Induction of cytochrome P-450 in rat liver by the antibiotic troleandomycin: partial purificaton and properties of cytochrome P-450-troleandomycin metabolite complexes.
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Inactivation of cytochrome P-450 by a troleandomycin metabolite. Protective role of glutathione.
Troleandomycin, a macrolide antibiotic, has been shown to be demethylated and oxidized into a metabolite which forms an inactive complex with the iron(II) of cytochrome P-450. The role of glutathione in the metabolism of troleandomycin was investigated. Administration of troleandomycin (1 mmol X kg-1 p.o.) decreased the concentration of glutathione in the liver. The depletion of glutathione was increased in rats pretreated with phenobarbital and decreased in rats pretreated with CoCl2. In vitro, an inverse relationship was found between the concentration of glutathione in the incubation mixture and the appearance of the cytochrome P-450-troleandomycin metabolite complex. Glutathione, however, did not inhibit the demethylation of troleandomycin and did not destroy the cytochrome P-450-troleandomycin metabolite complex. The in vitro protective effect of glutathione was reproduced by cysteine but not by glycine. In vivo, decreasing the concentration of glutathione in the liver by food deprivation or by the administration of diethylmaleate increased the formation of the cytochrome P-450-troleandomycin metabolite complex. These results indicate that glutathione is depleted by a troleandomycin metabolite in vivo, whereas glutathione protects against the formation of the inactive cytochrome P-450-troleandomycin metabolite complex in vitro and in vivo.
Animals↗
Inhibition of rat liver estrogen 2/4-hydroxylase activity by troleandomycin: comparison with erythromycin and roxithromycin.
Administration of troleandomycin (0.5 mmol.kg-1 p.o. daily for 5 days) decreased by 61% and 36%, respectively, the estradiol and ethinylestradiol 2/4-hydroxylase activities of hepatic microsomes from male Sprague-Dawley rats killed 2 hr after the last dose. This decrease did not appear to be due to the in vivo formation of the inactive cytochrome P-450 p Fe(II)-metabolite complex, since disruption of this complex with potassium ferricyanide did not increase estrogen hydroxylase activities. Troleandomycin administration, however, essentially suppressed cytochrome P-450 UT-A (one of the P-450 forms involved in the hydroxylation of estrogens) and resulted in the appearance of cytochrome P-450 forms whose estradiol hydroxylase activity was inhibitable by troleandomycin in vitro. Similarly, troleandomycin (2 mM) inhibited by 60% estradiol and ethinylestradiol 2/4-hydroxylase activities in microsomes from dexamethasone-treated rats, although it had no inhibitory effect in microsomes from control rats. In contrast, erythromycin and roxithromycin (2 mM) exerted no inhibitory effect, even in microsomes from dexamethasone-treated rats. In vivo, these macrolides (0.5 mmol.kg-1 p.o. daily for 5 days) decreased moderately cytochrome P-450 UT-A levels and estradiol 2/4-hydroxylase activity, and did not modify ethinylestradiol 2/4-hydroxylase activity. We conclude that the administration of troleandomycin, but not that of erythromycin or roxithromycin, decreases ethinylestradiol 2/4-hydroxylase activity in male rat liver microsomes, as a possible consequence of decreased cytochrome P-450 UT-A levels and of the induction of glucocorticoid-responsive P-450 forms whose ethinylestradiol hydroxylase activity is inhibitable by troleandomycin.
Animals↗
Formation of an inactive cytochrome P-450 Fe(II)-metabolite complex after administration of troleandomycin in humans.
In rats, it has been shown that troleandomycin induces its own transformation into a metabolite forming an inactive complex with reduced cytochrome P-450. To determine whether similar effects occur in humans, we studied hepatic microsomes from 6 untreated patients and 6 patients treated with troleandomycin, 2 g per os daily for 7 days. In the treated patients, NADPH-cytochrome c reductase activity was increased by 48%; total cytochrome P-450 concentration was also increased, but 33% of total cytochrome P-450 was complexed by a troleandomycin metabolite. The cytochrome P-450 Fe(II)-metabolite complex exhibited properties identical to those of the inactive complex formed in rats: it exhibited a Soret peak at 456 nm, was unable to bind CO, and was destroyed by addition of 50 microM potassium ferricyanide. We also measured the clearance of antipyrine in 6 other subjects. This clearance was decreased by 45% when measured again on te seventh day of the troleandomycin treatment. We conclude that repeated administration of troleandomycin induces microsomal enzymes, produces an inactive cytochrome P-450 Fe(II)-metabolite complex, and decreases the clearance of antipyrine in humans.
Adult↗
Inhibition of theophylline clearance by troleandomycin.
The effect of troleandomycin, a macrolide antibiotic, on theophylline elimination was examined in eight patients with chronic asthma. Clearance from serum was reduced by 50 +/- 6% (mean +/- SD) during administration of 250 mg troleandomycin four times daily. Reduction of clearance persisted to a lesser degree in one of these patients examined while receiving 250 mg troleandomycin daily. An increase in serum theophylline concentration can thus result from initiating troleandomycin in asthmatic patients receiving continuous treatment with theophylline. This may be at least a partial explanation for the apparent benefit of troleandomycin in chronic asthma and also suggests that possibility of inducing theophylline toxicity, including seizures, as was observed in one of the patients in this study.
Drug Interactions↗
[A new cause of torsades de pointes: combination of terfenadine and troleandomycin].
The authors report a case of wave-burst arrhythmia which occurred during combined treatment with terfenadine and troleandomycin. After the treatment had been stopped and the QT interval returned to normal, terfenadine treatment was reintroduced with no major change in repolarization. However, as soon as troleandomycin was associated, there was a significant and progressive prolongation of QT. Normal repolarization was restored again with troleandomycin alone. These findings suggest drug interaction between terfenadine and troleandomycin. Although it is not possible to carry out serum assays of terfenadine, one possible physiopathological hypothesis would be an overdose of terfenadine. Terfenadine undergoes hepatic oxidative metabolism involving the cytochrome P450 pathway and troleandomycin inhibits cytochrome P450. In the literature, a case has already been described of wave-burst arrhythmia related to terfenadine overdose when associated with a cytochrome P450 inhibitor.
Aged↗
Troleandomycin-triazolam interaction in healthy volunteers: pharmacokinetic and psychometric evaluation.
Seven healthy volunteers received a single oral dose of triazolam 0.25 mg after 7 days on troleandomycin 2 g/day p.o. or placebo in a double-blind cross-over study. Plasma triazolam and psychometric and memory tests (including Critical Flicker Fusion threshold, Choice Reaction Time, Digit Symbol Substitution and Self-Rating Scales) were assessed at regular intervals after the final treatment. Troleandomycin was found to prolong the psychomotor impairment and amnesia produced by triazolam. There was a significant enhancement of the AUC, the peak concentration and the delay to tmax of triazolam after 7 days treatment with troleandomycin compared to placebo. Thus, there is a pharmacokinetic interaction, and the combination of triazolam and troleandomycin should be avoided or the dose of triazolam should be adjusted. The most likely mechanism is a diminished hepatic first-pass effect, and a decrease in the apparent oral clearance of triazolam.
Adult↗
Maternal environment defines blood pressure and its response to troleandomycin in spontaneously hypertensive rats.
Relationship between family-3A cytochrome P-450-dependent (troleandomycin inhibitable) and maternal environmental-dependent systolic blood pressure (SBP) was investigated in spontaneously hypertensive rats (SHR). Adult SHR nursed by foster or natural SHR mothers had indistinguishable SBP. Troleandomycin reduced 50% of Wistar-Kyoto (WKY)-SHR strain difference in SBP. SHR having WKY foster mothers had SBP similar to troleandomycin-reduced SHR levels, which was unaffected by troleandomycin. The two components of SBP elevation appear identical. Because observations of others demonstrated that WKY fostered to SHR show no SBP increase, the maternally dependent/troleandomycin-sensitive component of SBP elevation may reflect epistatic interaction between genes determining maternal differences and offspring sensitivity, respectively.
Animals↗
Comparative study of erythromycin, troleandomycin and tylosin on the rabbit intestine.
The macrolide antimicrobial agents, erythromycin, troleandomycin and tylosin were tested for their effect on isolated whole segments of the rabbit duodenum, jejunum, ileum and ascending colon, as well as on strips of the circular and longitudinal smooth muscle of the ascending colon. The 14-membered macrolides erythromycin and troleandomycin were found to possess a concentration-dependent contractile effect on the intestinal smooth muscle. The order of potency was: erythromycin > troleandomycin. The 16-membered macrolide tylosin was found to have a much weaker potency than erythromycin and troleandomycin. In addition, the circular smooth muscle of the ascending colon was found to be more sensitive to the compounds tested than the longitudinal smooth muscle.
Animals↗
Effect of low-dose troleandomycin on glucocorticoid pharmacokinetics and airway hyperresponsiveness in severely asthmatic children.
Fifteen hospitalized asthmatic children (8 to 18 years old) completed a 2-week randomized, parallel, double-blind placebo-controlled comparison of combination methylprednisolone and placebo troleandomycin, prednisone and troleandomycin (P-TAO) or methylprednisolone-TAO (MPn-TAO). Troleandomycin (250 mg once daily or every other day) and glucocorticoid doses were reduced by a standard protocol. Symptom scores, blood chemistries, pulmonary function tests, airway response to methacholine, and glucocorticoid pharmacokinetics were compared. In each group, a steroid dose reduction of 50% was achieved without a deterioration in symptom scores. Methacholine response was unchanged in all five on methylprednisolone alone, but decreased 3-fold to 30-fold in two of five on combination P-TAO, and four of five on combination MPn-TAO. Troleandomycin decreased MPn clearance by an average of 62% but did not alter prednisolone clearance. Low-dose TAO combined with MPn has a significant effect on methylprednisolone clearance in children, an effect equivalent to that reported with higher dose TAO (1000 mg/d) therapy. In addition, this preliminary study suggests that TAO may decrease bronchial hyperresponsiveness to methacholine in severely asthmatic children.
Adolescent↗
Prolonged cholestasis after troleandomycin-induced acute hepatitis.
We report the case of a patient in whom troleandomycin-induced hepatitis was followed by prolonged anicteric cholestasis. Jaundice occurred after administration of troleandomycin for 7 days and was associated with hypereosinophilia. Jaundice disappeared within 3 months but was followed by prolonged anicteric cholestasis marked by pruritus and high levels of alkaline phosphatase and gammaglutamyltransferase activities. Finally, pruritus disappeared within 19 months, and liver tests returned to normal 27 months after the onset of hepatitis. This observation demonstrates that prolonged cholestasis can follow troleandomycin-induced acute hepatitis.
Acute Disease↗
Use of troleandomycin as a steroid-sparing agent in both asthma and chronic obstructive pulmonary disease.
Troleandomycin has been reported to be useful for reducing the steroid requirement of patients with asthma. The purpose of this study was to evaluate the usefulness of troleandomycin in treating patients with steroid-dependent asthma as well as in patients with steroid-dependent chronic obstructive pulmonary disease (COPD). Twelve patients with obstructive airway disease were studied; 6 patients had a diagnosis of asthma, and 6 patients had COPD. All had failed previous attempts to reduce their dosage of steroids. Among the patients with asthma, it was possible to taper methylprednisolone dosage from 29.3 +/- 21.8 mg to 11.1 +/- 7.4 11.1 mg (P less than .05). In the group with COPD there was also a significant decrease in steroid dosage--from 22.6 +/- 12.2 to 6.0 +/- 4.5 mg. These changes were not associated with a decline in spirometric values; nor was improvement secondary to improved theophylline levels, as demonstrated by a significant decrease in serum theophylline levels from 12.4 +/- 3.6 mg/dL baseline to 8.5 +/- 2.8 mg/dL (P less than .001) after maximal steroid tapering. We conclude that troleandomycin is effective in reducing the steroid dosage in patients with COPD or asthma.
Adrenal Cortex Hormones↗
Mechanism of uptake of dihydroergotamine by isolated rat hepatocytes: effect of troleandomycin.
The mechanism of uptake of dihydroergotamine (DHE) was studied in isolated rat hepatocytes and the effect of troleandomycin on DHE uptake was examined. The uptake was linear for 75 sec and reached an equilibrium at 5 min with an intracellular/extracellular concentration ratio of approximately 65. The initial velocity of uptake was linearly related to the concentration of DHE in the extracellular medium with a diffusion constant of 127 pmol X min-1 X mg of protein-1 X microM-1. Metabolic inhibitors (KCN, carbonylcyanide-M-chlorophenylhydrazone and antimycin A) had no effect on DHE uptake. Replacement of sodium by choline chloride in the extracellular medium decreased slightly but significantly (P less than .02) the uptake of DHE. The addition of troleandomycin (300 microM) in the incubation medium decreased the initial velocity of uptake of DHE (control, velocity of uptake = 88 pmol X min-1 X mg of protein-1 X microM-1; troleandomycin, velocity of uptake = 55 pmol X min-1 X mg of protein-1 X microM-1; P less than .05). These results suggest that DHE enters into the hepatocytes by passive diffusion. The high intracellular/extracellular concentration ratio suggests that intracellular binding occurs and results in an accumulation of DHE in the cells.
Animals↗
Effects of troleandomycin administration on cholesterol 7 alpha-hydroxylase activity and bile secretion in rats.
Repeated administration of troleandomycin increased bile flow but decreased the biliary secretion of bile acids in rats. The increased bile flow was associated with a parallel increase in the biliary clearance of [14C]erythritol. Analysis of the relationship between bile flow and bile acid secretion indicated that, for any given rate of bile acid secretin, bile flow was higher in troleandomycin-treated rats than in control rats. The increased bile flow was associated with an increased activity of Na+,K+-adenosine triphosphatase in liver plasma membranes. The decreased bile acid secretion into bile was associated with a similar decrease in the bile acid pool size, a decreased bile acid synthesis rate and a decreased activity of microsomal cholesterol 7 alpha-hydroxylase. The concentration of bile acids in serum, the hepatic extraction ratio of [3H]taurocholate and its biliary transport maximum were not modified. It is concluded that repeated administration of troleandomycin increases the canalicular bile acid-independent flow but decreases the activity of cholesterol 7 alpha-hydroxylase, the synthesis, the pool size and the biliary secretion rate of bile acid in rats.
Animals↗
Analysis of cortisol, methylprednisolone, and methylprednisolone hemisuccinate. Absence of effects of troleandomycin on ester hydrolysis.
A sensitive, selective, and reproducible high-performance liquid chromatographic assay for the simultaneous measurement of cortisol and methylprednisolone using dexamethasone as the internal standard is presented. Samples are extracted with methylene chloride, washed with sodium hydroxide and then water, and chromatographed on a microparticle silica gel column with ultraviolet detection at 254 nm. Sensitivity is greater than 10 ng/ml and the intra-day coefficient of variation is less than 5% for both steroids. The use of porcine liver esterase allows the quantitation of the hemisuccinate ester of methylprednisolone. This assay has been applied in pharmacokinetic studies including investigations of troleandomycin--methylprednisolone interactions. A typical plasma concentration--time profile for methylprednisolone and its ester prodrug is presented for one subject before and after receiving troleandomycin therapy. Although methylprednisolone elimination is reduced in the presence of troleandomycin therapy, there is no effect on the pharmacokinetics of methylprednisolone sodium succinate.
Adult↗
Effects of troleandomycin and josamycin on thyroid hormone and steroid serum levels, liver function tests and microsomal monooxygenases in healthy volunteers: a double blind placebo-controlled study.
Serum TSH levels are moderately but significantly (P ANOVA: 0.05) decreased by troleandomycin (T; 1 g bid over a 10-day period) compared with josamycin (J) (same doses) and placebo (P) in healthy volunteers. T also significantly increases serum estradiol concentration (P ANOVA: 0.03). This effect may be related to a T-induced inhibition of some P450 monooxygenase isoenzymes and more specifically P 450 NF, determined in our study by a decrease in urinary excretion of 6-beta-hydroxy-cortisol. Troleandomycin and josamycin both show poor upper GI tolerance. Liver enzymes (SGOT, SGPT, alkaline phosphatase and gGT) are significantly altered by T compared with J and P (P ANOVA: 0.007, 0.001, 0.09 and 0.04 respectively). After J, liver function tests are very close to control values (placebo). Liver enzymes are significantly more altered by T than by J (P 0.004, 0.001 and 0.06 for SGOT, SGPT and gGT respectively). Using 6 volunteers in a latin-square designed study, some established effects of oral macrolides were confirmed (poor upper GI tolerance; liver toxicity of T). Some other effects of T were also elicited, which were either unknown (decrease in serum TSH) or expected but which had not previously been assessed in man (increase in serum estradiol; decreased urinary excretion of 6-beta-hydroxy-cortisol).
Adult↗
Methylprednisolone and troleandomycin in treatment of steroid-dependent asthmatic children.
Oral methylprednisolone combined with troleandomycin has been reported to be successful in treating poorly controlled, severe asthma in adults. We found this drug combination to be effective in treating 11 steroid-dependent children with poorly controlled asthma who were aged 7 to 13 years, for 12 to 28 months. Improvement of clinical and pulmonary functions was achieved within seven days, with the forced expiratory volume in 1 s increasing by 38% and the maximal midexpiratory flow rate increasing by 55% over the baseline value. By one year, the former improved to 98% of predicted value and the latter, to 79% of predicted value. Compared with the prior 12 months, patients at this time required fewer emergency visits, missed fewer days of school, and had fewer hospitalizations. Side effects included transient-increased cushingoid features, abdominal pain, and liver enzyme level elevation. Patients showed less evidence of adrenal suppression.
Administration, Oral↗
Effect of glutathione depletion on the in vivo inhibition of drug metabolism by agents forming an inactive cytochrome P-450 Fe(II):metabolite complex. Studies with amiodarone and troleandomycin.
The relative contribution of competitive inhibition versus formation of a P-450:metabolite complex to the in vivo inhibition of drug metabolism for several agents is unclear. The present investigation examined the contribution of these two mechanisms to the in vivo inhibition of drug metabolism by amiodarone through manipulation of glutathione turnover. In vivo P-450-dependent metabolism in rats was assessed by determining antipyrine clearance. Pretreatment with amiodarone (50 mg/kg, iv) decreased antipyrine clearance with or without prior glutathione depletion. Depletion of glutathione by buthionine sulfoximine (1.6 g/kg, ip) did not enhance the magnitude of inhibition of antipyrine clearance by amiodarone. Moreover, administration of a normally subinhibitory dose of amiodarone after buthionine sulfoximine pretreatment did not influence antipyrine clearance. Similarly, depletion of glutathione via buthionine sulfoximine or diethylmaleate (1 mL/kg, po) did not influence the magnitude of inhibition caused by a single po dose of troleandomycin (500 or 350 mg/kg, respectively). These data indicate that glutathione content may not be a critical determinant for the in vivo inhibition of drug metabolism by agents which form a P-450:metabolite complex.
Amiodarone↗