Low incidence of acute rejection within 6 months of kidney transplantation in HIV-infected recipients treated with raltegravir: the Agence Nationale de Recherche sur le Sida et les Hépatites Virales (ANRS) 153 TREVE trial.

OBJECTIVES: High rates of clinical acute rejection after kidney transplantation have been reported in people living with HIV (PLHIV), probably as a consequence of drug interactions. We therefore investigated the incidence of acute rejection within 6 months of transplantation in HIV-infected recipients treated with a protease-inhibitor-free raltegravir-based regimen. METHODS: The Agence Nationale de Recherche sur le Sida et les Hépatites Virales (ANRS) 153 TREVE (NCT01453192) study was a prospective multicentre single-arm trial in adult PLHIV awaiting kidney transplantation, with viral load < 50 HIV-1 RNA copies/mL, CD4 T-cell count > 200 cells/µL, and HIV-1 strains sensitive to raltegravir, aiming to demonstrate 6-month clinical acute rejection rates < 30%. Time to transplantation was compared with that for uninfected subjects matched for age, sex and registration date. RESULTS: In total, 61 participants were enrolled in the study, and 26 underwent kidney transplantation. Two participants experienced clinical acute rejection, corresponding to an estimated clinical acute rejection rate of 8% [95% confidence interval (CI) 2-24%] at 6 and 12 months post-transplantation. HIV infection remained under control in all but one participant, who temporarily stopped antiretroviral treatment. Median time to transplantation was longer in PLHIV than in controls (4.3 versus 2.8 years, respectively; P = 0.002) and was not influenced by blood group. CONCLUSIONS: Acute rejection rates were low after kidney transplantation in PLHIV treated with a raltegravir-based regimen. However, PLHIV have poorer access to transplantation than HIV-uninfected individuals after registration on the waiting list.

Worsening pneumonitis due to a pharmacokinetic drug-drug interaction between everolimus and voriconazole in a renal transplant patient.

WHAT IS KNOWN AND OBJECTIVE: Azole antifungals, prescribed prophylactically to avoid severe infections in immunosuppressed organ transplant recipients, can interact with drug substrates of CYP3A4. We report serious adverse effects due to interaction between orally administered voriconazole and everolimus in a renal transplant recipient. CASE DESCRIPTION: Despite reduction of the dose of everolimus by a third, the blood trough concentration of everolimus increased considerably in a kidney transplant recipient upon oral administration of voriconazole. Everolimus was then discontinued. Pneumonia secondary to pulmonary aspergillosis worsened, possibly due to the excessive immunosuppression. WHAT IS NEW AND CONCLUSION: Orally administered voriconazole inhibits intestinal and hepatic cytochrome P450-3A4 activity and thereby reduces everolimus metabolism. An 80% decrease in dose or discontinuation of everolimus is required when concomitant voriconazole is introduced. Daily blood monitoring of everolimus is warranted until a steady state of concentrations is reached.

Pharmacokinetics of rifampin and isoniazid in tuberculosis-HIV-coinfected patients receiving nevirapine- or efavirenz-based antiretroviral treatment.

This is a substudy of the Agence Nationale de Recherches sur le Sida et les Hépatites Virales (ANRS) Comparison of Nevirapine and Efavirenz for the Treatment of HIV-TB Co-infected Patients (ANRS 12146-CARINEMO) trial, which assessed the pharmacokinetics of rifampin or isoniazid with or without the coadministration of nonnucleoside reverse transcriptase inhibitor-based HIV antiretroviral therapy in HIV-tuberculosis-coinfected patients in Mozambique. Thirty-eight patients on antituberculosis therapy based on rifampin and isoniazid participated in the substudy (57.9% males; median age, 33 years; median weight, 51.9 kg; median CD4(+) T cell count, 104 cells/µl; median HIV-1 RNA load, 5.5 log copies/ml). The daily doses of rifampin and isoniazid were 10 and 5 mg/kg of body weight, respectively. Twenty-one patients received 200 mg of nevirapine twice a day (b.i.d.), and 17 patients received 600 mg of efavirenz once a day (q.d.) in combination with lamivudine and stavudine from day 1 until the end of the study. Blood samples were collected at regular time-dosing intervals after morning administration of a fixed-dose combination of rifampin and isoniazid. When rifampin was administered alone, the median maximum concentration of drug in serum (Cmax) and the area under the concentration-time curve (AUC) at steady state were 6.59 mg/liter (range, 2.70 to 14.07 mg/liter) and 27.69 mg · h/liter (range, 11.41 to 109.75 mg · h/liter), respectively. Concentrations remained unchanged when rifampin was coadministered with nevirapine or efavirenz. When isoniazid was administered alone, the median isoniazid Cmax and AUC at steady state were 5.08 mg/liter (range, 1.26 to 11.51 mg/liter) and 20.92 mg · h/liter (range, 7.73 to 56.95 mg · h/liter), respectively. Concentrations remained unchanged when isoniazid was coadministered with nevirapine; however, a 29% decrease in the isoniazid AUC was observed when isoniazid was combined with efavirenz. The pharmacokinetic parameters of rifampin and isoniazid when coadministered with nevirapine or efavirenz were not altered to a clinically significant extent in these severely immunosuppressed HIV-infected patients. Patients experienced favorable clinical outcomes. (This study has been registered at ClinicalTrials.gov under registration no. NCT00495326.).

Long-term efficacy of darunavir/ritonavir monotherapy in patients with HIV-1 viral suppression: week 96 results from the MONOI ANRS 136 study.

OBJECTIVES: Long-term results at week 96 are needed to evaluate the capacity of the darunavir/ritonavir monotherapy strategy to maintain a sustained control of the HIV-1 viral load. METHODS: MONOI is a prospective, open-label, non-inferiority, randomized, 96 week trial comparing darunavir/ritonavir monotherapy versus a darunavir/ritonavir triple-therapy strategy to maintain HIV-1 viral load suppression in HIV-1-infected patients. CLINICAL TRIAL REGISTRATION: NCT00412551. RESULTS: From 225 randomized patients, 219 patients reached the 48 week follow-up and 211 reached the 96 week follow-up (106 patients in the darunavir monotherapy arm and 105 in the darunavir triple-therapy arm). Baseline characteristics were well balanced between the two treatment groups. At week 96, in intent-to-treat analysis, 91/103 patients (88%, 95% CI 81-94) allocated to the darunavir/ritonavir monotherapy arm and 87/104 patients (84%, 95% CI 75-90) allocated to the darunavir triple-therapy arm achieved an HIV-1 viral load <50 copies/mL, with no statistical difference between the two groups. Throughout the 96 week follow-up, 66/112 patients (59%, 95% CI 49-68) and 79/113 patients (70%, 95% CI 61-78) consistently had HIV-1 RNA <50 copies/mL with darunavir/ritonavir monotherapy and darunavir/ritonavir triple therapy, respectively. CONCLUSIONS: The MONOI study establishes darunavir/ritonavir monotherapy as durable and efficacious for maintaining virological suppression in HIV-1 patients. Darunavir/ritonavir monotherapy should be considered as a (tailored) treatment option for standard triple-therapy patients who have had a substantial period of viral suppression.

Influence of alpha-1 glycoprotein acid concentrations and variants on atazanavir pharmacokinetics in HIV-infected patients included in the ANRS 107 trial.

Atazanavir is an HIV-1 protease inhibitor with high protein binding in human plasma. The objectives were first to determine the in vitro binding characteristics of atazanavir and second to evaluate whether plasma protein binding to albumin and alpha-1 glycoprotein acid (AAG) influences the pharmacokinetics of atazanavir in HIV-infected patients. For the in vitro study, atazanavir protein binding characteristics were determined in AAG- and albumin-containing purified solutions. Atazanavir was found to bind AAG on a high-affinity saturable site (association constant, 4.61x10(5) liters/mol) and albumin on a low-affinity nonsaturable site. For the in vivo study, blood samples from 51 patients included in trial ANRS 107--Puzzle 2 were drawn prior to drug intake at week 6. For 10 patients included in the pharmacokinetic substudy, five additional blood samples were collected during one dosing interval at week 6. Atazanavir concentrations were assayed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Albumin concentrations, AAG concentrations, and phenotypes were also measured in these patients. Concentrations of atazanavir were modeled using a population approach. A one-compartment model with first-order absorption and elimination best described atazanavir pharmacokinetics. Atazanavir pharmacokinetic parameters and their interindividual variabilities were as follows: absorption rate constant (ka), 0.73 h(-1) (139.3%); apparent clearance (CL/F), 13.3 liters/h (26.7%); and apparent volume of distribution (V/F), 79.7 liters (27.0%). Atazanavir CL/F decreased significantly when alanine aminotransferase and/or AAG levels increased (P<0.01). The ORM1*S phenotype also significantly increased atazanavir V/F (P<0.05). These in vivo results indicate that atazanavir pharmacokinetics is moderately influenced by its protein binding, especially to AAG, without expected clinical consequences.

High rate of virologic suppression with raltegravir plus etravirine and darunavir/ritonavir among treatment-experienced patients infected with multidrug-resistant HIV: results of the ANRS 139 TRIO trial.

BACKGROUND: The introduction of 2 or 3 fully active drugs in human immunodeficiency virus (HIV)-infected patients receiving failing antiretroviral therapy is a key determinant of subsequent treatment efficacy. The aim of this study was to assess the safety and efficacy of a regimen containing raltegravir, etravirine, and darunavir/ritonavir for treatment-experienced patients infected with multidrug-resistant HIV. METHODS: Patients enrolled in this phase II, noncomparative, multicenter trial were naive to the investigational drugs and had plasma HIV RNA levels >1000 copies/mL, a history of virologic failure while receiving nonnucleoside reverse-transcriptase inhibitors (NNRTI), > or =3 primary protease inhibitor and nucleoside reverse transcriptase inhibitor (NRTI) mutations, and < or =3 darunavir and NNRTI mutations. The primary end point was the proportion of patients with plasma HIV RNA levels <50 copies/mL at 24 weeks. RESULTS: A total of 103 patients enrolled in the study. At baseline, genotypic resistance profiles showed a median of 4 primary protease inhibitor mutations, 1 NNRTI mutation, and 6 NRTI mutations. In addition to the investigational drugs, 90 patients (87%) received optimized background therapy that included NRTIs (86 patients) or enfuvirtide (12 patients). At week 24, 90% of patients (95% confidence interval, 85%-96%) had an HIV RNA level <50 copies/mL. At week 48, 86% (95% confidence interval, 80%-93%) had an HIV RNA level <50 copies/mL. The median CD4 cell count increase was 108 cells/mm(3). Grade 3 or 4 clinical adverse events were reported in 15 patients (14.6%). Only 1 patient discontinued the investigational antiretroviral regimen, because of an adverse event. CONCLUSION: In patients infected with multidrug-resistant virus who have few remaining treatment options, the combination of raltegravir, etravirine, and darunavir/ritonavir is well tolerated and is associated with a rate of virologic suppression similar to that expected in treatment-naive patients.

Pharmacokinetic studies of nifedipine tablet. Correlation with antihypertensive effects.

A tablet form of nifedipine was given to eight hypertensive hospitalized men (Stage I or II WHO, 45 +/- 10 years old). After an initial placebo test, 20, 40, and 60 mg of nifedipine were given at 8.00 a.m. in random order at 72-hour intervals in a single administration double-blind crossover study. Blood pressure and heart rate were measured twice by the same observer every 20 minutes from 7.00 a.m. to 8.00 a.m. and then hourly until 8.00 p.m., first with the patients recumbent and again after 1 minute of standing. Plasma nifedipine levels were assayed in samples drawn hourly from 8.00 a.m. to noon, every 2 hours from noon to 8.00 p.m., and at 24 and 48 hours after drug ingestion. The three doses all lowered blood pressure significantly. The reduction during recumbency was significantly larger (-18%) and lasted longer (12 hours) after 60 mg than after 20 mg (-11% at 7 hours). The three doses caused similar increases in heart rate (+29% to +38%), the maximum occurring at the second hour and lasting for 5 hours. The peak plasma concentrations and areas under the plasma concentration time curve were dose-dependent; kinetics were linear between 20 and 60 mg, and the half-life of nifedipine tablets was close to 10 hours. The decrease in mean arterial blood pressure correlated strongly with plasma nifedipine levels (r = 0.61; n = 190; p less than 0.001). Four patients experienced mild side effects (headaches, flushes, drowsiness, or weakness). The tablet form of nifedipine had a potent antihypertensive action that lasted longer than that of the capsule formulation.

Zidovudine disposition in patients with severe renal impairment: influence of hemodialysis.

Pharmacokinetics of zidovudine (azidothymidine, AZT) was investigated after oral administration (200 mg) in 25 HIV seronegative subjects: 14 patients with severe renal impairment (creatinine clearance 6 to 31 ml/min), five hemodialyzed anuric patients, and six healthy subjects. Plasma and urine concentrations of zidovudine and its glucuronidated metabolite (GAZT) were measured simultaneously by HPLC assay. In healthy subjects, GAZT concentrations were higher than those of AZT; AUC values were 23.7 +/- 1.9 and 5.2 +/- 0.6 mumol.hr/L, respectively. Formation of GAZT rate-limits its elimination: GAZT half-life (t 1/2) parallels that of AZT, which is around 1 hour. In uremic patients, AZT concentrations were moderately increased (AUC = 11.7 +/- 1.1 mumol.hr/L), whereas t 1/2 and mean residence time (MRT) remain unchanged despite the decreased renal clearance (16 +/- 2 versus 220 +/- 58 ml/min) and decreased urinary excretion (1.6 +/- 0.3 versus 8.1 +/- 1.0% of the dose). In contrast, GAZT concentrations are markedly increased (AUC = 402.9 +/- 88.6 mumol.hr/L). As a consequence of the decreased renal clearance (27 +/- 3 versus 331 +/- 42 ml/min), elimination is the rate-limiting step and t 1/2 is increased (8 +/- 2 versus 0.9 +/- 0.1 hr). Contribution of a 4-hour hemodialysis session to AZT elimination appears to be negligible, whereas elimination of GAZT is enhanced. On the sole basis of AZT pharmacokinetic data, no particular dose adjustment appears to be necessary in patients who have severe renal impairment (creatinine clearance between 10 and 30 ml/min). However, high levels of GAZT should be anticipated with the usual dosage regimen.

Pharmacokinetics of ornidazole in patients with acute viral hepatitis, alcoholic cirrhosis, and extrahepatic cholestasis.

Pharmacokinetics of ornidazole, a nitroimidazole derivative, was investigated after intravenous injection in 3 groups of 10 patients with different hepatic diseases: hepatitis, noncholestatic cirrhosis and extrahepatic cholestasis. Plasma concentrations of ornidazole and its two major hydroxylated metabolites, M1 [alpha-(chloromethyl)-2-hydroxymethyl-5-nitroimidazole-1-ethanol] and M4 [3-(2-methyl-5-nitroimidazole 1-yl)-1,2-propane diol] were measured by HPLC assay. As a consequence of a decreased clearance (26% to 48%), the half-life and MRT are increased in all patients by 19% to 38% when compared with healthy volunteers. No clear difference could be established between the different groups. The volume of distribution remains the same in all patients and controls except those suffering from cancer. As previously shown in patients with severe liver cirrhosis, both metabolites accumulate in plasma as a result of decreased elimination; formation is no longer the rate-limiting step of their kinetics. This metabolite accumulation is in part due to decreased biliary excretion and to hepatocellular failure.

Pharmacokinetics of ornidazole in patients with severe liver cirrhosis.

Pharmacokinetics of ornidazole, a nitroimidazole derivative, was studied after intravenous injection in 10 patients with severe alcoholic cirrhosis and 10 healthy volunteers. Plasma concentrations of ornidazole and its two major hydroxylated metabolites, M1 (alpha-(chloromethyl)-2-hydroxymethyl-5-nitroimidazole-1-ethanol) and M4 (3-(2-methyl-5-nitroimidazole 1-yl) 1,2 propane diol), were measured by HPLC. The t1/2 of ornidazole was 14.1 +/- 0.5 hours for normal subjects and 21.9 +/- 2.9 hours for patients with cirrhosis. Mean plasma clearance was 50.6 +/- 2.1 ml/min in control subjects and 34.9 +/- 4.9 ml/min in patients, whereas apparent V SS was not modified in hepatic insufficiency. In healthy volunteers, M1 and M4 levels are well below levels of the parent drug; in cirrhosis both metabolites accumulate in plasma as a result of decreased elimination. Hepatic cirrhosis prolongs ornidazole elimination, and to avoid cumulation the interval between repeated doses could be doubled.

Pharmacokinetics of zidovudine in patients with liver cirrhosis.

The pharmacokinetics of zidovudine (azidothymidine, AZT) was investigated after oral administration (200 mg) in 14 human immunodeficiency virus seronegative patients with liver cirrhosis. They were divided in three groups according to the severity of the liver disease quantitated by the Child-Pugh score. Plasma and urine concentrations of zidovudine and its glucuronidated metabolite (GAZT) were measured simultaneously by HPLC assay. Findings were compared with those previously measured in six healthy volunteers. As a consequence of a marked drop in oral clearance (10 +/- 4 versus 38 +/- 15 ml/min/kg), zidovudine concentrations, half-life, and mean residence time were increased in patients with cirrhosis. No difference could be established between the three groups. The reason for such a decrease in oral clearance of zidovudine was the reduction in the GAZT formation clearance (236 +/- 73 versus 1540 +/- 540 ml/min); this led to a decrease in the AUC ratio of GAZT and zidovudine (1.3 +/- 0.6 versus 4.6 +/- 0.7), which was directly related to the severity of the cirrhosis. In patients, as in volunteers, formation of GAZT rate limits its elimination. To avoid important cumulation of zidovudine after repeated dosing in patients with acquired immunodeficiency syndrome who have hepatic impairment, a dosage adjustment could be proposed.

Toxicologic and pharmacokinetic analysis of intravitreal injections of foscarnet, either alone or in combination with ganciclovir.

PURPOSE: The retinal toxicity of single and repeated intravitreal injections of foscarnet was investigated. In addition, the effects of a combination of foscarnet and ganciclovir were studied, and a pharmacokinetic study to determine the ocular pharmacokinetics of foscarnet after intravitreal injection was carried out. METHODS: Forty rabbits (both albino and pigmented) were used in this study. The electroretinographic (ERG) a-waves and b-waves and oscillatory potentials (OP) were used as as indicators of retinal toxicity. Potential toxicity was also assessed by ophthalmoscopy and histologic studies (light and electron microscopy). RESULTS: The a-wave and b-wave were not deteriorated with 2.4 mg foscarnet after single or repeated injections. The OP remained unchanged. There was no ERG change after intravitreal injection of a combination of both drugs. No evidence of retinal toxicity was observed by indirect ophthalmoscopy in any case. Light and electron microscopy on semithin sections of retina failed to demonstrate any adverse effects, and showed normal organization and cytoarchitecture of all the layers of the retina without evidence of cytopathology. The ocular pharmacokinetics of foscarnet determined by noncompartmental analysis showed a 34-hour terminal elimination half-life and an apparent volume of distribution of 1.9 ml. CONCLUSIONS: Based on these results, high doses of foscarnet were not judged toxic to the rabbit retina, with single or repeated injections. Moreover, concomitant injection of the two drugs did not induce any retinal toxicity. These findings suggest that when systemic treatment is to be stopped in patients with AIDS for toxic side effects, either ganciclovir or foscarnet may be used intravitreally as an alternative. Because a combination of the two drugs has been shown to be synergistic, both ganciclovir and foscarnet might be simultaneously injected into the vitreous cavity to block progression of cytomegalovirus retinitis.

Pharmacokinetic optimisation of asthma treatment.

Asthma is generally managed with bronchodilator therapy and/or anti-inflammatory drugs. Guidelines now advocate selection of drugs and pharmaceutical formulations (long-acting vs short-acting, inhaled vs systemic) on the basis of disease severity. Theophylline has a narrow therapeutic margin. Clearance is highly variable and plasma concentrations should be monitored to avoid the occurrence of plasma concentration-related adverse effects. The rate of absorption of theophylline differs depending on the sustained release formulation administered. Some products do not provide sufficient plasma drug concentrations for therapeutic efficacy over a 12-hour period, particularly in patients with high clearance rates (e.g. children and patients who smoke). Administration of drugs via inhalation offers several advantages over systemic routes of administration (e.g. adverse effects are decreased). Inhalation is now advocated as first-line therapy. Aerosol medications available for the treatment of asthma are beta 2-agonist (including the newer long-acting agents such as salmeterol), corticosteroids, anticholinergic drugs, sodium cromoglycate (cromolyn sodium) and nedocromil. To reach the airways, aerosolised particles should be 1 to 5 microns in diameter. Particles of this size can be produced by nebuliser for continuous administration or by metered-dose inhaler and drug powder inhaler for unit dose medication. For efficient use of the metered-dose inhaler, slow inhalation and actuation must be coordinated. However, efficacy and convenience can be improved when spacer devices are used. Furthermore, spacer devices lessen the oropharyngeal adverse effects of inhaled corticosteroids. Dry powder inhalers are more easily used by children and elderly patients than metered-dose inhalers. Regardless of the device used, a maximum of 10% of the inhaled dose reaches the airways. The rest of the dose is swallowed and absorbed through the gastrointestinal tract. Most inhaled drugs have low oral bioavailability, either because of a high first-pass metabolism (beta 2-agonists and glucocorticoids) or because of lack of absorption (sodium cromoglycate). Sulphation of beta 2-agonists occurs in the wall of the gastrointestinal tract and extensive metabolism of inhaled corticosteroids occurs in the liver. Low bioavailability of the swallowed fraction contributes to reduced adverse effects. The pharmacokinetic properties of an inhaled drug are of interest. The fraction of the dose absorbed through the lung has the same disposition characteristics as an intravenous dose, and the swallowed fraction has the same disposition as an orally administered dose. However, for many drugs, pharmacokinetic data after inhalation are limited and cannot be used as a criteria for selection of therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug interactions with antiviral drugs.

Antiviral drug interactions are a particular problem among immuno-compromised patients because these patients are often receiving multiple different drugs, i.e. antiretroviral drugs and drugs effective against herpesvirus. The combination of zidovudine and other antiretroviral drugs with different adverse event profiles, such as didanosine, zalcitabine and lamivudine, appears to be well tolerated and no relevant pharmacokinetic interactions have been detected. The adverse effects of didanosine and zalcitabine (i.e. peripheral neuropathy and pancreatitis) should be taken into account when administering these drugs with other drugs with the same tolerability profile. Coadministration of zidovudine and ganciclovir should be avoided because of the high rate of haematological intolerance. In contrast, zidovudine and foscarnet have synergistic effect and no pharmacokinetic interaction has been detected. No major change in zidovudine pharmacokinetics was seen when the drug was combined with aciclovir, famciclovir or interferons. However, concomitant use of zidovudine and ribavirin is not advised. Although no pharmacokinetic interaction was documented when didanosine was first administered with intravenous ganciclovir, recent studies have shown that concentration of didanosine are increased by 50% or more when coadministered with intravenous or oral ganciclovir. The mechanism of this interaction has not been elucidated. Lack of pharmacokinetic interaction was demonstrated between foscarnet and didanosine or ganciclovir. Clinical trials have shown that zidovudine can be administered safely with paracetamol (acetaminophen), nonsteroidal anti-inflammatory drugs, oxazepam or codeine. Inhibition of zidovudine glucuronidation has been demonstrated with fluconazole, atovaquone, valproic acid (valproate sodium), methadone, probenecid and inosine pranobex; however, the clinical consequences of this have not been fully investigated. No interaction has been demonstrated with didanosine per se but care should be taken of interaction with the high pH buffer included in the tablet formulation. Drugs that need an acidic pH for absorption (ketoconazole, itraconazole but not fluconazole, dapsone, pyrimethamine) or those that can be chelated by the ions of the buffer (quinolones and tetracyclines) should be administered 2 hours before or 6 hours after didanosine. Very few interaction studies have been undertaken with other antiviral drugs. Coadministration of zalcitabine with the antacid 'Maalox' results in a reduction of its absorption. Dapsone does not influence the disposition of zalcitabine. Cotrimoxazole (trimethoprim-sulfamethoxazole) causes an increase in lamivudine concentrations by 43%. Saquinavir, delavirdine and atevirdine appeared to be metabolised by cytochrome P450 and interactions with enzyme inducers or inhibitors could be anticipated. Some studies showed that interferons can reduce drug metabolism but only a few studies have evaluated the pathways involved. Further studies are required to better understand the clinical consequences of drug interactions with antiviral drugs. Drug-drug interactions should be considered in addition to individual drug clinical benefits and safety profiles.

The effect of respiratory disorders on clinical pharmacokinetic variables.

Respiratory disorders induce several pathophysiological changes involving gas exchange and acid-base balance, regional haemodynamics, and alterations of the alveolocapillary membrane. The consequences for the absorption, distribution and elimination of drugs are evaluated. Drug absorption after inhalation is not significantly impaired in patients. With drugs administered by this route, an average of 10% of the dose reaches the lungs. It is not completely clear whether changes in pulmonary endothelium in respiratory failure enhance lung absorption. The effects of changes in blood pH on plasma protein binding and volume of distribution are discussed, but relevant data are not available to explain the distribution changes observed in acutely ill patients. Lung diffusion of some antimicrobial agents is enhanced in patients with pulmonary infections. Decreased cardiac output and hepatic blood flow in patients under mechanical ventilation cause an increase in the plasma concentration of drugs with a high hepatic extraction ratio, such as lidocaine (lignocaine). On a theoretical basis, hypoxia should lead to decreased biotransformation of drugs with a low hepatic extraction ratio, but in vivo data with phenazone (antipyrine) or theophylline are conflicting. The effects of disease on the lung clearance of drugs are discussed but clinically relevant data are lacking. The pharmacokinetics of drugs in patients with asthma or chronic obstructive pulmonary disease are reviewed. Stable asthma and chronic obstructive pulmonary disease do not appear to affect the disposition of theophylline or beta 2-agonists such as salbutamol (albuterol) or terbutaline. Important variations in theophylline pharmacokinetics have been reported in critically ill patients, the causes of which are more likely to be linked to the poor condition of the patients than to a direct effect of hypoxia or hypercapnia. Little is known regarding the pharmacokinetics of cromoglycate, ipratropium, corticoids or antimicrobial agents in pulmonary disease. In patients under mechanical ventilation, the half-life of midazolam, a new benzodiazepine used as a sedative, has been found to be lengthened but the underlying mechanism is not well understood. Pulmonary absorption of pentamidine was found to be increased in patients under mechanical ventilation. Pharmacokinetic impairment does occur in patients with severe pulmonary disease but more work is needed to understand the exact mechanisms and to propose proper dosage regimens.

Disposition of fleroxacin, a new trifluoroquinolone, and its metabolites. Pharmacokinetics in elderly patients.

The pharmacokinetics of fleroxacin and its main metabolites, N-demethyl-fleroxacin and N-oxide-fleroxacin, were studied in 12 elderly patients aged 63 to 88 years. Plasma and urine samples collected at different times after drug administration were analysed by a specific reverse phase high performance liquid chromatography (HPLC) method. The peak plasma concentration (Cmax) of fleroxacin was 15.6 +/- 1.6 mg/L, time to Cmax (tmax) was about 3h, elimination half-life (t1/2) was 16 +/- 1h and the percentage of unchanged fleroxacin excreted in urine was 39 +/- 3% of the dose. The plasma concentrations of metabolites were very low and accounted for no more than 4% of the concentration of unchanged fleroxacin. Plasma parameters were mainly correlated with age and weight; urinary parameters were correlated with creatinine clearance. Compared with results in younger normal patients, no significant change in the t1/2 of fleroxacin or metabolites was observed. Assuming that the bioavailability (f) is complete, the apparent volume of distribution (Vd/f) was lower in elderly (0.9 +/- 0.1 L/kg) than in younger patients (1.3 +/- 0.1 L/kg) and a 2-fold decrease in apparent total clearance (CL/f) was noted (2.58 +/- 0.42 vs 4.86 +/- 0.72 L/h); plasma concentrations were consequently higher in elderly patients. Compared with patients with renal failure, the pharmacokinetics of fleroxacin and metabolites in the elderly were similar to those of patients with mild to moderate renal insufficiency. On the basis of the findings of this single dose study, no major dosage adjustments are needed for patients of this age range except for those with creatinine clearance less than 30 ml/min.

Disposition of fleroxacin, a new trifluoroquinolone, and its metabolites. Pharmacokinetics in renal failure and influence of haemodialysis.

The pharmacokinetics of fleroxacin and its metabolites following a single oral dose of fleroxacin 400mg were examined in 6 healthy subjects and 24 patients with various degrees of renal insufficiency. Plasma and urine samples, collected at various times after administration, were assayed by high performance liquid chromatography (HPLC). In healthy subjects, Cmax was 6.8 +/- 0.7 mg/L; tmax = about 1h, t1/2 = 14 +/- 2h, total clearance = 4.86 +/- 0.72 L/h and the percentage of unchanged fleroxacin excreted in urine in 48 hours was 48 +/- 4% (HPLC). Plasma concentrations of metabolites were very low and accounted for no more than 5% of the levels of unchanged fleroxacin. In uraemic patients Cmax did not change, whatever the degree of renal failure; tmax was increased in patients with a glomerular filtration rate below 0.6 L/h, and Vd/f was independent of the severity of renal failure. These data suggest that bioavailability of the drug is unchanged. In uraemic patients t1/2 was prolonged and AUC multiplied by a factor of 2 to 3. A linear relationship was found between total and renal clearances of fleroxacin and creatinine clearance. Accumulation of N-demethyl-fleroxacin and N-oxide-fleroxacin was very high in uraemic patients, due to slow formation of these metabolites and decreased urinary elimination. Dialysance of fleroxacin and of its metabolites was approximately 3.6 to 4.8 L/h. These findings suggest that fleroxacin dosage may need to be reduced in patients with severe renal disease; in haemodialysed patients, treated every 2 days, a single dose of fleroxacin 400mg is recommended at the end of each dialysis session.

In vitro effects of tacrolimus on human cytochrome P450.

Tacrolimus, a potent immunosuppressive drug, is known to be metabolized predominantly in the liver by cytochrome P450 3A (CYP3A). In order to determine the potential of tacrolimus to inhibit the metabolism of other drugs, we have investigated its inhibitory effects on specific cytochrome reactions. Specific substrates for the seven cytochromes (CYPs) 1A2, 2A6, 2C9, 2C19, 2D6, 2E1 and 3A4/5 were incubated with human hepatic microsome preparations with or without specific inhibitors or tacrolimus and the metabolites were detected by high-pressure liquid chromatography (HPLC) or fluorimetric methods. All the specific inhibitors reduced or abolished the specific CYP activity. Tacrolimus had no effect on any CYP at concentrations below 1 microM, while at higher concentrations it had a mild inhibitory effect on CYP3A4 and 3A5. These observations suggest that tacrolimus is unlikely to potentiate the effect of coadministered drugs through inhibition of their metabolism in the liver.

Carbon-13 nuclear magnetic resonance studies of spironolactone and several related steroids.

The 13C chemical shifts for all the carbon atoms is spironolactone have been assigned. Assignments for nine additional steroids which include the C-7 beta isomer of spironolactone, its C-7 thiol hydrolysis product, the 7 alpha-thioacetate derivative of testosterone and its thiol hydrolysis product are also reported.

Cimetidine does not alter sparfloxacin pharmacokinetics.

The interaction between cimetidine and sparfloxacin was studied in 10 healthy volunteers who received a single oral dose of 400 mg sparfloxacin on the third day of an 8 day cimetidine (400 mg t.i.d.) or placebo randomly assigned treatment. No statistically significant differences were observed in the pharmacokinetic parameters (Cmax-AUC-T1/2-urinary excretion and metabolic ratio) of sparfloxacin following the 2 treatment. Cimetidine does not affect absorption, metabolism or urinary excretion of sparfloxacin; consequently, patients exposed to this drug combination are not at risk.