Intrapulmonary pharmacokinetics of ofloxacin in drug-resistant tuberculosis.

OBJECTIVE: To determine the lung epithelial lining fluid (ELF) and serum levels of ofloxacin in drug-resistant tuberculosis patients during treatment. DESIGN: Ten drug-resistant tuberculosis patients treated with ofloxacin containing regimens for at least 2 weeks were enrolled in the study. Subjects ingested ofloxacin 10 mg/kg and other anti-tuberculosis agents after overnight fasting. RESULTS: Serum and bronchoalveolar lavage fluid were collected at 4 hours after treatment and assayed by high performance liquid chromatography. The mean concentrations of ofloxacin in serum and ELF were 5.889 +/- 1.096 and 16.583 +/- 8.697 mg/L, respectively. The mean ratio of ELF-to-serum ofloxacin concentration was 2.825 +/- 1.275. CONCLUSION: Ofloxacin can penetrate well into the intra-alveolar fluid of patients treated for drug-resistant tuberculosis. The lung ELF concentrations were consistently higher than the minimal inhibitory concentrations of Mycobacterium tuberculosis as determined in vitro.

Effect of turpentine-induced inflammation on the disposition kinetics of propranolol, metoprolol, and antipyrine in the rat.

Plasma concentrations after oral administration of the high extraction drug propranolol are increased in patients and animals with inflammation. This could be due to increased serum propranolol binding, but also to decreased first-pass metabolism. We studied the pharmacokinetics of 3 drugs in control rats and in rats with turpentine-induced inflammation: propranolol, which is bound extensively to alpha 1-acid glycoprotein (alpha 1-AGP); metoprolol, another high extraction drug, but which is negligibly bound to alpha 1-AGP; and antipyrine, a low extraction drug, not bound to serum proteins. After IV administration of propranolol in rats with inflammation, systemic clearance, volume of distribution, and free fraction decreased, and the area under the curve (AUC) increased, whereas the half-life did not change. As the systemic clearance of a high extraction drug such as propranolol depends on hepatic blood flow only, a fall in hepatic blood flow or transition to a low extraction situation should be postulated. After oral administration of propranolol, the AUC was increased 20-fold in rats with inflammation; as the decrease in free fraction was only 4-fold, it can be concluded that a considerable decrease in hepatic intrinsic clearance was present. For metoprolol, in contrast to propranolol, after IV administration, no changes in pharmacokinetic parameters as a result of inflammation were observed. After oral administration, the AUC was increased about 4 times in rats with inflammation; as metoprolol is only negligibly bound to serum proteins, the increase in AUC can be attributed to a decrease in hepatic intrinsic clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of inflammation and proadifen on the disposition of antipyrine, lignocaine and propranolol in rat isolated perfused liver.

The effect of inflammation, induced in rats by injection of turpentine oil, on drug disposition has been evaluated in rat isolated perfused livers. The drugs studied were a low extraction drug, antipyrine, and two high extraction drugs, lignocaine and propranolol. Turpentine significantly increased the half-life of antipyrine and of propranolol, but not that of lignocaine. Proadifen (SKF 525A) significantly increased the half-life of all three drugs. Turpentine decreased the clearance of antipyrine significantly by about 50% and that of propranolol non-significantly by about 20%, but did not affect the clearance of lignocaine. Proadifen significantly decreased the clearance of all three drugs, but this was most pronounced for antipyrine. In both turpentine- and proadifen-treated rats a significant increase in volume of distribution of propranolol was observed. The results show that, as with proadifen, turpentine-induced inflammation affects the hepatic clearance of antipyrine in the rat isolated perfused liver. With both high extraction drugs, the effect of inflammation on their clearance was low or absent, in contrast to the effect of proadifen. This suggests that a possible effect of inflammation on intrinsic clearance is not large enough to influence the hepatic clearance of the high extraction drugs.

In-vitro biotransformation of antipyrine, lignocaine and propranolol in the liver of rats with turpentine-induced inflammation.

In rats with inflammation induced by turpentine injection, changes in drug disposition occur in-vivo and in the perfused isolated liver. Therefore the biotransformation of a low extraction drug, antipyrine, and of two high extraction drugs, lignocaine and propranolol, has been evaluated in the 9000g supernatant fraction of the liver of turpentine-treated rats. Aminopyrine N-demethylase activity and cytochrome P450 content were also measured. Turpentine treatment significantly reduced the in-vitro breakdown of the three drugs; aminopyrine N-demethylase activity and cytochrome P450 content were also decreased. Similar results were found in the proadifen-treated rats, except that in those, the cytochrome P450 content was slightly increased. The changes in drug disposition seen after turpentine-induced inflammation, could therefore be due in part to a change in hepatic enzymatic activity.

Pharmacokinetics of levofloxacin in healthy Thai male volunteers.

The pharmacokinetics of levofloxacin, a new fluoroquinolone, were investigated in 12 healthy Thai male volunteers with an average age (SD) of 22.92 (2.50) years. A single oral dose of 300 mg or 500 mg levofloxacin was given to subjects following an 8- hour overnight fast. The drug was given in a controlled, randomized, 2 x 2 crossover design with a 1 week washout period. Venous blood samples were drawn prior to and from 0.25 up to 48 hours after dosing. Plasma levofloxacin concentrations were determined by HPLC assay. The pharmacokinetics of levofloxacin were well described by a linear, 2-compartment open model with first-order absorption with lag time and first-order elimination. Mean +/- SEM of Cmax after 300 mg and 500 mg dose was 4.83 +/- 0.33 and 7.75 +/- 0.71 micrograms/mL, respectively. Tmax ranged from 0.7 to 0.8 hours for both doses. Mean +/- SEM of AUC0-infinity was 35.77 +/- 2.06 micrograms x h/mL for 300 mg dose and 61.57 +/- 2.84 micrograms x h/mL for 500 mg dose. High distribution with VSS/F value of approximately 1.5 L/kg was demonstrated after both doses. Mean +/- SEM of CL/F value was 8.64 +/- 0.41 L/h and 8.31 +/- 0.37 L/h for a 300-mg and a 500-mg dose, respectively. Long t1/2 beta of 7 to 8 hours with the mean residence time of 10.43 +/- 0.43 hours and 10.49 +/- 0.38 hours after 300 mg and 500 mg dose, respectively, was observed. The results suggested that an oral 300 mg dose once daily provides sufficient Cmax to cover most Gram-negative and atypical bacteria (median MIC90 0.032-0.5 microgram/mL) common in mild to moderate respiratory tract infections or complicated urinary tract infections and Gram-positive bacteria (median MIC90 0.5 microgram/mL) common in skin and soft tissue infections. For severe cases or Streptococcus pneumoniae (MIC90 2 micrograms/mL) infection, a 500-mg dose should be recommended.

SKF 525A displaces drugs from serum alpha 1-acid glycoprotein binding sites.

In vivo treatment of rats with beta-diethylaminoethyl-diphenylpropylacetate hydrochloride (SKF 525A), an inhibitor of hepatic monooxygenases, decreases the serum binding of oxprenolol and propranolol, which bind mainly to alpha 1-acid glycoprotein, but not that of phenytoin, which is bound to albumin. The effect was maximal 40 min after treatment and had disappeared after 6 hr, when enzyme inhibition was still present. A displacing effect was also observed when SKF 525A was added in vitro to serum of rats, dogs and humans and to human alpha 1-acid glycoprotein, whereas binding to human serum albumin was not affected. SKF 525A was found to be equipotent with tris(2-butoxyethyl)phosphate, a known displacer of binding of drugs from alpha 1-acid glycoprotein. When studying the pharmacokinetics or the effects of drugs after SKF 525A pretreatment, the possibility that altered protein binding may influence the findings should be considered.

Effect of inflammation on the metabolism of antipyrine, lidocaine and propranolol in isolated rat hepatocytes.

A decrease of the hepatic intrinsic clearance could contribute to the increase of the plasma concentrations of alpha 1-acid glycoprotein-bound drugs such as propranolol in animals and humans with inflammation. Therefore, the influence of inflammation upon the metabolism of propranolol and another high clearance drug, lidocaine, and of the low clearance drug antipyrine, was studied in isolated rat hepatocytes. For comparative purposes, the influence of the enzyme inhibitor SKF 525A (100 mg/kg i.p.) was also evaluated. Turpentine pretreatment of the rats significantly decreased the metabolism of the three drugs by the hepatocytes; the decrease was least pronounced for propranolol. The inhibitory effect of turpentine-induced inflammation was somewhat lower than that of SKF 525A. These results are in agreement with the results found for the same drugs in the 9,000-g supernatant fraction of the rat liver and point to a marked decrease of intrinsic clearance in some types of inflammation.

Alteration of the pharmacokinetics and metabolism of propranolol and antipyrine elicited by indwelling catheters in the rat.

It has been shown that catheter implantation in rats increases concentrations of propranolol and this is usually explained by the increased serum protein binding of propranolol, as a consequence of the higher serum alpha-1-acid glycoprotein concentration. We investigated in this study whether this increase in propranolol concentration after p.o. administration is not also due to a decreased first pass metabolism. We therefore studied in rats the pharmacokinetics and the in vitro metabolism by hepatocytes, of propranolol and antipyrine, 2 and 48 hr after catheter implantation. After p.o. administration of propranolol, the area under the serum concentration time curve 48 hr after catheter implantation was increased 4-fold as compared to 2 hr. As the unbound propranolol fraction was decreased only by a factor of two, it can be concluded that the hepatic intrinsic clearance was decreased, and this was confirmed by a decreased metabolizing activity in the isolated hepatocytes of these animals. After i.v. administration of antipyrine, the systemic clearance was decreased, the volume of distribution was unchanged and the half-life was increased 48 hr after catheter implantation. As antipyrine is a low extraction drug and is not bound to serum proteins, the decreased systemic clearance suggests a lower hepatic intrinsic clearance, and this was again confirmed by a decreased metabolizing activity in the isolated hepatocytes. These results confirm the important effect of the presence of indwelling catheters on the serum concentrations of antipyrine and propranolol, and suggest that this effect is the result of both an increased serum binding and a decreased hepatic metabolism.

Hydroxyurea increases hemoglobin F levels and improves the effectiveness of erythropoiesis in beta-thalassemia/hemoglobin E disease.

Hydroxyurea (HU) is one of several agents that have been shown to enhance hemoglobin (Hb) F levels in patients with sickle cell disease and may be useful as a therapy for beta-globinopathies. However, limited information exists on the effects of HU in patients with thalassemia. Accordingly, we examined the hematologic effects of orally administered HU in 13 patients with beta-thalassemia/Hb E, including four patients who had been splenectomized. These patients were treated with escalating doses (final range, 10 to 20 mg/kg/d) for 5 months and were observed in the outpatient hematology clinic every 2 to 4 weeks. Complete blood counts including reticulocyte counts, amounts of Hb E and Hb F, G gamma:A gamma and alpha:non-alpha globin biosynthetic ratios were evaluated before and during treatment. Almost all patients responded with an average increase of 33% in Hb F levels, from a mean (+/- SD) of 42% +/- 11% to 56% +/- 8% (P < .0001), and a reciprocal decline in the percentage of Hb E from 59% +/- 9% to 49% +/- 8% (P < .001). Reticulocytosis was decreased from a mean (+/- SD) of 18.0% +/- 15.6% to 11.7% +/- 9.1% (P < .05); there was also a slight (10%) but statistically significant increase in hemoglobin levels and an improved balance in alpha:non-alpha globin chains ratios. The side effects were minimal in most patients, although these patients tended to tolerate a lower dose of HU before significant myelosuppression than has been our previous experience in sickle cell disease. One splenectomized patient died of sepsis during the trial. We conclude that increased Hb F production in beta-thalassemia/Hb E patients, with an improvement in the alpha:non-alpha globin ratios and, probably, the effectiveness of erythropoiesis, can be achieved using HU. Longer trials of HU in this population, including at other doses and in combination with other agents, appear warranted.