Increased Brain Serotonin Rather Than Increased Blood Acetaldehyde as a Common Denominator Behind Alleged Disulfiram-Like Reactions.

Several pharmaceutical agents are known to produce ethanol intolerance, which is often depicted as disulfiram-like reaction. As in the case with disulfiram, the underlying mechanism is believed to be the accumulation of acetaldehyde in the blood, due to inhibition of the hepatic aldehyde dehydrogenases, albeit this has not been confirmed in all cases by blood acetaldehyde measurements. Herein, cefamandole, cotrimoxazole, griseofulvin, procarbazine, and propranolol, which are reported to produce a disulfiram-like reaction, as well as disulfiram, were administered to Wistar rats and the hepatic activities of ethanol metabolizing enzymes along with the levels of brain monoamines were determined. Blood acetaldehyde was also evaluated after ethanol administration in rats pretreated with the abovementioned pharmaceutical products. Disulfiram, cefamandole, and procarbazine significantly increased blood acetaldehyde levels after ethanol administration, while on the contrary, cotrimoxazole, griseofulvin, and propranolol had no effect on blood acetaldehyde. Interestingly, all substances used, except disulfiram, increased the levels of brain serotonin. According to our findings, cotrimoxazole, griseofulvin, and propranolol do not produce a typical disulfiram-like reaction, because they do not increase blood acetaldehyde when given together with ethanol. On the other hand, all tested agents share the common property to enhance brain serotonin, whereas a respective effect of ethanol is well established. Hence, the ethanol intolerance produced by these agents, whether blood acetaldehyde concentration is elevated or not, could be the result of a "toxic serotonin syndrome," as in the case of the concomitant use of serotonin-active medications that provoke clinical manifestations similar to those of a disulfiram reaction.

Introduction of Z-GP scaffold into procarbazine reduces spermatoxicity and myelosuppression.

Incorporation of carbobenzoxy-glycylprolyl (Z-GP) to either α or ß position of the hydrazine moiety in procarbazine (Pcb) has been carried on in 5-steps process. The overall yield was 32.7%. The new entity Z-GP-Pcb was confirmed targeting to fibroblast activation protein-α (FAPα). Z-GP-Pcb may be hydrolyzed by either isolated rhFAPα or tumor homogenate. It was shown far less cytotoxicity against NCI-H460 cell line than Pcb. Z-GP-Pcb was displayed the potency to reduce spermatoxcity in H22-bearing mice. The mechanism may be ascribed to the blockade of dehydrogenation by α-glycerolphosphate dehydrogenase. This candidate was further proved equal antitumor activity to Pcb. However, the introduction of Z-GP scaffold decreased myelosuppression. All the evidences support that Z-GP-Pcb is a better antitumor agent than Pcb.

Prolonged survival associated with the use of intraoperative carmustine (Gliadel) in a paediatric patient with recurrent grade III astrocytoma.

A 15-year-old female presented with a middle cranial fossa anaplastic astrocytoma that was completely excised. She received local radiotherapy (54 Gy) and oral temozolomide. Five months after therapy, MRI showed local relapse. She underwent resection of the tumour with implantation of seven carmustine-impregnated wafers (Gliadel). She then received six cycles of procarbazine and lomustine therapy. Three years later, she is well and disease free. This case supports the further investigation of Gliadel in children and young people with relapsed high-grade glioma, particularly in the setting of a second complete resection.

Chemotherapy in low-grade gliomas.

PURPOSE OF REVIEW: This review summarizes the recent studies in adults' diffuse low-grade gliomas (LGGs) chemotherapy, including response assessment and potential predictive biomarkers of chemosensitivity. RECENT FINDINGS: Recent studies have confirmed that chemotherapy is an interesting treatment option in LGGs. About 25-50% of LGGs achieve radiological responses with temozolomide or a procarbazine-CCNU-vincristine (PCV) regimen. Clinical and quality-of-life improvements are commonly observed with more than half of the patients with epilepsy, demonstrating a significant reduction of seizure frequency. Dynamic volumetric studies have provided a better description of LGGs evolution after chemotherapy. They have shown that an ongoing volume decrease can be observed many months after chemotherapy discontinuation, particularly after PCV, raising the question of how and for how long should LGGs be treated. New response criteria have been defined by the Response Assessment in Neuro-Oncology group. In addition to 1p/19q codeletion and MGMT promoter methylation, IDH1 mutation might also be a potential predictive biomarker of chemosensitivity. SUMMARY: It has now been widely accepted that chemotherapy is an interesting treatment option in LGGs. However, several questions remain unanswered regarding its optimal use. Ongoing phase III studies will allow a better delineation of the role of chemotherapy in LGGs and will also help to better determine the potential predictive value of a 1p/19q codeletion, a MGMT promoter methylation and an IDH1 mutation.

ABVD and BEACOPP regimens' effects on fertility in young males with Hodgkin lymphoma.

PURPOSE: Considering the increased cancer patient survivorship, the focus is now on addressing the impacts of treatment on quality of life. In young people, altered reproductive function is a major issue and its effects in young males are largely neglected by novel research. To improve clinician awareness, we systematically reviewed side effects of chemotherapy for Hodgkin lymphoma (HL) in young males. METHODS: The review was prospectively registered (PROSPERO N. CRD42019122868). Three databases (Medline via PUBMED, SCOPUS, and Cochrane Library) were searched for studies featuring males aged 13-51-years who underwent chemotherapy for HL using ABVD (Adriamycin® (doxorubicin), bleomycin, vinblastine, and dacarbazine) or BEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisolone) regimens. These chemotherapy regimens were compared against each other using sperm characteristics, FSH, and inhibin B levels to measure fertility levels. RESULTS: Data were extracted from five studies featuring 1344 patients. 6 months post-ABVD saw marked deterioration in sperm count, further reduced by more cycles (P = 0.05). Patients treated with BEACOPP rather than ABVD were more prone to oligospermia. Receiving fewer cycles of both regimens increased the likelihood of sperm production recovering. Patients treated with 6-8 cycles of BEACOPP did not recover spermiogenesis. CONCLUSIONS: ABVD and BEACOPP regimens significantly reduce fertility function to varying effects depending on treatment duration. ABVD temporarily causes significant reductions in male fertility, whereas BEACOPP's effects are more permanent. Therefore, clinicians should discuss fertility preservation with male patients receiving infertility-inducing gonadotoxic therapy. Further high-quality studies are required to more adequality describe the risk to fertility by chemotherapy.

Specific locus mutations induced in somatic cells of rats by orally and parenterally administered procarbazine.

A new test, the granuloma pouch assay, was used in detecting specific locus mutations in somatic cells of rats in vivo after the animals were treated orally and parenterally with procarbazine hydrochloride, an agent used in cancer chemotherapy. The results indicate that stable intermediates are formed in the body and distributed as proximate mutagens.

Human brain tumor transplantation into nude mice.

Seven human brain tumors were transplanted into the brains (6/7 takes) and subcutaneous tissues (7/7 takes) of athymic nude mice. Compared to experimental animal brain tumors, these tumors, taken directly from patients in the operating room and transplanted, grew more slowly in the mice; their growth rates following explant generally paralleled those in the patients. A rough correlation was seen between the degree of the tumor's malignancy and both successful take and rate of growth following explant. The tumors' growth rates increased during serial transplantation after explant. Two tumors developed into long-term serial lines; both came from gliosarcomas. Preliminary chemotherapy experiments with these two lines demonstrated different chemosensitivities. One line was very sensitive to the nitrosoureas and resistant to procarbazine; the other line was more sensitive to procarbazine than to the nitrosoureas. This model permits study of the biologic behavior of human brain tumors growing intracerebrally and subcutaneously in nude mice.

Influence of chemotherapeutic agents on chorionic gonadotropin-alpha subunit secretion in a human lung cancer cell line (ChaGo): discordance of cytotoxic and secretory effects.

Cells from cultures of ChaGo, a cell line of a human lung cancer that ectopically produces chorionic gonadotropin (hCG) and its alpha subunit (hCG-alpha) were exposed to five different cancer chemotherapeutic agents in vitro in separate experiments (one drug/expt). The control doubling time averaged 4 days, with molar biphasic secretory rates of hCG-alpha ranging from a high of 58.1 to a low of 10.5 pmoles/10(6) cells/24 hours. Drug concentrations were chosen to induce a 30-60% inhibition of cell replication over a period of 8-10 days. Neither methotrexate nor vincristine demonstrated major effects on extracellular hCG-alpha production, but each agent moderately depressed cell number and each produced major inhibition of intracellular protein synthesis. Procarbazine inhibited marker production only in slight excess of inhibition of cell growth and cell protein. Actinomycin D and mechlorethamine, however, had profound effects on inhibition of hCG-alpha production in excess of cell growth. Our results indicated that cancer chemotherapeutic agents have specific and differing effects on cell growth and cell protein on the one hand and marker production on the other. These data suggested a mechanism for certain cases of discordance between hormone production and clinical status.

Methylazoxyprocarbazine, the active metabolite responsible for the anticancer activity of procarbazine against L1210 leukemia.

Procarbazine is a 1,2-disubstituted hydrazine derivative that is used to treat human leukemias. The anticancer activity of procarbazine results from bioactivation to reactive intermediates. It is first oxidized to azoprocarbazine and further N-oxidized to a mixture of methylazoxyprocarbazine and benzylazoxyprocarbazine isomers. In this study the azoxyprocarbazine isomers were synthesized and purified. The cytotoxic effect of the metabolites on the L1210 murine leukemia cell line were then evaluated in vitro by use of a colorimetric assay using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide. The results of this study showed that the methylazoxyprocarbazine isomer was the most cytotoxic metabolite (IC50, 0.2 mM). The benzylazoxy isomer had an insignificant cytotoxic effect, and a mixture of the two isomers was intermediate in effectiveness. This assay, however, could not be used to determine the cytotoxicity of procarbazine since the drug itself (not the live cells) reduced the dye. A soft-agar clonogenic assay demonstrated that procarbazine was cytotoxic only at higher concentrations (IC50, 1.5 mM) than methylazoxyprocarbazine (IC50, 0.15 mM). The effect of procarbazine and its metabolites on the survival of L1210 tumor-bearing mice was determined, and methylazoxyprocarbazine was again the most effective compound. These studies demonstrate that the methylazoxyprocarbazine metabolite is probably the major cytotoxic intermediate involved in the mechanism of anticancer action of procarbazine.

Separate mechanisms for procarbazine spermatotoxicity and anticancer activity.

Procarbazine causes dose-dependent decreases in sperm count after a single i.p. injection in (C57BL/6 X DBA/2)F1 male mice. Two antioxidants, N-acetylcysteine and sodium ascorbate, administered with equimolar doses of procarbazine decreased the spermatotoxicity of procarbazine. At the highest doses of procarbazine (400 mg/kg) that caused a 56% decrease in sperm count, equimolar doses of N-acetylcysteine coadministered with procarbazine caused only a 17% decrease in sperm count, and equimolar doses of ascorbate coadministered with procarbazine caused only a 13% decrease in sperm count. Thus, protection against the spermatotoxic effects of procarbazine was demonstrated with either antioxidant. The effect of the antioxidants on the chemotherapeutic efficacy of procarbazine against murine L1210 leukemia was also assessed. Procarbazine at the highest dose (600 mg/kg) increased mean survival time of mice inoculated i.p. with 1 X 10(5) L1210 leukemia cells by 31%. Simultaneous administration of equimolar doses of either N-acetylcysteine or ascorbate given with procarbazine caused no change in the increased mean survival time of tumor-bearing mice. These results indicate a decrease in the toxicity of procarbazine when coadministered with antioxidants, via decreased spermatotoxicity without changing anticancer efficacy. The results also indicate that different mechanisms are involved in the spermatotoxicity and anticancer activity of procarbazine.

Accumulation of O6-methylguanine in human blood leukocyte DNA during exposure to procarbazine and its relationships with dose and repair.

O6-Methylguanine was measured by a competitive repair assay in blood leukocyte DNA of seven patients with Hodgkin's or non-Hodgkin's lymphoma during therapeutic exposure to procarbazine involving three daily p.o. doses (50 mg each) for 10 days (corresponding to 2.1 mg/kg/day for a 70-kg human). Adduct accumulation was observed in all seven cases, reaching levels up to 0.28 fmol/microgram of DNA (0.45 mumol/mol of guanine). In one individual, maximal levels of adduct were reached after 7 days of exposure, followed by a steady decline, whereas in all other individuals continuous accumulation was observed throughout the exposure period. In four individuals for which data were available for Day 11 (12 to 16 h after the final intake of procarbazine), decreased amounts of O6-methylguanine were observed relative to the last previous measurements. The accumulation of O6-methylguanine was linearly correlated (P less than 0.01) with the cumulative dose of procarbazine, with a slope of 0.011 fmol of O6-methylguanine/microgram of DNA per mg/kg of body weight or 2.68 x 10(-4) fmol of O6 methylguanine DNA per mg/m2. (Two h after the administration of single p.o. doses of 1 to 10 mg/kg of procarbazine to rats, O6-methylguanine formation in leukocyte DNA was just under half that in liver DNA and showed a linear relationship with dose with a slope of 0.017 fmol/microgram of DNA per mg/kg of body weight or 5.67 x 10(-4) fmol of O6-methylguanine/microgram of DNA per mg/m2. A negative correlation (P less than 0.05) between the rate of accumulation of O6-methylguanine in different individuals and lymphocyte O6-alkylguanine-DNA alkyltransferase (AGT) was observed, demonstrating a probable protective effect of AGT against the accumulation of O6-methylguanine during exposure to methylating agents. This observation supports the suggestion of a possible role of procarbazine-induced O6-methylguanine in the pathogenesis of acute nonlymphocytic leukemia appearing after treatment with chemotherapeutic protocols which include procarbazine, based on the finding of low lymphocyte AGT levels in patients with such therapy-related neoplastic disease (Sagher et al., Cancer Res., 48: 3084-3089, 1988). Lymphocyte AGT levels were mainly in the range of 5 to 10 fmol/micrograms of DNA and showed no consistent variation during procarbazine exposure.

Cytotoxicity and DNA damage caused by the azoxy metabolites of procarbazine in L1210 tumor cells.

Procarbazine, a chemotherapeutic hydrazine, is thought to be metabolized to an alkylating species similar to methyl carbonium ion by multistep reactions involving cytochrome P-450, monoamine oxidase, and cytosolic enzymes. The DNA-damaging and cytotoxic potential of procarbazine and its metabolites in murine L1210 leukemia tumor cells in vitro was determined using alkaline elution techniques and extrapolation of growth curves. Neither procarbazine nor any of the chemical degradation products (except for the aldehyde derivative at high concentrations) caused significant amounts of DNA strand breakage. The primary enzymatic oxidation product, azo-procarbazine, did not produce strand breakage. However, exposure of the cells to either of the two isomers of azoxy-procarbazine led to significant DNA damage and cytotoxicity. DNA damage included both single-strand breaks and alkali-labile sites. At equimolar concentrations, the azoxy 2 isomer of procarbazine caused 14 to 20 times more DNA damage than did the azoxy 1 metabolite. When cell growth is expressed as percentage survival of L1210 cells, the azoxy 2 isomer was approximately 7-fold more toxic than the azoxy 1 metabolite. The other metabolites tested showed little or no cytotoxicity. L1210 cells were shown to contain little or no cytochrome P-450 or monoamine oxidase activity, which may account for the lack of toxicity of the parent drug or the primary oxidative metabolite, azo-PCZ, to these cells. The conversion of procarbazine to the azoxy-procarbazine isomers in vivo must occur in cells which contain these enzymes, such as liver. However, the azoxy isomers of procarbazine were metabolized in L1210 cells, presumably leading to the DNA or cytotoxic damage observed.

Potentiation of the cytotoxic action of mafosfamide by N-isopropyl-p-formylbenzamide, a metabolite of procarbazine.

Several mouse aldehyde dehydrogenases catalyze the detoxification of aldophosphamide, the pivotal metabolite of the prodrugs cyclophosphamide, mafosfamide, and other oxazaphosphorines. N-Isopropyl-p-formylbenzamide, a major metabolite of procarbazine, was found to be an excellent substrate (Km = 0.84 microM) for at least one of these enzymes, namely, mouse aldehyde dehydrogenase-2. The Km for mouse aldehyde dehydrogenase-2-catalyzed detoxification of aldophosphamide is 16 microM. Thus, competition between N-isopropyl-p-formylbenzamide and aldophosphamide for the catalytic site on the enzyme should strongly favor the former, and the rate at which aldophosphamide is detoxified should be markedly retarded. Mouse L1210/OAP and P388/CLA leukemia cells are relatively insensitive to the oxazaphosphorines because they contain large amounts of mouse aldehyde dehydrogenase-2. As predicted, N-isopropyl-p-formylbenzamide markedly potentiated the cytotoxic action of mafosfamide against these cells. Mouse L1210/0 and P388/0 lack the enzyme. Again as expected, N-isopropyl-p-formylbenzamide essentially did not potentiate the cytotoxic action of mafosfamide against these cells. Certain mouse and human hematopoietic progenitor cells also contain an aldehyde dehydrogenase that catalyzes the detoxification of aldophosphamide, but the specific identity of this enzyme remains to be established. N-Isopropyl-p-formylbenzamide potentiated the cytotoxic action of mafosfamide against these cells as well. Clinically, procarbazine and the oxazaphosphorines are used to treat certain neoplastic diseases. Frequently, they are used in combination. Our findings demonstrate the potential for both desirable and undesirable drug interactions when these agents are used concurrently. Similar drug interactions can be expected when other substrates for, or inhibitors of, the relevant aldehyde dehydrogenases, e.g., chloramphenicol, chloral hydrate, and methyltetrazolethiol-containing cephalosporins, are co-administered with the oxazaphosphorines.

Testing the gonadal regression-cytoprotection hypothesis.

Germinal damage is an almost universal accompaniment of cancer treatment as the result of bystander damage to the testis from cytotoxic drugs and/or irradiation. Cancer treatment for the most common cancers of the reproductive age group in men has improved such that most are now treated with curative intent, and many others are treated with likelihood of prolonged survival, so that the preservation of fertility is an important component of posttreatment quality of life. This has led to the consideration of developing adjuvant treatments that may reduce the gonadal toxicity of cancer therapy. One dominant hypothesis has been based on the supposition that the immature testis was resistant to cytotoxin damage. Hence, if hormonal treatment were able to cause spermatogenic regression to an immature state via an effective withdrawal of gonadotrophin secretion, the testis might be maintained temporarily in a protected state during cytotoxin exposure. However, clinical studies have been disappointing but have also been unable to test the hypothesis definitively thus far, due to the inability to completely suppress gonadotrophin secretion. Similarly, experimental models have also given conflicting results and, at best, a modest cytoprotection. To definitively test this hypothesis experimentally, we used the fact that the functionally hpg mouse has complete gonadotrophin deficiency but can undergo the induction of full spermatogenesis by testosterone. Thus, if complete gonadotrophin deficiency were an advantage during cytotoxin exposure, then the hpg mouse should exhibit some degree of germinal protection against cytotoxin-induced damage. We therefore administered three different cytotoxins (200 mg/kg procarbazine, 9 mg/kg doxorubicin, 8 Gy of X irradiation) to produce a range of severity in testicular damage and mechanism of action to either phenotypically normal or hpg mice. Testis weight and homogenization-resistant spermatid numbers were measured to evaluate the potential protective effects on spermatogenesis. Although the three cytotoxins produced a range of severity of spermatogenic damage, there was no evidence of cytoprotection in the hpg mice that were completely gonadotrophin deficient at the time of treatment. These findings cast doubt on the validity of the hypothesis that spermatogenic regression via gonadotrophin withdrawal can protect the mouse testis against cytotoxin-mediated spermatogenic damage.

Risk of subsequent gastrointestinal cancer among childhood cancer survivors: A systematic review.

BACKGROUND: Childhood cancer survivors (CCS) are at increased risk of developing subsequent malignant neoplasms, including gastrointestinal (GI) cancer. We performed a systematic review to summarize all available literature on the risk of, risk factors for, and outcome after subsequent GI cancer among CCS. METHODS: A systematic search of the literature databases Medline/PubMed (1945-2014) and Embase (1947-2014) was performed to identify studies that consisted of ⩾1000 CCS and assessed incidence of or mortality from subsequent GI cancer as an outcome. RESULTS: A total of 45 studies were included. Studies that reported risk measures for subsequent GI cancer compared to the general population showed a 3.2 to 9.7-fold elevated risk in cohort studies including all childhood cancer types. Abdominal radiotherapy was associated with an increased risk of subsequent GI cancer in all four studies that assessed this risk. Survivors who had received procarbazine and platinum agents were also suggested to be at increased risk. CONCLUSION: Abdominal radiotherapy is a risk factor for developing a subsequent GI cancer. Few studies examined detailed treatment-related risk factors and most studies had small number of GI cancer cases. Therefore, no conclusions could be drawn on the effect of time since childhood cancer on GI cancer risk and on outcome after a subsequent GI cancer. Additional research is necessary to further explore risk factors for and outcome after a subsequent GI cancer, and to systematically evaluate the harms and benefits of GI screening among high-risk survivors in order to give sound screening recommendations.

The detection of mutants in mice by electrophoresis: results of a model induction experiment with procarbazine.

Male mice of the DBA/2J strain were treated with the mutagen procarbazine and mated with C57BL/6J females. Offspring and parents were then analyzed for electrophoretically expressed mutations. A control group, not mutagen treated, was also examined. Two mutants probably due to induction were identified, and several of spontaneous origin were also found.

Protection against procarbazine-induced testicular damage by GnRH-agonist and antiandrogen treatment in the rat.

Suppression of spermatogenesis in LBNF1 rats by treatment with the GnRH agonist Zoladex combined with the antiandrogen flutamide was evaluated in order to rapidly achieve protection of spermatogenic stem cells against procarbazine with clinically used drugs. Zoladex-flutamide treatment required 3 weeks to suppress the completion of spermatogenesis; only a small degree of suppression was observed with Zoladex alone. The suppression of spermatogenesis was reversible. In rats pretreated for 3 weeks with Zoladex-flutamide, the recovery of spermatogenesis at 9 weeks after a single injection of procarbazine as measured by testis weight, testicular sperm head counts, or a histological end point was significantly better than without hormonal pretreatment. Thus Zoladex-flutamide treatment enhanced the recovery of spermatogenesis from stem spermatogonia after procarbazine treatment in the rat and might be applicable to protect spermatogenesis in patients undergoing chemotherapy for cancer.

Relationship among hormonal treatments, suppression of spermatogenesis, and testicular protection from chemotherapy-induced damage.

To further elucidate the mechanism by which hormonal pretreatment protects the rat testis from damage by procarbazine, we investigated the relationship between the suppression of hormone levels and spermatogenesis and the recovery of spermatogenesis from stem spermatogonia. LBNF1 rats were implanted with capsules containing testosterone or testosterone plus estradiol. After hormone treatment, rats were injected with procarbazine, and recovery of spermatogenesis was assessed. Testosterone (2 cm) plus estradiol (0.5-cm) reduced serum LH levels causing intratesticular testosterone (ITT) to fall to 3% of control levels within 2 weeks, but testis weights and sperm head counts were not appreciably suppressed until 4 weeks. Two weeks' hormone pretreatment, only slightly enhanced spermatogenesis recovery, but 4 weeks markedly increased it. Testosterone (2 cm) alone produced slower suppression of spermatogenesis and less protection from procarbazine than did testosterone plus estradiol implants, despite equivalent suppression of LH and ITT. Long testosterone implants (24-cm) partially maintained ITT at 14% of control despite undetectable LH levels, prevented any decline in sperm counts, and nearly completely abrogated the protective effect of the hormone treatment. Protection appeared to be best correlated with the testis weight reduction by hormone treatment. Thus, recovery of spermatogenesis after chemotherapy is dependent on the degree of suppression of spermatogenesis caused by the reduction of ITT levels at the time of chemotherapy and likely involves cells, such as the Sertoli cells, that are both androgen-responsive and affected by the numbers of germ cells present.

Rapid protection of rat spermatogenic stem cells against procarbazine by treatment with a gonadotropin-releasing hormone antagonist (Nal-Glu) and an antiandrogen (flutamide).

GnRH antagonist (Nal-Glu) treatment combined with the antiandrogen flutamide was used to suppress rat spermatogenesis to achieve protection of spermatogonial stem cells against the anticancer drug procarbazine. Daily injections with Nal-Glu alone suppressed spermatogenesis in a dose-responsive manner. However, it was necessary to combine Nal-Glu (600 micrograms/kg.day) with flutamide at 20 mg/kg.day to decrease testicular weight in 2 weeks to less than 0.6 g, a level previously demonstrated sufficient to protect stem cells in our model system. The Nal-Glu-flutamide pretreatment suppressed serum gonadotropin levels and intratesticular testosterone levels (6% of control) and action, resulting in a reversible decrease in the number of late spermatids to 1% of control levels. When rats were given Nal-Glu-flutamide for 2 weeks before a 250 mg/kg dose of procarbazine, recovery of spermatogenesis, as measured by testis weight, testicular sperm head counts, and repopulation indexes, was significantly better than in control rats (no hormonal pretreatment). The protection achieved with Nal-Glu-flutamide was better than that achieved with 2 weeks of testosterone and estradiol treatment. The present results show that Nal-Glu-flutamide protects spermatogonial stem cells against procarbazine and suggest a method of hormonal pretreatment to achieve rapid and efficient protection of spermatogenesis in humans.

Cytostatic drugs are without significant effect on digitoxin plasma level and renal excretion.

In three patients with malignant lymphoma who received 0.5 mg digitoxin before and 24 hr after combination therapy with cyclophosphamide, Oncovin, procarbazine, and prednisone (COPP) or cyclophosphamide, Oncovin, and prednisone (COP), plasma glycoside concentrations and renal excretion were measured 0 to 168 hr after digitoxin and the areas under plasma concentration-time curves *(AUCs) were calculated. In 10 patients receiving 0.1 mg digitoxin, daily plasma glycoside concentration and daily renal excretion were measured before and after COPP, COP, or cyclophosphamide, Oncovin, cytosine-arabinoside, and prednisone (COAP) treatment schemes. In contrast to previous reports on digoxin, cytostatic drug therapy does not lead to a reduction in steady-state digitoxin plasma levels and daily renal excretion. During cytostatic therapy attainment of peak digitoxin level was delayed after a single dose, showing that the rate of digitoxin absorption was reduced, but that the AUCs and renal excretion of digitoxin (parameters of the extent of digitoxin absorption) were not diminished. Since the absorption rate is not clinically relevant in patients on long-term glycoside therapy, our results indicate that digitoxin is preferable to digoxin in such patients.