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PubMedDate not supplied

Synthesis, mutagenicity, binding to pBR 322 DNA and antitumour activity of platinum(II) complexes with ethambutol.

Platinum complexes with N,N'-bis(1-hydroxybut-2-yl)ethylenediamine, [PtCl2(ethambutol)] were prepared and the biological activity of three isomers [with (-), (+) and (+/-) ethambutol, respectively] investigated. All species interact with the Bam HI and Ava I recognition sequences showing a binding preference for GC rich sequences of DNA. The complex which showed the greatest interaction with adjacent guanines, [PtCl2[+/-)ethambutol)] was also found to be the most mutagenic of the three. On the other hand, only [PtCl2[+)ethambutol)] had a considerable antitumour activity against both P388 leukaemia and Lewis lung carcinoma, and this was not correlated either with restriction enzyme blocking activity or with mutagenicity.

Animals↗
PubMed1989

[Evaluation of clinical efficacy of isoniazid and ethambutol in the treatment of nontuberculous mycobacteriosis based on in vitro susceptibility testing].

Comparing minimal inhibitory concentrations (MICs) determined in various nontuberculous mycobacteria with those for Mycobacterium tuberculosis strains, which were isolated from patients who were untreated previously by any antituberculosis drugs, clinical efficacy of isoniazid and ethambutol in the treatment of nontuberculous mycobacteriosis was evaluated. The MICs of isoniazid for M. tuberculosis strains were 0.03-0.1 microgram/ml, whereas the MICs for M. xenopi strains were 0.1-0.4 microgram/ml, those for M. szulgai 0.2-0.8, and those for M. kansasii 0.8-1.6 micrograms/ml. The fact that M. xenopi strains are susceptible to isoniazid was reported previously, and in this study, it was shown that M. szulgai and M. kansasii are also considerably susceptible to isoniazid. Isoniazid may be useful in the treatment of infection due to these mycobacteria. The MICs of ethambutol for M. tuberculosis strains ranged from 0.8 to 3.13 micrograms/ml. The percentages of strains of various mycobacteria, which are susceptible to 3.13 micrograms/ml ethambutol, were 100% in M. szulgai, 100% in M. nonchromogenicum, 90% in M. gordonae, 88% in M. marinum, 77% in M. kansasii, 46% in M. malmoense, and 30% in M. scrofulaceum. In contrast, the percentage in M. avium complex strains remained only 19%. It has been suggested that ethambutol is effective in the treatment of diseases caused by M. szulgai, M. marinum and M. kansasii.

Drug Resistance, Microbial↗
PubMed1987

Toxic ocular effects of ethambutol.

Ethambutol hydrochloride has been used in the treatment of tuberculosis for 25 years. Its only important adverse effect, retrobulbar neuritis, is thought to be a minor concern with conventional dosages. The author presents four cases of serious visual impairment due to ethambutol therapy. Three of the patients were receiving a maintenance dosage of 15 mg/kg per day. The fourth patient was inadvertently given 25 mg/kg per day for 4 months. After therapy with the drug was stopped, improvement was slow, with complete recovery in two cases and only minor residual changes in a third. The patient who received the higher dosage of ethambutol suffered permanent, marked impairment. Ethambutol appears to contribute little to modern short-course antituberculous regimens that include more potent agents such as isoniazid and rifampin. In view of this and the potential for serious visual impairment, alternative antituberculous agents should be considered.

Adult↗
PubMed1979

Bilateral optic neuropathy due to combined ethambutol and isoniazid treatment.

The case of a 40-year-old patient who underwent an unsuccessful cadaver kidney transplantation and was treated with ethambutol and isoniazid is reported. A bilateral retrobulbar neuropathy with an unusual central bitemporal hemianopic scotoma was found. Ethambutol was stopped and only small improvement of the visual acuity followed. Isoniazid was discontinued later, followed by a dramatic improvement in the visual acuity. The hazards of optic nerve toxicity due to ethambutol are known. We emphasize the potential danger in the use of ethambutol and isoniazid.

Adult↗
PubMed1983

Ethambutol changes the color coding of carp retinal ganglion cells reversibly.

The influence of ethambutol on retinal function was studied by recording ganglion cell responses in isolated carp retinas superfused with a Ringer solution containing different concentrations of ethambutol (0 mg/liter, 10 mg/liter, 20 mg/liter, 30 mg/liter). The results indicate that ethambutol reversibly affects color opponency, without changing the sensitivity of the underlying receptor processes. The amacrine and bipolar cells are the most likely candidates to be affected by ethambutol.

Action Potentials↗
PubMedDate not supplied

Effect of food on ethambutol absorption.

The effect of food on the absorption of ethambutol hydrochloride tablets was investigated. Following an overnight fast, 11 normal volunteers ingested ethambutol hydrochloride tablets (15 mg/kg dosage) once while fasting and once immediately following a standardized breakfast. The sequence of administration was assigned randomly. Food and fasting trials were at least seven days apart. In both trials, blood samples were drawn at 1, 2, 3, 4, 6, 8, 12, and 24 hours after dosing. Ethambutol concentrations in plasma were determined by a gas-chromatography method. Completeness of absorption was assessed by calculation of the area under the 24-hour plasma concentration curve (AUC) for each subject after each mode of administration using a trapezoidal approximation. Within-subject difference in AUC between food and fasting conditions was evaluated using the Student's t test for paired data. There was no significant difference between the mean AUC-fasting and the mean AUC-food (p greater than 0.05). Food does not appear to influence the extent of ethambutol absorption.

Ethambutol↗
PubMed1993

Ocular ethambutol toxicity: is it reversible?

Delayed onset ocular ethambutol toxicity is usually considered to be reversible following prompt withdrawal of the drug. However, in a series of seven consecutive patients with severe visual deficit due to ethambutol toxicity, only 42.2% (3 of the 7 patients) achieved a visual recovery of better than 20/200 after an average follow-up of 8.3 +/- 2.1 months after stoppage of the drug. On fluorescein angiography, three cases (42.2%) progressed to optic atrophy during the follow-up with permanent visual damage. There were no predisposing or risk factors to contribute toward the poor visual gain. In this background, we recommend discontinuation of ethambutol from the antituberculous regimen. As an additional sidelight, the value of visually evoked potential in the monitoring of patients on ethambutol, especially in cases with early periaxial neuritis, has been emphasised.

Adolescent↗
PubMed1998

Ethambutol-induced pulmonary infiltrates with fever and skin rash: a case report.

A 55-year-old man presented with the suspicion of pulmonary tuberculosis. He was treated with isoniazid, ethambutol, rifampicin and pyrazinamide. However, he developed high fever, skin rash and pulmonary infiltrates following 10 days of treatment. The above-mentioned conditions subsided promptly after stopping ethambutol therapy and reappeared after rechallenge, marking ethambutol as the offender. To present knowledge, this is the second case of an ethambutol-induced hypersensitivity lung reaction reported in English literature.

Antitubercular Agents↗
PubMed1977

Kinetics of oral ethambutol in the normal subject.

Six normal adult volunteers received 15 mg/kg of ethambutol (EMB) by mouth, once as an aqueous solution and again as the commercial tablet preparation. Each dose was separated by at least 7 days. Plasma and urine samples were collected at regular intervals for up to 24 and 72 hr, respectively. Peak plasma concentrations ranged from 3.25 to 5.62 mcg/ml, 2 to 4 hr after tablet dosage. Earlier peak times were found after administering the solution. For plasma concentrations up to 12 hr there was a distinct distribution phase followed by an apparent elimination phase with a mean half-life (t 1/2) (+/- SD) of 4.06 +/- 0.53 and 4.78 +/- 0.41 hr for the tablet and the solution, respectively. Excretion rate plots exhibited similar t 1/2 values for the apparent elimination phase. An even longer t 1/2 of approximately 10 hr was evident from 24-hr plasma samples and urinary excretion measurements up to 72 hr. Unchanged drug excreted in the urine averaged 61.1 +/- 3.8% of the dose for the tablet and 63.4 +/- 2.6% for the solution. Plasma protein binding for ethambutol determined by equilibrium dialysis and ultrafiltration was approximately 20% to 30%. The concentration ratio of ethambutol in erythrocytes to plasma ranged from 1.1 to 1.6.

Administration, Oral↗
PubMed1978

Micro and macro GLC determination of ethambutol in biological fluids.

Previously available GLC methods for ethambutol may only be used to measure quantities of drugs much greater than those found in biological fluids such as plasma and dialysate. A previously published GLC method for plasma samples is extended to measure ethambutol in dialysate. A second GLC method, involving derivatization with bis(trimethylsilyl)trifluoroacetamide and subsequent quantitation using a flame-ionization detector, is described for urine samples. With a dual-column and dual-detector gas--liquid chromatograph, simultaneous micro (plasma and dialysate) and macro (urine) determinations of ethambutol are possible.

Adult↗
PubMed1984

Disposition kinetics of ethambutol in nephrectomized dogs.

The effect of nephrectomy on the disposition of ethambutol was investigated in seven adult mongrel dogs: five were nephrectomized and two served as the control. Each dog was intravenously administered 500 mg ethambutol, followed by blood sample collection for 12 h. Total urine was collected over 24 h from the normal control dogs. Ethambutol contents in plasma and urine were assayed by a GC method. The nephrectomized group and the control group exhibited differences in the following pharmacokinetic parameters: half-life, 5.0 versus 4.1 h (significant at p less than 0.1); total body clearance, 8.4 versus 13.2 mL/min/kg (significant at p less than 0.1); and volume of distribution, 2.7 versus 3.8 L/kg (significant at p less than 0.1). Comparison of pharmacokinetic parameters among rabbits, dogs, and humans revealed distinct interspecies differences with regard to total body clearance, renal clearance, volume of distribution, and fractional renal excretion. One comparable parameter shared by all species is the beta-phase half-life.

Aluminum Hydroxide↗
PubMed1987

Pattern electroretinogram and visual evoked cortical potential in ethambutol optic neuropathy.

Forty-one eyes in 21 cases of ethambutol optic neuropathy were investigated for the pattern visual evoked cortical potential (VECP) and the pattern electroretinogram (ERG). In 21 of the eyes the disappearance VECP responses were not detectable. In the other 20 eyes the peak latency and amplitude of the disappearance VECP were delayed and decreased significantly compared with normal eyes. The recovery of the peak latency of the disappearance VECP in ethambutol optic neuropathy was faster than that of the amplitude. Twelve eyes in six patients were studied by pattern reversal ERG. Though the mean peak latency of the pattern ERG was within normal limits, the mean amplitude was decreased significantly. Our investigations indicated that ethambutol optic neuropathy disturbed not only the optic nerve but also the retina.

Adult↗
PubMedDate not supplied

In vitro testing of clarithromycin in combination with ethambutol and rifampicin against Mycobacterium avium complex.

The activity of clarithromycin in combination with ethambutol and rifampicin was tested at concentrations achievable in serum against 20 strains of Mycobacterium avium complex. The combination of clarithromycin plus rifampicin showed inhibition of 11 of the strains and bactericidal synergism against seven of the strains. When ethambutol was added, a bactericidal effect was observed against 16 strains. On the basis of these in vitro data it seems that clarithromycin in combination with rifampicin and ethambutol may be a promising drug for the effective treatment of infections caused by M. avium complex.

Clarithromycin↗
PubMed1981

Metal binding by pharmaceuticals. Part 1. Copper(II) and zinc(II) interactions following ethambutol administration.

Formation constants for copper(II) and zinc(II) complexes of dextro-2,2'-(ethylenediimino)-di-1-butanol (ethambutol) and its metabolic oxidation product, 2,2'-(ethylenediimino)-dibutyric acid (EDBA) have been measured potentiometrically at 37 degrees C, I = 0.15 mol dm-3 [NaCl]. The constants are used in computer models to assess the extent of the formation of these complexes in vivo. These simulations indicate that whereas ethambutol forms metal complexes only to a limited extent in vivo, EDBA competes effectively under physiological conditions for copper(II) and zinc(II). This study suggests that zinc(II) binding by EDBA may account for a number of side effects of ethambutol treatment.

Chelating Agents↗
PubMed1996

Determination of ethambutol in human plasma and urine by high-performance liquid chromatography with fluorescence detection.

A sensitive and selective HPLC method for the determination of ethambutol in human plasma and urine was developed. Ethambutol was extracted from basified plasma samples (0.2 ml) with diethyl ether, back-extracted into 0.01 M phosphoric acid and derivatized with 4-fluoro-7-nitrobenzo-2-oxa-1, 3-diazole. After 30 min at 80 degrees C and elimination of the reactive excess, the compound was determined by reversed-phase liquid chromatography. urine was analysed for ethambutol after dilution 1:200 with distilled water and derivatization as described for plasma. Quantification in plasma and urine was achieved by fluorescence detection of the eluate. The linearity, precision and accuracy of the method were evaluated. No interference from the constituents of human plasma and urine was observed. The limit of quantification was 10 ng/ml in plasma and 10 micrograms/ml in urine. The suitability of the method for in vivo samples was checked by analysis of plasma and urine samples drawn from healthy volunteers who had received a 1200-mg oral dose of the test compound.

Antitubercular Agents↗
PubMed1975

A comparative study of daily followed by twice or once weekly regimens of ethambutol and rifampicin in retreatment of patients with pulmonary tuberculosis. The results at 1 year. A cooperative tuberculosis chemotherapy study in Poland.

The present report concerns the results at 1 year of a co-operative controlled clinical study carried out in Poland of the retreatment of patients with active, chronic, polyresistant far-advance pulmonary tuberculosis with an oral regimen of daily followed by intermittent ethambutol and rifampicin. A comparison was made of once- and twice-weekly supervised intermittent regimens of rifampicin 1200 mg plus ethambutol 50 mg/kg body weight under out-patient conditions after an initial inpatient phase of rifampicin 600 mg and ethambutol 25 mg/kg daily for 12 weeks. Patients were allocated at random to the regimens. Of 247 patients admitted to the study, 201 (81 per cent) completed 1 year's treatment as prescribed by the protocol, 46 (19 per cent) patients terminated their treatment prematurely before 1 year. After the daily phase of 12 weeks' treatment, 82 per cent were negative on smear and 85 per cent on culture; in the continuation intermittent phase, 98 per cent of patients in the once-weekly (E1R1) regimen were negative on culture at 28 weeks and 98 per cent in the twice-weekly (E2R2) regimen. The corresponding proportions at 52 weeks were 97 per cent and 97 per cent. At 12 months, 96 per cent of 101 ER/E1R1 and 96 per cent of 100 ER/E2R2 patients who completed 1 years' treatment were culture-negative.

Adolescent↗
PubMed1976

A comparative study of daily followed by twice- or once-weekly regimens of ethambutol and rifampicin in the retreatment of patients with pulmonary tuberculosis: second report.

Three hundred and twenty-nine patients with isoniazid-resistant cultures, 66% with radiographically far advanced disease and 86% with cavities, have been treated with rifampicin and ethambutol and followed-up for 2 years after the end of treatment. The drugs were given daily for 12 weeks (600 mg rifampicin and 25 mg/kg ethambutol), thereafter once- or twice-weekly (600 or 1200 mg rifampicin and 50 mg/kg ethambutol) for a total of 12, 18 or 24 months (in the 600 mg group for 12 months only). With both 600 and 1200 mg rifampicin dosage the bacteriological results at the end of a year were similar (5% bacteriologically unfavourable in each group). Prolonging treatment to 18 or 24 months with the 1200 mg rifampicin dose had no effect on the bacteriological results. During the 2 years follow-up period after treatment stopped 6 patients had a bacteriological relapse. Of the 74 with a favourable status after 1 year in the 600 mg rifampicin group 5 (6.7%) relapsed, but only 1 (0.6%) of 168 in the 1200 mg groups treated for 12, 18 or 24 months (the duration of treatment did not appear to be related to relapse). Side-effects were reported more frequently with once-weekly dosage. They were more frequent with 1200 mg rifampicin than with 600 mg and with the former dose more frequent in the groups treated for longer than 1 year. With 12 months treatment with 600 mg rifampicin only 1% of patients had to have the regimen changed; with 1200 mg it was 9% and with this dose for 24 months 20%. With the lower dosage of rifampicin there were fewer failures due to toxicity but more failures due to relapse. Of 82 patients in the 600 mg regimen there were 12% unfavourable results (4 bacteriological failures, 5 relapses and 1 change of treatment for toxicity). Of 78 patients in the 1200 mg regimen there were 13% unfavourable results (3 bacteriological failures, no relapses and 7 changes of treatment for toxicity).

Age Factors↗
PubMed1978

Ethambutol and intra-ocular pressure.

Two groups of Korean patients with tuberculosis, matched in pairs for age and duration of chemotherapy, have been studied. One group had received ethambutol in a mean dosage of 14.4 mg/kg and the other antituberculosis chemotherapy not including ethambutol for at least 3 months. All patients had routine ophthalmological assessments on admission to the study, including examination of the fundi, visual fields and macular thresholds. Intra-ocular pressures were measured and a water-drinking test was then carried out. All the assessments were made by the same ophthalmologist who was at all times kept unaware of the treatment which each patient was receiving or which patients were paired. There was no evidence of ocular toxicity or that ethambutol in the dosages studied has an effect on intra-ocular pressure.

Adult↗