred. These included alterations of fat and carbohydrate metabolism. In some patients, one could observe either lipoatrophy (fat wasting) as well as lipohypertrophy (fat deposition) or both. The problem is that the lack of a case definition of the altered fat metabolism confuses diagnoses. In vitro, interference with fat cell differentiation has been demonstrated by PI. Further, in vitro studies demonstrate that indinavir, a PI currently used in HIV treatment, can interact with the insulin responsive glucose transporter (GLUT4). The activity of the GLUT4 is inhibited by indinavir and eventual insulin resistance has been shown (i.e. in vivo and in vitro). Also, controversy exists regarding insulin signaling in fat cells. Finally, the relationships between hyperlipidemia and/or lipolysis and altered carbohydrate metabolism (i.e. mild glucose intolerance, insulin resistance) suggest an association with cardiovascular risk in protease treated patients (Metabolic Syndrome X). In short, while multiple problems exist, no one mechanism can account for the changes observed.

Adipose Tissue↗
PubMed2000

Kinetic analysis of the interaction between HIV-1 protease and inhibitors using optical biosensor technology.

The interaction between HIV-1 protease and reversible inhibitors was studied by surface plasmon resonance biosensor technology. The steady-state binding level and the time course of association and dissociation could be observed by measuring the binding of inhibitors injected in a continuous flow of buffer to the immobilized enzyme. Fourteen low molecular weight inhibitors (500-700 Da), including the four clinically used HIV-1 protease inhibitors (indinavir, nelfinavir, ritonavir, and saquinavir), were analyzed. Affinities were estimated as B(50) values from a series of sensorgrams at different concentrations of inhibitors. These values were found to be correlated with inhibition constants (K(i)) determined by an enzyme inhibition assay (r(2) = 0.84, logarithmic values). Dissociation rates were estimated at a single saturating concentration of the inhibitors as t(1/2,obs), but these values did not correlate with K(i) (r(2) = 0.26, logarithmic values). Indinavir had the highest affinity (B(50) = 11 nM) and the fastest dissociation (t(1/2,obs) = 500 s) among the clinically used inhibitors while saquinavir had a lower affinity (B(50) = 25 nM) and the slowest dissociation rate (t(1/2,obs) = 6500 s). Since these two inhibitors have similar K(i) values, the differences in dissociation rates reveal important characteristics in the interaction that cannot be obtained by the inhibition studies. The biosensor data are expected to be of greater in vivo relevance since the experiments were performed in a buffer more similar to physiological conditions.

Drug Design↗
PubMed2001

Determination of interaction kinetic constants for HIV-1 protease inhibitors using optical biosensor technology.

The interaction between HIV-1 protease and inhibitors has been studied with optical biosensor technology. Optimized experimental procedures and mathematical analysis permitted determination of association and dissociation rate constants. A sensor surface with native enzyme was unstable and exhibited a drift that was influenced by the binding of inhibitor. This was hypothesized to be due to a specific mechanism involving autoproteolysis and/or dimer dissociation. The use of a mutant predicted to be less susceptible to autoproteolysis (Q7K) than wild-type enzyme resulted in a minor effect on surface stability, while a completely stable surface was obtained by treatment of the immobilized enzyme with N-ethyl-N'-(dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide; the most stable surface was achieved by chemically modifying the Q7K enzyme. The stabilized surface was enzymatically active and the interaction with inhibitors was similar to that for native enzyme. Several of the inhibitors had very high association rates, and estimation of kinetic constants was therefore performed with a binding equation accounting for limited mass transport. Of the clinical inhibitors studied, saquinavir had the highest affinity for the enzyme, a result of the lowest dissociation rate. Although the dissociation rate for ritonavir was sixfold faster, the affinity was only twofold lower than that for saquinavir since the association rate was threefold faster. Nelfinavir and indinavir exhibited lower affinities relative to the other inhibitors, a consequence of a slower association for nelfinavir and a relatively fast dissociation for indinavir. These results show that biosensor-based interaction studies can resolve affinity into association and dissociation rates, and that these are characteristic parameters for the interaction between enzymes and inhibitors.

Amino Acid Substitution↗
PubMed1999

Microbial conversion of indene to indandiol: a key intermediate in the synthesis of CRIXIVAN.

Indene is oxidized to mixtures of cis- and trans-indandiols and related metabolites by Pseudomonas putida and Rhodococcus sp. isolates. Indene metabolism is consistent with monooxygenase and dioxygenase activity. P. putida resolves enantiomeric mixtures of cis-1,2-indandiol by further selective oxidation of the 1R, 2S-enantiomer yielding high enantiomeric purity of cis-(1S, 2R)-indandiol, a potential intermediate in the synthesis of indinavir sulfate (CRIXIVAN), a protease inhibitor used in the treatment of AIDS. Molecular cloning of P. putida toluene dioxygenase in Escherichia coli confirmed the requirement for the dihydrodiol dehydrogenase in resolving racemic mixtures of cis-indandiol. Rhodococcus sp. isolates convert indene to cis-(1S, 2R)-indandiol at high initial enantiomeric excess and one isolate also produces trans-(1R, 2R)-indandiol, suggesting the presence of monooxygenase activity. Scale up and optimization of the bioconversions to these key synthons for chiral synthesis of potential intermediates for commercial manufacture of indinavir sulfate are described.

Drug Design↗
PubMed2000

Fitness of human immunodeficiency virus type 1 protease inhibitor-selected single mutants.

Human immunodeficiency virus type 1 (HIV-1) evolution under chemotherapeutic selection pressure in vivo involves a complex interplay between an increasing magnitude of drug resistance and changes in viral replicative capacity. To examine the replicative fitness of HIV-1 mutants with single, drug-selected substitutions in protease (PR), we constructed virus that contained the most common mutations in indinavir-selected clinical isolates, PR M46I and V82T, and the most common polymorphic change in drug-naïve patients, PR L63P. These mutants were competed in vitro in the absence of drug against the otherwise isogenic WT virus (NL4-3). Phenotypic drug susceptibility was determined with a recombinant virus assay using a single cycle of virus growth. PR M46I and L63P were as fit as WT. However, PR V82T was out-competed by WT. None of these mutants had appreciable phenotypic resistance to any of the protease inhibitors, including indinavir. The PRV82T mutant was hypersusceptible to saquinavir. Thus, the impaired fitness of the V82T single mutant is consistent with its low frequency in protease inhibitor-naïve patients. The similar fitness of WT (NL4-3), L63P, and M46I is consistent with the common occurrence of L63P in the absence of protease inhibitor-selection pressure, but not with the rare detection of M46I in drug-naïve patients.

Drug Resistance, Microbial↗
PubMed2004

Direct interference of HIV protease inhibitors with pancreatic beta-cell function.

The aim of the present study was to evaluate whether HIV protease inhibitors directly interfere with stimulus-secretion coupling in pancreatic beta-cells. Insulin secretion was determined by a radioimmunoassay (RIA), cytosolic free Ca2+ concentration ([Ca2+]c) with the fluorescence dye fura-2 and whole-cell membrane currents with the patch-clamp technique. Glucose-induced insulin secretion was inhibited in a concentration-dependent manner by ritonavir and nelfinavir but not by indinavir. Ritonavir and nelfinavir lowered [Ca2+]c in the presence of a stimulatory glucose concentration whereas indinavir again had no effect. Ritonavir and nelfinavir completely inhibited the effect of tolbutamide, which normally increases [Ca2+]c by blocking KATP channels. This observation points to an action of both drugs on KATP channels or a step distal to these channels in stimulus-secretion coupling. Ritonavir was used to further evaluate the direct effects of HIV protease inhibitors on beta-cell ion channel currents. Unexpectedly, ritonavir inhibited neither the whole-cell KATP current nor the whole-cell L-type Ca2+ current. Tolbutamide almost completely suppressed the KATP current in the presence of ritonavir excluding that ritonavir alters the tolbutamide sensitivity of the KATP channel. Ritonavir increased the length and decreased the frequency of glucose-induced action potentials. This effect can be attributed to inhibition of voltage-dependent K+ currents. Intracellular stores seem not to be involved in the ritonavir-induced lowering of [Ca2+]c. In conclusion, different HIV protease inhibitors surprisingly reveal distinct effects on insulin secretion. Ritonavir inhibits insulin secretion by lowering [Ca2+]c but this effect is evidently independent of the opening of KATP channels or the closure of voltage-dependent Ca2+ channels, which are commonly considered to play a key role in stimulus-secretion coupling.

Animals↗
PubMed2004

Maternal-fetal transfer and amniotic fluid accumulation of protease inhibitors in pregnant women who are infected with human immunodeficiency virus.

OBJECTIVE: The purpose of this study was to investigate placental transfer and amniotic fluid concentrations of protease inhibitors when they are given to pregnant women who are infected with human immunodeficiency virus. STUDY DESIGN: Fifty-eight mothers who received antiretroviral therapy that included > or =1 protease inhibitors for clinical indications at the time of delivery were enrolled in the study. Maternal blood samples and amniotic fluid were obtained during delivery or cesarean delivery, and paired cord blood samples were obtained by venipuncture immediately after the delivery. Drug concentrations were measured with high performance liquid chromatography. RESULTS: Most maternal protease inhibitor plasma concentrations (38/66 concentrations) were below the trough concentrations that are recommended for therapeutic drug monitoring. Cord blood concentrations were below the assay limit of detection in 10 of 40 samples for nelfinavir and 25 of 40 samples for its metabolite M8, 9 of 11 samples for ritonavir, 4 of 6 samples for indinavir, 5 of 6 samples for saquinavir but were detectable in 3 of 3 samples for amprenavir. Among the 24 amniotic fluid samples that were available, the concentrations below the detection limit were 10 of 16 samples for nelfinavir, 11 of 16 samples for M8, 1 of 3 samples for indinavir, 4 of 4 samples for ritonavir, and 0 of 1 samples for amprenavir. There were significant correlations between cord blood and maternal concentrations of nelfinavir and its metabolite M8. CONCLUSION: Placental transfer of the human immunodeficiency virus protease inhibitors is generally low; however, it may differ greatly according to the molecule.

Adult↗
PubMed2006

Bayesian network analysis of resistance pathways against HIV-1 protease inhibitors.

Interpretation of Human Immunodeficiency Virus 1 (HIV-1) genotypic drug resistance is still a major challenge in the follow-up of antiviral therapy in infected patients. Because of the high degree of HIV-1 natural variation, complex interactions and stochastic behaviour of evolution, the role of resistance mutations is in many cases not well understood. Using Bayesian network learning of HIV-1 sequence data from diverse subtypes (A, B, C, F and G), we could determine the specific role of many resistance mutations against the protease inhibitors (PIs) nelfinavir (NFV), indinavir (IDV), and saquinavir (SQV). Such networks visualize relationships between treatment, selection of resistance mutations and presence of polymorphisms in a graphical way. The analysis identified 30N, 88S, and 90M for nelfinavir, 90M for saquinavir, and 82A/T and 46I/L for indinavir as most probable major resistance mutations. Moreover we found striking similarities for the role of many mutations against all of these drugs. For example, for all three inhibitors, we found that the novel mutation 89I was minor and associated with mutations at positions 90 and 71. Bayesian network learning provides an autonomous method to gain insight in the role of resistance mutations and the influence of HIV-1 natural variation. We successfully applied the method to three protease inhibitors. The analysis shows differences with current knowledge especially concerning resistance development in several non-B subtypes.

Bayes Theorem↗
PubMed2000

In vitro metabolism of trazodone by CYP3A: inhibition by ketoconazole and human immunodeficiency viral protease inhibitors.

BACKGROUND: Pharmacologic treatment of emotional disorders in HIV-infected patients can be more easily optimized by understanding of potential interactions of psychotropic drugs with medications used to treat HIV infection and its sequelae. METHODS: Biotransformation of the antidepressant trazodone to its principal metabolite, meta-chlorophenylpiperazine (mCPP), was studied in vitro using human liver microsomes and heterologously expressed individual human cytochromes. Interactions of trazodone with the azole antifungal agent, ketoconazole, and with human immunodeficiency virus protease inhibitors (HIVPIs) were studied in the same system. RESULTS: Formation of mCPP from trazodone in liver microsomes had a mean (+/- SE) K(m) value of 163 (+/- 21) micromol/L. Ketoconazole, a relatively specific CYP3A inhibitor, impaired mCPP formation consistent with a competitive mechanism, having an inhibition constant (K(i)) of 0.12 (+/- 0.01) micromol/L. Among heterologously expressed human cytochromes, only CYP3A4 mediated formation of mCPP from trazodone; the K(m) was 180 micromol/L, consistent with the value in microsomes. The HIVPI ritonavir was a potent inhibitor of mCPP formation in liver microsomes (K(i) = 0.14 +/- 0.04 micromol/L). The HIVPI indinavir was also a strong inhibitor, whereas saquinavir and nelfinavir were weaker inhibitors. CONCLUSIONS: CYP3A-mediated clearance of trazodone is inhibited by ketoconazole, ritonavir and indinavir, and indicates the likelihood of pharmacokinetic interactions in vivo.

Antidepressive Agents, Second-Generation↗
PubMed1997

Determination of an in vivo metabolite of a human immunodeficiency virus protease-inhibitor in human plasma by high-performance liquid chromatography with tandem mass spectrometry.

A method for the determination of a metabolic of the human immunodeficiency virus protease inhibitor indinavir, in human plasma is described. Isolation of the analyte and the internal standard from plasma was achieved via liquid-liquid extraction with a mixture of isopropanol-chloroform (5:95, v/v). The analytes were chromatographed under reversed-phase conditions on a Waters Symmetry C, column. A Sciex API III+ tandem mass spectrometer equipped with a heated nebulizer was used as a detector and was operated in the positive ion mode. Multiple reaction monitoring using the precursor-->production combinations of m/z, 523.4-->273.4 and 512.4-->345.2 was used to quantify analyte and internal standard, respectively. The method was validated in the concentration range of 5-500 ng/ml plasma with adequate assay precision and accuracy. The assay was used to analyze samples collected during drug interaction studies of indinavir.

Antifungal Agents↗
PubMed2001

Naltrexone potentiates anti-HIV-1 activity of antiretroviral drugs in CD4+ lymphocyte cultures.

CD4(+) T lymphocytes are the primary cell target for human immunodeficiency virus-1 (HIV-1), and these cells are known to express opioid receptors. Due to the need for new treatment approaches to HIV-1 infection, we sought to determine whether the non-selective opioid receptor antagonist naltrexone would affect HIV-1 expression in CD4(+) lymphocyte cultures and whether naltrexone would alter the antiviral properties of zidovudine (AZT) or indinavir. Activated CD4(+) lymphocytes were infected with a monocytotropic or T-cell tropic HIV-1 isolate, and p24 antigen levels were measured in supernatants of drug-treated or untreated (control) cultures. While naltrexone alone did not affect HIV-1 expression, at a concentration of 10(-12)-10(-10) M naltrexone increased the antiviral activity of AZT and indinavir 2-3-fold. Similar findings with a kappa-opioid receptor (KOR) selective antagonist supported the possible involvement of KOR in naltrexone's potentiation of the antiretroviral drugs. The results of this in vitro study suggest that treatment of alcohol or opiate dependent HIV-1-infected patients with naltrexone is unlikely to interfere with the activity of antiretroviral drugs. Also, based upon naltrexone's safety profile and its synergistic activity in vitro, these findings suggest clinical trials should be considered of naltrexone as an adjunctive therapy of HIV-1 infection.

Anti-HIV Agents↗
PubMed1999

Effect of protease inhibitors on the sense of taste.

The purpose of this study was to investigate the taste properties of protease inhibitors which are essential components of drug regimes used to treat human immunodeficiency virus (HIV) infection. In this study, the taste properties of four protease inhibitors (indinavir, ritonavir, saquinavir, and nelfinavir) were investigated in unmedicated HIV-infected patients and healthy controls. Three of the four protease inhibitors (indinavir, ritonavir, and saquinavir) were found to be predominantly bitter (with additional qualities of medicinal, metallic, astringent, sour, and burning). Nelfinavir was found to be relatively tasteless. HIV-infected and uninfected control subjects detected protease inhibitors at similar concentrations, but HIV-infected subjects perceived suprathreshold concentrations as more bitter than controls. Detection thresholds ranged from 0.0061 mM for saquinavir in HIV-infected patients to 0.0702 mM for ritonavir in uninfected control subjects. Suprathreshold studies indicated that protease inhibitors modified the taste perception of a variety of other taste compounds. These results are consistent with clinical findings that protease inhibitors produce taste complaints that can impact patient compliance.

Adult↗
PubMed2004

Comparing the accumulation of active- and nonactive-site mutations in the HIV-1 protease.

Protease inhibitor resistance still poses one of the greatest challenges in treating HIV. To better design inhibitors able to target resistant proteases, a deeper understanding is needed of the effects of accumulating mutations and the contributions of active- and nonactive-site mutations to the resistance. We have engineered a series of variants containing the nonactive-site mutations M46I and I54V and the active-site mutation I84V. These mutations were added to a protease clone (V6) isolated from a pediatric patient on ritonavir therapy. This variant possessed the ritonavir-resistance-associated mutations in the active-site (V32I and V82A) and nonactive-site mutations (K20R, L33F, M36I, L63P, A71V, and L90M). The I84V mutation had the greatest effect on decreasing catalytic efficiency, 10-fold when compared to the pretherapy clone LAI. The decrease in catalytic efficiency was partially recovered by the addition of mutations M46I and I54V. The M46I and I54V were just as effective at decreasing inhibitor binding as the I84V mutation when compared to V6 and LAI. The V6(54/84) variant showed over 1000-fold decrease in inhibitor-binding strength to ritonavir, indinavir, and nelfinavir when compared to LAI and V6. Crystal-structure analysis of the V6(54/84) variant bound to ritonavir and indinavir shows structural changes in the 80's loops and active site, which lead to an enlarged binding cavity when compared to pretherapy structures in the Protein Data Bank. Structural changes are also seen in the 10's and 30's loops, which suggest possible changes in the dynamics of flap opening and closing.

Binding Sites↗
PubMed2000

Elucidation of distinct ligand binding sites for cytochrome P450 3A4.

Cytochrome P450 (P450) 3A4 is the most abundant human P450 enzyme and has broad selectivity for substrates. The enzyme can show marked catalytic regioselectivity and unusual patterns of homotropic and heterotropic cooperativity, for which several models have been proposed. Spectral titration studies indicated one binding site for the drug indinavir (M(r) 614), a known substrate and inhibitor. Several C-terminal aminated peptides, including the model morphiceptin (YPFP-NH(2)), bind with spectral changes indicative of Fe-NH(2) bonding. The binding of the YPFP-NH(2) N-terminal amine and the influence of C-terminal modification on binding argue that the entire molecule (M(r) 521) fits within P450 3A4. YPFP-NH(2) was not oxidized by P450 3A4 but blocked binding of the substrates testosterone and midazolam, with K(i) values similar to the spectral binding constant (K(s)) for YPFP-NH(2). YPFP-NH(2) inhibited the oxidations of several typical P450 substrates with K(i) values 10-fold greater than the K(s) for binding YPFP-NH(2) and its K(i) for inhibiting substrate binding. The n values for cooperativity of these oxidations were not altered by YPFP-NH(2). YPFP-NH(2) inhibited the oxidations of midazolam at two different positions (1'- and 4-) with 20-fold different K(i) values. The differences in the K(i) values for blocking the binding to ferric P450 3A4 and the oxidation of several substrates may be attributed to weaker binding of YPFP-NH(2) to ferrous P450 3A4 than to the ferric form. The ferrous protein can be considered a distinct form of the enzyme in binding and catalysis because many substrates (but not YPFP-NH(2)) facilitate reduction of the ferric to ferrous enzyme. Our results with these peptides are considered in the context of several proposed models. A P450 3A4 model based on these peptide studies contains at least two and probably three distinct ligand sites, with testosterone and alpha-naphthoflavone occupying distinct sites. Midazolam appears to be able to bind to P450 3A4 in two modes, one corresponding to the testosterone binding mode and one postulated to reflect binding in a third site, distinct from both testosterone and alpha-naphthoflavone. The work with indinavir and YPFP-NH(2) also argues that room should be present in P450 3A4 to bind more than one smaller ligand in the "testosterone" site, although no direct evidence for such binding exists. Although this work with peptides provides evidence for the existence of multiple ligand binding sites, the results cannot be used to indicate their juxtaposition, which may vary through the catalytic cycle.

Binding Sites↗
PubMed2001

In vitro metabolism and drug interaction potential of a new highly potent anti-cytomegalovirus molecule, CMV423 (2-chloro 3-pyridine 3-yl 5,6,7,8-tetrahydroindolizine I-carboxamide).

AIMS: To identify the enzymes involved in the metabolism of CMV423, a new anticytomegalovirus molecule, to evaluate its in vitro clearance and to investigate its potential involvement in drug/drug interactions that might occur in the clinic. METHODS: The enzymes involved in and the kinetics of CMV423 biotransformation were determined using pools of human liver subcellular fractions and heterologously expressed human cytochromes P450 (CYP) and FMO. The effect of CMV423 on CYP probe activities as well as on indinavir and AZT metabolism was determined, and 26 drugs were tested for their potential to inhibit or activate CMV423 metabolism. RESULTS: CMV423 was oxidized by CYP and not by FMO or cytosolic enzymes. The Km values for 8-hydroxylation to rac-RPR 127025, an active metabolite, and subsequent ketone formation by human liver microsomes were 44 +/- 13 microM and 47 +/- 11 microM, respectively, with corresponding Vmax/Km ratios of 14 and 4 microl min(-1) nmol(-1) P450. Inhibition with selective CYP inhibitors indicated that CYP1A2 was the main isoform involved, with some participation from CYP3A. Expressed human CYP1A1, 1A2, 2C9, 3A4 and 2C8 catalysed rac-RPR 127025 formation with Km values of < 10 microM, 50 +/- 21 microM, 55 +/- 19 microM, circa 282 +/- 61 microM and circa 1450 microM, respectively. CYP1B1, 2A6, 2B6, 2C19, 2D6, 2E1 or 3A5 did not catalyse the reaction to any detectable extent. CYP1A1 and 3A4 also catalysed ketone formation from rac-RPR 127025. In human liver microsomes, CMV423 at 1 and 10 microM inhibited CYP1A2 activity up to 31% and 63%, respectively, CYP3A4 activity up to 40% (10 microM) and CYP2C9 activity by 35% (1 and 10 microM). No effect was observed on CYP2A6, 2D6 and 2E1 activities. CMV423 had no effect on indinavir and AZT metabolism. Amongst 26 drugs tested, none inhibited CMV423 metabolism in vitro at therapeutic concentrations. CONCLUSIONS: CMV423 is mainly metabolized by CYP1A2 and 3A4. Its metabolism should not be saturable at the targeted therapeutic concentrations range (Cmax < 1 microM). CMV423 will probably affect CYP1A2 and 1A1 activities in vivo to some extent, but no other drug-drug interactions are expected.

Adolescent↗
PubMed1998

Effect of protease inhibitors on nucleoside analogue phosphorylation in vitro.

AIMS: Combination antiretroviral therapy for human immunodeficiency virus (HIV) infection now involves both nucleoside analogues and protease inhibitors. Since intracellular phosphorylation is essential for the activity of all the nucleoside analogues this study was designed to investigate interactions with protease inhibitors at the intracellular level which may alter antiviral efficacy. METHODS: PHA-stimulated PBMCs (3 x 10[6] cell/plate) and U937 cells (4 x 10[6] cells/plate) were incubated with either radiolabelled zidovudine (ZDV), stavudine (d4T), zalcitabine (ddC), lamivudine (3TC) or didanosine (ddI) in the presence and absence of the protease inhibitors, indinavir, ritonavir, and saquinavir (0.1-10 microM) for 24 h. Cells were extracted overnight prior to analysis by radiometric h.p.l.c. Intracellular phosphates were standardised to pmol per million cells. RESULTS: None of the three protease inhibitors tested had any significant effect on the intracellular phosphorylation of the five nucleoside analogues. It is particularly important to focus on the active triphosphate anabolites and data for control vs ritonavir (10 microM) incubations in U937 cells were as follows: ZDVTP, 0.19 +/- 0.02 vs 0.21 +/- 0.2 pmol/10(6) cells (mean +/- s.d.; n = 5); d4TTP, 0.30 +/- 0.13 vs 0.27 +/- 0.26; 3TCTP, 0.32 +/- 0.12 vs 0.26 +/- 0.19; ddCTP, 0.07 +/- 0.04 vs 0.06 +/- 0.02, ddATP, 0.014 +/- 0.003 vs 0.018 +/- 0.006 pmol/10(6) cells. CONCLUSIONS: The protease inhibitors, indinavir, ritonavir and saquinavir have no effect on the enzymes responsible for phosphorylation. Combining protease inhibitors and nucleoside analogues should not lead to any intracellular interactions in vivo.

Anti-HIV Agents↗
PubMed1999

Paronychia associated with antiretroviral therapy.

We report six HIV patients who developed painful periungual inflammation of several nails during treatment with the antiretroviral drugs indinavir and lamivudine. The lesions appeared 2-12 months after starting treatment. The occurrence of paronychia in HIV patients has recently been reported in two groups of patients receiving either indinavir or lamivudine. Dermatologists should be aware of this recently reported and probably not uncommon side-effect of antiretroviral treatment in order to avoid an invasive approach to the nail lesions.

Administration, Topical↗