Fleroxacin pharmacokinetics in patients with liver cirrhosis

SARS-CoV-2 entry inhibitors by dual targeting TMPRSS2 and ACE2: An in silico drug repurposing study

The coronavirus disease (COVID-19) is spreading between human populations mainly through nasal droplets. Currently, the vaccines have great hope, but it takes years for testing its efficacy in human. As there is no specific drug treatment available for COVID-19 pandemic, we explored in silico repurposing of drugs with dual inhibition properties by targeting transmembrane serine protease 2 (TMPRSS2) and human angiotensin-converting enzyme 2 (ACE2) from FDA-approved drugs. The TMPRSS2 and ACE2 dual inhibitors in COVID-19 would be a novel antiviral class of drugs called “entry inhibitors.” For this purpose, approximately 2800 US-FDA approved drugs were docked using a virtual docking tool with the targets TMPRSS2 and ACE2. The best-fit drugs were selected as per docking scores and visual outcomes. Later on, drugs were selected on the basis of molecular dynamics simulations. The drugs alvimopan, arbekacin, dequalinum, fleroxacin, lopinavir, and valrubicin were shortlisted by visual analysis and molecular dynamics simulations. Among these, lopinavir and valrubicin were found to be superior in terms of dual inhibition. Thus, lopinavir and valrubicin have the potential of dual-target inhibition whereby preventing SARS-CoV-2 entry to the host. For repurposing of these drugs, further screening in vitro and in vivo would help in exploring clinically.

Drug administration in chronic liver disease

Cirrhosis encompasses a range of pathophysiological changes that may alter drug disposition. Drugs that are dependent primarily on the liver for their systemic clearance are more likely to be subject to reduced elimination and subsequent accumulation. Drug accumulation may lead to excessive plasma drug concentrations and adverse effects, if the adverse effects of the drug are concentration-dependent. The effects of hepatic insufficiency on the pharmacokinetics of drugs are not consistent or predictable. Furthermore, the influence of hepatic disease on the disposition of various drugs can vary, even though those drugs may share the same apparent metabolic pathway. Problems in forecasting drug kinetic behaviour are further enhanced by the additional impairment of kidney function (frequently encountered in patients with advanced liver disease) and by the unpredictability of the glomerular filtration rate using customary methods in patients with cirrhosis. Accordingly, dosages are generally adapted empirically, with the help of serum drug concentrations, when applicable. However, drugs eliminated predominantly by hepatic metabolism are not among those most commonly inducing adverse drug reactions or causing severe complications in patients with cirrhosis. Electrolyte disturbances and the hepatorenal syndrome produced by furosemide (frusemide)-the disposition of which is not substantially modified in liver disease-appear to be the most frequent adverse drug reactions in patients with liver disease. Furthermore, clinically significant alterations in the action of medications at concentrations generally considered to be in the normal therapeutic range are not uncommon. Tissue responsiveness to the pharmacological action of some drugs may be modified, as evidenced by the increased susceptibility of the brain in patients with cirrhosis to the action of many psychoactive agents. Another example is the greater susceptibility of such patients to the nephrotoxic potential of aminogly-cosides, which should not be used in this patient group. Drugs may also interfere with adaptive physiological processes induced by liver disease. ACE inhibitors and nonsteroidal anti-inflammatory drugs counteract the enhanced activity of the renin-angiotensin system in advanced liver disease, thereby generating a high risk of excessive hypotension or acute renal failure, respectively. These drugs are best avoided in patients with cirrhosis. Finally, there may be pharmacological effects that overlap with some pathophysiological modifications related to the process of liver disease, such as increased portal pressure produced by some calcium antagonists, or hypoprothrombinaemia related to the inhibition of synthesis of vitamin K-dependent clotting factors by some beta-lactam antibacterials (especially moxalactam and cefamandole). Accordingly, the use of these drugs should be avoided in advanced liver disease. It is noteworthy that reduced drug metabolism in patients with liver disease does not seem to have a significant impact on the frequency of hepatotoxicity. Special caution should be exercised, however, in patients with alcoholic liver disease because excessive alcohol intake may potentiate the hepatotoxic effect of paracetamol (acetaminophen).

Clinical pharmacokinetic and pharmacodynamic considerations in patients with liver disease. An update

The effects of liver disease on pharmacokinetics and pharmacodynamics are highly variable, and difficult to predict as the mechanisms of these effects are not well understood. Since the majority of the published literature is concerned with cirrhotic liver disease, this review also focuses mainly on this area. Four different theories have been proposed to account for the effects of chronic liver disease with cirrhosis on hepatic drug elimination: the sick cell theory; the intact hepatocyte theory; the impaired drug uptake theory; and the oxygen limitation theory. While some data in support of each of the first 2 theories have been published recently, a large amount of clinical data would appear to refute both of these theories. These clinical data are substantially consistent with the latter 2 theories, which regard the decreased permeability of the capillarised sinusoid as the critical feature in cirrhosis. Further work is required to determine the applicability of each of these theories. In cirrhosis, drug glucuronidation is spared relative to oxidative drug metabolism; however, in advanced cirrhosis this pathway may also be impaired substantially. There is evidence that in cirrhosis other conjugation pathways may also be impaired to variable degrees. Growing evidence suggests that biliary drug excretion is impaired in cirrhosis. Recent studies with several racemic drugs indicate that the disease can have different effects on the hepatic elimination of individual enantiomers, which may lead to a change in the concentration-response relationships of racemic drugs in cirrhosis. A major finding which has emerged in recent years is that, even with moderate degrees of hepatic impairment, there is a decrease in clearance of drugs or active metabolites normally cleared by the kidney. The effect on renal clearance of unbound drug may be masked if there is a concomitant decrease in plasma protein binding of the drug. Neither serum creatinine levels nor creatinine clearance are useful markers of the renal dysfunction associated with cirrhosis. Both may greatly overestimate renal function in patients with cirrhosis due to increased fractional renal tubular secretion of creatinine. Altered receptor sensitivity has been observed with some drugs in cirrhosis, while for other drugs there is no change in pharmacodynamics. Precise determination of drug dosage in cirrhosis requires information on changes in pharmacodynamics and plasma protein binding in addition to changes in drug elimination. Pharmacokinetic investigations in a variety of chronic liver diseases without cirrhosis (e.g. carcinoma, schistosomiasis and viral hepatitis) suggest that in the absence of cirrhosis, impairment of drug elimination is not sufficient to warrant reduction of drug dosage. However, if cirrhosis is present, 'safe' drug use requires an awareness of the possibility of multiple interactions between changes in hepatic and renal disposition and pharmacodynamics. In chronic liver disease with cirrhosis, dosage reduction is the general rule regardless of the route of elimination of drug or metabolite.

Anti-infective agents and hepatic disease

Numerous factors such as changes in plasma protein binding, tissue binding, hepatic blood flow, hepatic metabolism, and distribution may occur in hepatic disease. The impact of these physiologic changes on pharmacokinetic and pharmacodynamic parameters of anti-infective agents is likely to be clinically significant. Unfortunately, these issues have not been thoroughly investigated. Even within the same type of liver disease, there is considerable interpatient variability in pharmacokinetic variables, rendering it difficult to predict drug disposition accurately. Pharmacokinetics of selected anti-infective agents are altered in hepatic disease, necessitating careful monitoring and dosage titration to avoid enhanced drug concentrations and risk of toxicity.

Fleroxacin. A review of its pharmacology and therapeutic efficacy in various infections

The fluoroquinolone antibacterial agent fleroxacin has a broad spectrum of in vitro activity which encompasses most Gram-negative species (particularly Enterobacteriaceae) and a number of Gram-positive organisms, including methicillin-sensitive staphylococci. It is available as oral and intravenous formulations. In clinical trials, fleroxacin has been evaluated in the treatment of uncomplicated urinary tract infections (single or multiple once-daily oral doses of 200 or 400mg), gonorrhoea and chancroid (single oral doses of 200 or 400mg), complicated urinary tract, nonpneumococcal lower respiratory tract and skin and soft tissue infections and typhoid fever (multiple once-daily oral or intravenous regimens, usually 400 mg/day), bacterial enteritis, and traveller's diarrhoea (single or multiple once-daily oral doses of 400mg). Bacteriological cure rates were generally around 90% or higher in complicated and uncomplicated urinary tract infections, uncomplicated gonorrhoea (approximately 100%), pyelonephritis, bacterial enteritis and typhoid fever, and exceeded 80% in lower respiratory tract, and skin and soft tissue infections and chancroid. These cure rates were similar to, or better than, those achieved with standard comparator antibacterial agents such as penicillins, cephalosporins, cotrimoxazole, or other quinolones. Fleroxacin 400mg once daily also achieved bacteriological cure in approximately 80% of patients with bone and joint infections in preliminary studies. In Japanese studies using a lower dosage of 200 or 300 mg/day, fleroxacin was reported to be bacteriologically effective in a range of infections, including urinary tract and upper and lower respiratory tract infections. Fleroxacin has a relatively long elimination half-life, which allows once-daily administration, and it appears to have less propensity for interactions with other medications in comparison to many other fluoroquinolones. Its tolerability profile is typical of this class of compound, with adverse events mostly relating to the gastrointestinal tract, CNS, and skin and appendages (including phototoxicity). Recent pooled tolerability data from worldwide clinical trials indicate that adverse events are reported by approximately 27% of patients receiving 200 mg/day orally or 400 mg/day orally or intravenously, and 17% of those receiving a single oral dose of 400mg. These exceed incidences reported for established fluoroquinolones, possibly indicating recent trends towards increased rates of reported adverse effects with these agents. However, in direct comparative studies with twice-daily fluoroquinolones, fleroxacin 400mg once daily produced a similar incidence of adverse effects to ofloxacin 800 mg/day and a slightly higher incidence than ciprofloxacin 1000 mg/day, while fleroxacin 200mg once daily produced a similar incidence to norfloxacin 800 mg/day.(ABSTRACT TRUNCATED AT 400 WORDS)

Single-dose pharmacokinetics of oral fleroxacin in bacteremic patients

Fleroxacin is a new broad-spectrum quinolone which can be given by the oral route. The present study was designed to assess the influence of bacteremia on the pharmacokinetics of a single oral dose of fleroxacin. Thirteen patients with proven bacteremia (one or more pairs of positive blood cultures, no hypotension) were given a single 400-mg fleroxacin dose orally on two occasions while also receiving standard antibiotic therapy. The first dose was administered 12 to 36 h after the last positive blood culture was drawn (day 1), and a second dose was administered 7 days later (day 7 +/- 2) to compare the pharmacokinetics between the acute and the convalescent phases of the disease. Following each administration of fleroxacin, serial plasma samples were collected for up to 72 h and were analyzed for unchanged drug by a reversed phase high-pressure liquid chromatography technique. There were no significant changes in the following pharmacokinetic parameters (mean standard deviation) the maximum concentration of drug in serum (6.4 +/- 1.5 versus 6.7 +/- 1.9 mg/liter), the minimum concentration of drug in serum, defined as the concentration of drug in serum at 24 h postdose (3.0 +/- 1.7 versus 2.5 +/- 1.2 mg/liter), the time to the maximum concentration of drug in serum (2.3 +/- 1.4 versus 2.0 +/- 1.2 h), and the elimination half-life (19.7 +/- 8.0 versus 17.9 +/- 6.9 h). Fleroxacin clearances were compared for each individual patient. A positive correlation (R2 = 0.787) was found between the values measured on day 1 and day 7. Oral clearance of fleroxacin (CL = CL/F, where F is bioavailability was slightly, but not significantly, reduced during the bacteremic phase (oral clearance, 43.8+/- 23.5 versus 48.5 +/- 17.5 ml/min.). When compared with previous results obtained in healthy young subjects, longer times to the maximum concentration of drug in serum and elimination half-lives and higher areas under the curve were observed. This could be due to the bacteremic state, the old age of the patients (mean, 66 years), and the low renal clearance (mean calculated creatinine clearance, 71.1 ml/min). A single oral dose of 400 mg of fleroxacin provides sufficient levels in serum to cover susceptible microorganisms for at least 24 h in bacteremic patients. Renal function appeared to be the key element that had to be taken into consideration to adapt fleroxacin dosage profiles in our patient population. Bacteremia itself appeared to amplify that phenomenon, but to a much lesser extent than renal function did.

Clinical pharmacokinetics of newer antibacterial agents in liver disease

Liver disease may produce significant, albeit highly variable, effects on the pharmacokinetic behaviour of antibiotics in serum. Drug disposition may be altered through several pathophysiological mechanisms including reduced hepatobiliary clearance, and modifications in the volume of distribution induced by albumin synthesis deficiency or portal hypertension-related ascites. Antibacterial agents are not affected by potential alteration in hepatic first-pass effects. Only liver cirrhosis-induced effects on serum pharmacokinetics of antibiotics have been extensively studied, unlike those possibly produced by other forms of liver disease. In liver cirrhosis, pharmacokinetic alterations of nearly all beta-lactam or quinolone agents appear not to be marked enough to require dosage adjustment, provided that renal function stays normal. Adaptation in therapeutic schedule, however, is warranted for those drugs that are substantially cleared by the hepatobiliary system, namely mezlocillin, clindamycin, erythromycin, pefloxacin, enoxacin, antituberculous agents or nitroimidazole derivatives. Special caution should also be exercised when using aminoglycosides or vancomycin because of the wide interpatient variability of their pharmacokinetic disposition and their toxic potential. When renal function is impaired and there is an increased volume of distribution due to ascites, as frequently observed in severe liver insufficiency, the elimination half-life of most antibiotics is markedly prolonged, resulting in potential side effects due to drug accumulation. Accordingly, dosage adjustment applies to all drugs. In this regard, it should be remembered that delineating the dosage guidelines for a given antibiotic on the basis of reported pharmacokinetic parameters in patients with liver cirrhosis is awkward and probably of limited value. This pattern is ascribed to large interpatient variability in the active hepatic cell mass, the degree of portal hypertension and the alteration of serum binding capacity. Furthermore, there is no way of predicting accurately the extent of liver insufficiency in an individual patient. Dosage reduction is thus done empirically in most cases. Whenever possible, direct measurements of serum antibiotic concentrations should be the reasonable approach to manage antibiotic therapy in this kind of clinical condition.