Cardiotoxicity and cytotoxicity of the anthracycline analog 4'-deoxy-4'-iodo-doxorubicin

The cardiotoxicity and cytotoxicity of the novel doxorubicin (DXR) derivative 4'-deoxy-4'-iodo-DXR were evaluated and compared to DXR. A single dose of DXR 10 mg/kg i.v. in anesthetized rats induced a significant widening of S alpha T segment of the electrocardiogram, an increase in both mean arterial blood pressure and heart rate and a fall in systemic arterial dP/dtmax, while 4'-deoxy-4'-iodo-DXR 4 mg/kg i.v. induced a significant widening of S alpha T segment and an increase in mean arterial blood pressure. A chronic cardiomyopathy was induced over a 6-week period by three injections of DXR 3 mg/kg per week i.v. and was characterized by a progressive enlargement of S alpha T segment, a flattening of T wave, the occurrence of arrhythmias and histological alterations of myocardium. The contractile responses to adrenaline of isolated hearts from DXR-treated animals were significantly reduced compared to controls. 4'-Deoxy-4'-iodo-DXR (1.2 mg/kg per week three times) induced minor ECG alterations and sporadic episodes of arrhythmias. The contractile responses of isolated hearts were not significantly different from those of controls and microscopic examination of hearts revealed only minor changes. Cytotoxicity in vitro was evaluated by the colony formation assay; based on IC50, 4'-deoxy-4'-iodo-DXR was up to six times more cytotoxic than DXR on four human cancer cell lines. These results suggest that 4'-deoxy-4'-iodo-DXR is significantly less cardiotoxic and more cytotoxic than DXR.

Suramin, a novel antitumor compound

Suramin, a polyanionic compound originally synthesized for use as an antiparasitic agent, has recently entered clinical trials for the treatment of a variety of human cancers refractory to conventional modalities of therapy. This is based on suramin's ability to bind and to inactivate growth factor and enzyme systems critical to cellular homeostasis and proliferation. In addition, this compound possesses adrenocorticolytic properties in vivo and exerts significant cytostatic and cytocidal effects against a variety of human tumor cell lines in vitro. Pilot studies using suramin have thus far been conducted in adrenocortical carcinoma, prostate cancer refractory to conventional hormonal manipulation and nodular lymphomas.

Protective effects of fructose-1,6-diphosphate on acute and chronic doxorubicin cardiotoxicity in rats

The effects of fructose-1,6-diphosphate, an intermediate metabolite of glycolysis, on acute and chronic cardiotoxicity of doxorubicin were investigated in rats. In the acute study, urethane-anaesthetized Wistar female rats treated with 10 mg/kg i.v. doxorubicin developed a widening of the S alpha T segment, an impairment of +dP/dtmax, and tachycardia. Pretreatment with 375 and 750 mg/kg i.p. fructose-1,6-diphosphate prevented the S alpha T segment from widening, whereas only 750 mg/kg i.p. significantly attenuated the heart rate increase. Chronic cardiomyopathy was induced over a 6-week period by weekly doses of 3 mg/kg i.v. doxorubicin, being characterized in vivo by the progressive enlargement of the S alpha T segment and the occurrence of histological alterations and in vitro by a marked impairment of the inotropic response elicited by adrenaline in isolated hearts from treated rats. Concurrent treatment with 150 and 300 mg/kg i.p. fructose-1,6-diphosphate thrice a week for 6 weeks did not lessen the chronic heart damage, whereas 600 mg/kg given i.p. significantly reduced the widening of the S alpha T segment and the severity of histological damage in vivo, as well as significantly improving the contractile responses of hearts in vitro. These findings suggest that the administration of fructose-1,6-diphosphate plays a protective role in the acute and chronic cardiotoxicity of doxorubicin in the rat.

Cardiac toxicity and antitumor activity of 4'-deoxy-4'-iodo-doxorubicinol

The acute and chronic cardiotoxicity as well as the cytotoxicity of 4'-deoxy-4'-iodo-doxorubicinol (I-DXRol), the major metabolite of the doxorubicin (DXR) derivative 4'-deoxy-4'-iodo-DXR (I-DXR), were compared with those of I-DXR and DXR. In the acute study, anesthetized rats received i.v. DXR (10 mg/kg), I-DXR (4 mg/kg), or I-DXRol (4 mg/kg) and were monitored for ECG (S alpha T segment and T wave), systolic (SBP) and diastolic (DBP) blood pressure, the first derivative of the systemic arterial pressure (SA dP/dtmax), and heart rate. Treatments induced a significant widening of the S alpha T segment, but I-DXRol was significantly less toxic than I-DXR or DXR. As compared with control values, DXR induced a marked increase in SBP and DBP and a decrease in SA dP/dtmax, whereas I-DXR and I-DXRol induced modest changes in hemodynamic parameters. In the chronic study, 3 mg/kg DXR given to rats by i.v. bolus once a week for 3 weeks resulted in severe chronic cardiotoxicity that lasted 6 weeks and was characterized by S alpha T-segment widening, T-wave flattening, and severe cardiac histological damage. Doses of 1.2 mg/kg I-DXR and 1.2 and 2.4 mg/kg I-DXRol, given i.v. once a week for 3 weeks, and 3.6 mg/kg I-DXRol given as a single dose were associated with a significant T-wave voltage reduction; I-DXR and 2.4 mg/kg I-DXRol induced significant histological alterations of cardiac tissue as compared with control values, whereas modest alterations of heart tissue were observed after injections of 1.2 and 3.6 mg/kg I-DXRol in three doses and in a single dose, respectively. The cytotoxicity of the three anthracyclines against one glioblastoma cell line and two human small-cell lung cancer lines was similar. Results indicate that the acute cardiotoxicity of I-DXRol is lower than that of I-DXR and DXR, whereas the chronic heart damage is similar to that induced by I-DXR and significantly lower compared than that caused by DXR. Moreover, the cytotoxicity of the metabolite appears to be similar to that of I-DXR and DXR. The lack of additional cardiac toxicity due to I-DXRol further supports the lower overall cardiac toxicity of I-DXR, which retains a cytotoxic activity similar to that of the parent drug.

Phase II study of high-dose epirubicin in untreated patients with small-cell lung cancer

Eighteen previously untreated patients with histologically confirmed small-cell lung cancer were treated with high-dose epirubicin (course 1, 100 mg/m2; courses 2-6, 140 mg/m2, day 1), every 3 weeks. Overall response rate was 33% (95% confidence limits, 14-52%), including two complete and four partial responses. The response rates for limited (n = 11) and extensive (n = 7) disease patients were 45% and 14%, respectively. With a median follow-up of 18 months, estimated 2-year survival of all patients was 29% and the median duration of response 18.5 months. The dose-limiting toxicity was myelosuppression, with a median granulocyte nadir of 1,150/mm3; 39% of patients had neutropenic fever. Nausea/vomiting, alopecia, and stomatitis were the most common nonhematological toxicities, usually mild to moderate. Acute cardiac toxicity was unusual and no episodes of congestive heart failure were observed. Cumulative doses of 800 mg/m2 were associated with moderate cardiotoxicity (grade 2), as assessed by endomyocardial biopsy and electron microscopy analysis. These results indicate that epirubicin, at the present doses and schedule, is an active single agent in patients with small-cell lung cancer, with acceptable general and moderate cardiac toxicity.

Suramin in adrenal cancer: modulation of steroid hormone production, cytotoxicity in vitro, and clinical antitumor effect

Suramin, a drug known to have antiparasitic effects, has been previously shown to have adrenocorticolytic activity in primates. We now confirm preferential accumulation of this compound in the normal adrenal gland, evaluate its in vitro effect against two human adrenocortical carcinoma cell lines (SW-13 and NCI-H295), and report the clinical activity of suramin in 17 patients with metastatic adrenocortical carcinoma. Inhibition of colony formation occurred in both adrenal cell lines in vitro at concentrations that are clinically achievable in humans. In addition, suramin concentrations as low as 100 micrograms/mL were able to inhibit glucocorticoid, mineralocorticoid, and androgen production by the NCI-H295 cell line. Of 16 patients with adrenocortical carcinoma now evaluable for tumor response, 2 achieved a partial response, 2 had a minor response, and 5 remained with stable disease for periods ranging from 3-10 months; the remainder progressed. One of 7 patients with excessive steroid hormone production achieved a partial normalization of her steroid levels for the duration of suramin therapy in the setting of radiographic disease stabilization. An additional patient treated off-study for lack of radiographically measurable disease, achieved complete normalization of plasma aldosterone levels. We conclude that suramin preferentially accumulates in adrenal cells, induces cytotoxicity and significant down-regulation of steroid hormone production in vitro, and has some therapeutic efficacy as a single agent in patients with metastatic adrenocortical carcinoma.

The penetration of roxithromycin into human skin

The skin penetration of roxithromycin was studied in 27 surgical patients treated with 300 mg orally followed by three oral doses of 150 mg 12-hourly. Peak plasma and skin concentrations of 7.9 +/- 1.2 mg/l and 31.3 +/- 3.7 mg/kg occurred 2.5 and 4 h after last dosing respectively. The plasma and skin half-lives were 7.7 and 6.0 h, and the mean plasma and skin area under the curve values were 64.3 mg/l.h and 155.3 mg/kg.h. Skin/plasma concentration ratios were 4.9 +/- 0.5, 9.7 +/- 1.2, 7.6 +/- 0.8 and 5.9 +/- 1.1, at 3, 4, 5 and 6 h after last dosing respectively. These results demonstrate that roxithromycin achieves high levels in human skin.

Differential affinities of AF-DX 116, atropine and pirenzepine for muscarinic receptors of guinea pig gastric fundus, atria and urinary bladder: might atropine distinguish among muscarinic receptor subtypes?

The pA2 values and the Schild plots of the antimuscarinic drugs AF-DX 116, atropine and pirenzepine for muscarinic receptors of isolated guinea pig gastric fundus (acid secretion) and atrial and urinary bladder preparations (contractile force) obtained from the same animals were calculated against bethanechol as the agonist. The antimuscarinic drugs concentration-dependently shifted the concentration-response curves to bethanechol to the right without any change in the maximum response. The analysis of data based on Schild plots was consistent with a simple competitive antagonism, since regression slopes did not differ significantly from unity. The pA2 values indicated a significantly higher affinity of AF-DX 116 and atropine for atrial muscarinic receptors with respect to those of the gastric mucosa or urinary bladder. By contrast, in the case of pirenzepine the pA2 values for the three tissues did not differ significantly. These results suggest that each examined tissue apparently contains homogeneous population of acetylcholine muscarinic (M2) receptors. The pA2 values found for AF-DX 116 and atropine suggest, however, that the putative M2 subtype of atrial muscarinic receptor differs from both those of the gastric fundus and those of the urinary bladder.

Roxithromycin penetration into gingiva and alveolar bone of odontoiatric patients

The concentrations of the new macrolide antibiotic roxithromycin in plasma, saliva, gingiva, and alveolar bone were studied in 24 odontoiatric patients treated with a first dose of 300 mg p.o. followed by three maintenance doses of 150 mg p.o., 12-hourly. Samples of blood, saliva, gingiva, and bone were collected at various time points up to 24 h after the last dosing, and the roxithromycin concentration was measured microbiologically, using Bacillus subtilis ATCC 6633 as the reference organism. Pharmacokinetic analysis was performed according to a two-compartment open model with first-order absorption. The plasma, gingiva, and alveolar bone peak concentrations were 6.12 +/- 1.94 mg/l, 6.55 +/- 2.54 mg/kg, and 5.09 +/- 1.60 mg/kg, respectively. Low levels of roxithromycin were detected in saliva (0.67 +/- 0.12 mg/l at the 3rd h). The values of the area under the concentration-time curve for plasma, gingiva, and bone were 59.47 mg/l.h, 51.88 mg/kg.h and 46.80 mg/kg.h, respectively; the half-life values were 7.52 h for plasma and 6.36 and 5.20 h for gingiva and bone, respectively. These results indicate that roxithromycin reaches high levels in periodontal tissues.

Superoxide anion production by doxorubicin analogs in heart sarcosomes and by mitochondrial NADH dehydrogenase

This study investigates the effects of daunorubicin, 4-demethoxy-daunorubicin, 11-deoxydaunorubicin, 5-imino-daunorubicin, doxorubicin, 4'-epidoxorubicin and the new derivative 4'-iodo-4'-deoxydoxorubicin, on superoxide anion production in heart sarcosomes and by mitochondrial NADH dehydrogenase. In cardiac sarcosomes all the anthracyclines tested enhanced NADPH-dependent superoxide formation which followed Michaelis-Menten kinetics and their Vmax were similar to that of doxorubicin except 5-iminodaunorubicin which did not affect superoxide production and 4'-iodo-4'-deoxydoxorubicin which showed significantly lower Vmax and Km. The superoxide formation by NADH dehydrogenase in the presence of anthracyclines appeared to follow saturation kinetics, depending by NADH. 4-Demethoxydaunorubicin and 4'-epidoxorubicin showed Vmax higher than that of doxorubicin although the Km values were similar. By contrast 5-iminodaunorubicin failed to increase superoxide production over control levels and 4'-Iodo-4'-deoxydoxorubicin hardly enhanced superoxide production by NADH dehydrogenase. A marked difference of superoxide formation rate was shown for the molecules tested in our in vitro system. The behaviour displayed in vitro by the imino- and iodo-derivatives well correlate to their moderate cardiotoxicity in vivo. For the other molecules tested, the poor correlation between the in vitro production of superoxides and the in vivo cardiotoxicity degree might depend on the pharmacokinetic steps which may modify the cardiac effects of these anthracyclines.

Depression of the immune responsiveness in mice treated with thioacetamide after antigen exposure

The effects of the weak carcinogen thioacetamide (TAA) on the mouse immune response have been investigated. TAA administration up to 1 day after antigen priming markedly suppressed the antibody response to both T-dependent (sheep erythrocytes) and T-independent (trinitrophenyl-Ficoll) antigens; the compound was ineffective when given 3 or 4 days after immunization. A significant suppression of the in vitro lymphoproliferative response to the B-cell mitogen S. aureus Cowan I was evident from 3 to 48 h after TAA treatment. On the other hand, cell-mediated immune response to oxazolone was suppressed by TAA at each time tested, including that of challenge. The in vitro lymphoproliferative response to concanavalin A was decreased 12 h after TAA administration only, when adenosine deaminase activity within lymphocytes was increased. Furthermore, TAA is endowed with anti-inflammatory activity, as shown by the decreased footpad swelling and by evaluation of the inflammatory cell infiltration upon carrageenan injection. Taken together, these findings suggest selective TAA interaction with multiple targets within the immune system, including B- and T-lymphocytes, while non-specific cytotoxicity can be reasonably ruled out, since hematological determinations and phenotypic analysis of spleen lymphocyte subsets showed no relevant changes.

Evaluation of the JT and corrected JT intervals as a new ECG method for monitoring doxorubicin cardiotoxicity in the dog

A comparison was made of the sensitivity of ECG, ultrastructural heart pathology, and plasma enzymes CK-MB and alpha-HBDH as methods to assess doxorubicin cardiotoxicity in adult beagle dogs given doxorubicin 30 mg/m2 i.v. once a week for three times. A progressive increase in JT and QT intervals, in corrected JT (JTc) and QT (QTc) intervals as well as a reduction in both T wave amplitude and RR duration, were observed in doxorubicin-treated dogs; the electrocardiogram (ECG) abnormalities were associated with doxorubicin-induced ultrastructural changes in cardiac tissue, consisting of dilation of the sarcoplasmic reticulum, multiform, flasklike invaginations of T-tubules containing electrondense material, and interruption of the junctional sarcoplasmic reticulum, which became more severe as the observation period progressed. On the contrary, doxorubicin treatment was associated with transient changes in plasma CK-MB and alpha-HBDH, which were unrelated to the severity of chronic cardiotoxicity. Overall results suggest that the monitoring of the ECG parameters related to the repolarization of the cardiac muscle, and particularly JT and JTc, might be regarded as a noninvasive method for the study of doxorubicin cardiotoxocity in the dog.

[A selective antimuscarinic agent: pirenzepine. Review of its pharmacologic and clinical properties]

The heterogeneity of muscarinic receptors has been well supported by differential characteristics between pirenzepine and atropine both in receptor binding and in whole tissue pharmacology studies. Under these conditions pirenzepine has been classified as a selective receptor antagonist with high affinity for M1 receptors. The antisecretory properties of pirenzepine on gastric acid and pepsin secretion may be attributed to the antagonistic activity of the drug on muscarinic M1 receptors of gastric intramural plexuses, whereas the effect on parietal muscarinic M2 receptors seems of less importance. Additional inhibitory mechanisms on gastric secretion may be represented by pirenzepine-induced increase in somatostatin release from gastrointestinal system. Significant cytoprotective properties of pirenzepine have been observed on a variety of experimentally induced peptic ulcerations. This protective activity may be due to pirenzepine-induced increase in gastric mucosal blood flow as well as to the increase in gastric transmural electric potential difference. In accordance with this pharmacodynamic profile of pirenzepine, numerous clinical studies have revealed its efficacy in the treatment of both duodenal and gastric ulcerations. In addition to this, the clinical usefulness of the drug has been demonstrated in Zollinger-Ellison syndrome, in stress ulceration, in acute gastrointestinal bleeding as well as in gastritis, duodenitis and non-ulcer dyspepsia. In most of the studies pirenzepine has been found to be well tolerated with a low incidence of antimuscarinic effects which may occur at salivary, ocular, cardiac and urinary sites. The clinical use of pirenzepine alone or in association with H2 blockers is recommended in the treatment of peptic ulcer patients, in the case of acute gastrointestinal haemorrhage and in patients non responders to H2 antagonists.

Effects of thymostimulin on chemotherapy-induced toxicity and long-term survival in small cell lung cancer patients

The effects of hymostimulin on chemotherapy-induced toxicity and long-term survival were studied in 26 evaluable patients with small cell lung cancer. Patients were randomly treated with six cycles of two alternating regimens (cyclophosphamide, 4'-epidoxorubicin, and etoposide; cisplatin and etoposide), with (n = 15) or without (n = 11) thymostimulin (1 mg/Kg i.m., days 7-14 of every cycle). Only complete responders received maintenance treatment, consisting of thymostimulin administered 1 mg/Kg i.m., twice weekly, until tumor relapse. Myelosuppression, fever and documented infectious episodes were significantly less severe in thymostimulin-treated patients, allowing the administration of significantly higher drug doses at shorter intervals between chemotherapy cycles; a significant improvement in complete response rate and survival were also observed. Results suggest that the addition of thymostimulin to standard chemotherapeutic regimens might be of benefit, in view of its favourable effects on toxicity and long-term survival.

Fructose-1,6-diphosphate reduces acute ECG changes due to doxorubicin in isolated rat heart

Doxorubicin (DXR) (0.17 x 10(-4) M) induces an acute cardiotoxicity in isolated rat heart; there is a progressive widening of the S alpha T segment, with a decrease in force derivatives and in the coronary flow. Concurrent perfusion with fructose-1,6-diphosphate (FDP) (10(-5)-10(-4) M) dose-dependently reduces the S alpha T enlargement but fails to affect the reduction in force derivatives and coronary flow. The target of cardiac protection by FDP might be the ionic mechanisms underlying the action potential configuration.

Cytofluorescence localization and disposition of doxorubicin and doxorubicinol in rat cardiac tissue

The localization of cardiac cytofluorescence and tissue levels of doxorubicin (DXR) and doxorubicinol (DXR-ol) were studied in rats treated with a single (9 mg/kg: 1-day study) or 3 weekly doses (3 mg/kg: 7-week study) of the compounds. A striking orange-red fluorescence was observed in cardiac cell nuclei from DXR 1-day rats, whilst heart cells from DXR-ol 1-day rats displayed a faint, diffuse fluorescence. Neither cardiac tissue from DXR nor from DXR-ol 7-week animals showed any drug-specific fluorescence. HPLC assay showed that in DXR 1-day rats the drug was concentrated in the heart, which also contained the endogenously produced DXR-ol. Plasma levels of DXR-ol were initially high in DXR-ol 1-day rats but rapidly decreased with time; cardiac levels of DXR-ol remained low. Hearts from DXR 7-week rats contained appreciable amounts of DXR and DXR-ol, while very low levels of DXR-ol were found in DXR-ol 7-week animals. The data correlated well with the ECG alterations recorded during the study, which were more severe in DXR- than in DXR-ol-treated rats. These results indicate that the lower tissue uptake of exogenously administered DXR-ol might explain its lower toxic cardiac potential compared with DXR.

Doxorubicin affects both the number and the morphology of specific atrial granules in dog heart

A morphometric study was performed in dog atria to assess the effects of both single and repeated doses of doxorubicin on specific granules containing the natriuretic factor. Male beagle dogs were divided into 4 groups and treated i.v. as follows: groups A and B were controls and received isotonic saline; group C was given doxorubicin 2.4 mg/kg in a single injection; group D received doxorubicin 1.2 mg/kg once a week for 3 consecutive weeks. Samples of left atrium were taken 8 hours (groups A and C) or 28 days (groups B and D) after the last dose, and examined by the electron microscope. Compared with controls, the atrial tissue of group C dogs showed a significant increase in the number of specific granules; by contrast, the granularity was found to decrease significantly in the atria from group D dogs. These observations indicate a significant biphasic effect of doxorubicin on specific atrial granules of dog heart. The increase in granule density might be due to a block of the secretory process which is dependent on the metabolic energy supply. The reduction in cardiomyocyte granularity may be ascribed to the impairment of nucleic acid and protein synthesis induced by doxorubicin. Such alterations may play a significant role in doxorubicin-induced cardiovascular toxicity.

Plasma pharmacokinetics of cinmetacin following oral administration in healthy volunteers

The pharmacokinetics of a single 600 mg oral dose of 1-cinnamoyl-2-methyl-5-methoxy-3-indolylacetic acid (cinmetacin, Cindomet) was studied in 8 healthy volunteers of both sexes. Plasma levels of the drug were assayed by using an HPLC technique ad hoc devised. Following administration, the Cmax was reached at the 2nd h in 7 out of 8 subjects with an average value of 18.19 micrograms/ml; 12 h after the dose (last sampling time) appreciable plasma levels of cinmetacin were measured, corresponding to 17.2% of the maximum average concentration. The mean values +/- S.E. concerning the elimination half-life, the total volume of distribution, the total plasma clearance and the total area under the curve were 3.80 +/- 0.21 h, 0.28 +/- 0.03 l/kg, 0.051 +/- 0.005 l/kg/h, and 125.64 +/- 15.97 micrograms.h/ml, respectively. The plasma decay of cinmetacin was monophasic and the data were interpreted according to a one-compartment open model. Overall results indicate that cinmetacin is well and rapidly absorbed orally and widely distributed in body fluids.

Exogenous doxorubicinol induces cardiotoxic effects in rats

An investigation was performed in the rat to assess the cardiotoxic effects of exogenous doxorubicinol compared with those induced by an equimolar dose of its parent drug doxorubicin. Rats received synthetic doxorubicinol or doxorubicin 3 mg/kg i.v. weekly for 3 weeks and were observed for a further period of 4 weeks. Survival, body growth, ECG parameters, and heart histopathology were studied. Doxorubicin markedly affected rat body growth, as well as several ECG parameters such as S alpha T, R alpha T, alpha TP and T-wave. Typical cardiac histological alterations were also induced by doxorubicin. In a similar way, doxorubicinol treatment was associated with a significant inhibition of rat body weight increase, and the appearance of ECG alterations as well as both macro- and microscopic signs of cardiac tissue damage. However these effects were delayed in time and their severity was lower compared with doxorubicin. Overall results indicate that doxorubicinol induces a doxorubicin-like toxic syndrome mainly affecting the heart, although to a lower degree of severity than that caused by the parent drug. It is suggested that the lower toxic potential displayed by doxorubicinol might be due at least in part to its greater polarity and a consequently lower cardiac tissue uptake compared with doxorubicin.

Effects of 4'-O-tetrahydropyranyl-doxorubicin on isolated perfused rat heart and cardiac mitochondrial cytochrome C oxidase activity

The acute cardiac effects of the antitumour anthracycline 4'-O-tetrahydropyranyl-doxorubicin (THP) were studied on isolated, perfused, spontaneously beating rat hearts and on cardiac mitochondrial cytochrome c oxidase activity. Perfusion for 1 hour with 2.5 or 5.0 micrograms/ml of THP was associated with a marked widening of the QRS complex and the S alpha T segment, as well as with a reduction of the R- and T-wave amplitude, the heart rate, the isometric systolic tension and the coronary flow. Heart perfusion with equimolar doses of doxorubicin (2.2 or 4.4 micrograms/ml) induced a significant enlargement of the SaT segment and a reduction in the heart rate and the coronary flow. Both anthracyclines inhibited the cytochrome c oxidase activity in a dose-dependent manner; however, THP exerted a significant inhibition at concentrations higher than doxorubicin (20 microM). Results demonstrate that THP induces a higher degree of acute cardiotoxicity on isolated rat hearts compared with doxorubicin. The reduced inhibitory effect of THP on the cytochrome c oxidase activity of isolated heart mitochondria is consistent with the lower degree of chronic cardiotoxicity displayed by THP in animals and humans.

Penetration of clofoctol into human lung

The disposition of clofoctol was determined in plasma and lung tissue from 34 patients undergoing pulmonary resection for lung cancer. Clofoctol 1.5 g was given as a rectal suppository; samples of plasma and pulmonary tissue were collected between 15 and 270 min post-dose. Plasma and lung peak concentrations of the drug were 38.07 +/- 0.73 mg/l and 93.13 +/- 6.68 mg/kg at 30 and 90 min, respectively. Mean values for areas under the concentration-time curve and half-life for plasma and lung were 80.91 mg/l/h, 229.65 mg/h, and 1.18 h and 1.21 h, respectively. Tissue to plasma ratios were 0.85 +/- 0.06, 3.82 +/- 0.21 and 6.19 +/- 0.63 at 30, 90 and 180 min post-dose, respectively. Clofoctol is well absorbed from the rectum and accumulates in lung tissue. This may explain its efficacy in bacterial respiratory infections.

Measurement of the S alpha T segment as the most reliable electrocardiogram parameter for the assessment of adriamycin-induced cardiotoxicity in the rat

A new method is described for the assessment of the early cardiotoxic effects of adriamycin and related drugs on rat electrocardiographic parameters. Evidence is presented that during repeated treatment with adriamycin, no changes occur concerning the PR and RR intervals, QTc, or R- and S-wave voltages, whereas significant changes in the QRS complex, R alpha T and alpha TP intervals, and T-wave voltage are detectable. However, the earliest and most consistent electrocardiogram alteration observed during adriamycin treatment is a progressive, irreversible widening of the S alpha T segment. The S alpha T enlargement becomes significant during the first week of treatment and may be detected in all the tracings at all the times examined. The electrocardiogram changes are accompanied by cardiac histological lesions that gradually increase in severity during the study. These results indicate that the measurement of the S alpha T segment provides a rapid, sensitive, and reliable method for the evaluation of electrocardiogram toxicity induced by adriamycin and related anthracyclines in the rat.