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PubMed2003

Program participation and physical activity maintenance after cardiac rehabilitation.

This study examined exercise maintenance among patients after completing cardiac rehabilitation. Subjects were men and women who had completed a Phase II Cardiac Rehabilitation Program approximately 12 months previously. Subjects were classified according to whether they had (a) never participated in a Phase III program (G-I) (N = 37), (b) enrolled and completed a Phase III program (G-II) (N = 30), or (c) were currently enrolled in a Phase III maintenance program (G-III) (N = 33). Subjects were significantly more likely to be participating in regular exercise if they had participated in a Phase III program (p < .05). Individuals in G-II and G-III engaged in more minutes of physical activity per week and were more likely to meet recommended levels of physical activity compared to G-1 subjects. G-1 individuals who had longer Phase II programs were more likely to maintain their exercise habits following graduation (p < .05). Results suggest that Phase III maintenance programs and longer Phase II participation improved exercise maintenance following rehabilitation.

Aftercare↗
PubMed1988

Tricyclic maintenance therapy in unipolar depression.

The risk of recurrence of depression must be balanced against the problems and risks of maintenance therapy. The goal of maintenance therapy is to prevent new episodes of depression. A review of the literature reveals that the existing data does not provide sufficient evidence to demonstrate the usefulness of tricyclic maintenance therapy. Nonetheless, it would be premature to conclude that this type of treatment is not useful. Further studies of maintenance therapy are indicated and should include a continuation period of at least 16 weeks during which patients are symptom free (that is, Global Assessment Scale 71 or more). In the interim, each patient should be evaluated individually to determine the optimum duration of treatment.

Antidepressive Agents, Tricyclic↗
PubMed2006

A review of the evidence for the use of antipsychotics in the maintenance treatment of bipolar disorders.

Antipsychotic agents have long had a place in the clinical treatment of bipolar disorder, in both acute and maintenance phases. Recent clinical research conducted with the new generation of antipsychotic agents has contributed enormously to the data available on antipsychotic agents in bipolar disorder. Even now, however, the clinical trial data relates principally to the short-term treatment of acute mania. With the exception of recent data generated during the clinical trial programme for olanzapine, studies of maintenance treatment, conducted with antipsychotic agents, both established and newly-introduced, have generally been small and prone to methodological weakness. As a result, many important clinical questions, concerning the utility of antipsychotic agents in bipolar maintenance, can not be answered by reference to the data. Taken together, the findings of the clinical trials in bipolar maintenance, conducted with antipsychotic agents other than olanzapine, can be regarded only as tentative. As was conducted with olanzapine, larger, more rigorously designed studies are required to provide definitive evidence of efficacy in longer-term treatment. Due to the logistical complexity and expense of these sorts of study, it is likely that, for many antipsychotic agents with a potential role in long-term treatment in bipolar disorder, the definitive studies will never be undertaken.

Adverse Drug Reaction Reporting Systems↗
PubMed2002

Management of meningitis in children with oral fluid restriction or intravenous fluid at maintenance volumes: a randomised trial.

A multi-centre randomised open trial was done to determine whether moderate oral fluid restriction or intravenous fluid at full maintenance volumes would result in a better outcome for children with bacterial meningitis in Papua New Guinea, and what clinical signs could guide fluid management. Children with clinical signs and cerebrospinal fluid suggestive of bacterial meningitis received either breast milk by nasogastric tube at 60% of normal maintenance volumes (n = 172) or intravenous half-normal saline and 5% dextrose at 100% of normal maintenance volumes (n = 174) for the 1st 48 hrs of treatment. An adverse outcome was death or severe neurological sequelae, and a good outcome was defined as intact survival or survival with at worst mild-to-moderate neurological sequelae. The probability of an adverse outcome was 24.7% in the intravenous group and 33.1% in the oral-restricted group, but the difference was not statistically significant (RR 0.75, 0.53-1.04, p = 0.08). Sunken eyes or reduced skin turgor at presentation were risk factors for an adverse outcome (OR 5.70, 95% CI 2.87-11.29) and were most strongly associated with adverse outcome in the fluid-restricted group. Eyelid oedema during treatment was also a risk factor for an adverse outcome (OR 2.54, 95% CI 1.36-4.75) and eyelid oedema was much more common in the intravenous group (26%) than in the restricted group (5%). For many children with bacterial meningitis in less developed countries, moderate fluid restriction is unnecessary and will be harmful; a normal state of hydration should be achieved but over-hydration should be avoided. Giving 100% of normal maintenance fluids, especially with intravenous hypotonic fluid, will lead to oedema in up to one quarter of children with bacterial meningitis. If additional intravenous fluids are required for children with meningitis, an isotonic solution should be used.

Child↗
PubMed2003

Thioguanine offers no advantage over mercaptopurine in maintenance treatment of childhood ALL: results of the randomized trial COALL-92.

The German cooperative study group for childhood acute lymphoblastic leukemia (COALL-92) was designed to examine the clinical effectiveness of thioguanine (TG) versus mercaptopurine (MP) in maintenance treatment of childhood acute lymphoblastic leukemia (ALL) in a randomized multicenter trial. TG and MP are prodrugs and have to be converted intracellularly to 6-thioguanine nucleotides (TGNs) for cytostatic activity. TG is converted into TGN in fewer steps and has been shown to be more cytotoxic in equimolar doses in vitro compared with 6-MP. Therefore, a higher effectiveness of TG in maintenance treatment was postulated. Of 521 patients enrolled into the protocol, 474 were randomized to receive either MP or TG during maintenance therapy in a daily oral dose. After a median observation time of 6.6 years, the probability of event-free survival was 79% +/- 3% for the MP group (238 children) and 78% +/- 3% in the TG group (236 patients). In spite of TGN levels, exceeding those of the MP group 7 times, treatment with TG did not improve the outcome but was more complicated to handle due to a specific toxicity profile of prolonged myelosuppression with marked thrombocytopenia. Therefore, MP should remain the preferred drug for maintenance treatment of ALL, unless other studies demonstrate superiority of TG in larger trials or selected patient groups.

Administration, Oral↗
PubMed2006

Maintenance therapy with rituximab leads to a significant prolongation of response duration after salvage therapy with a combination of rituximab, fludarabine, cyclophosphamide, and mitoxantrone (R-FCM) in patients with recurring and refractory follicular and mantle cell lymphomas: Results of a prospective randomized study of the German Low Grade Lymphoma Study Group (GLSG).

In follicular lymphoma (FL) and mantle cell lymphoma (MCL) the monoclonal antibody rituximab (R) improves the prognosis when combined with chemotherapy. The present study investigated R-maintenance after R-chemotherapy. Patients with recurring or refractory FL and MCL were randomized to 4 courses of fludarabine, cyclophosphamide, and mitoxantrone (FCM) alone or combined with R (R-FCM). Responding patients underwent a second randomization for R-maintenance comprising 2 further courses of 4-times-weekly doses of R after 3 and 9 months. The first randomization was stopped after 147 patients, when R-FCM revealed a significantly better outcome. All subsequent patients received R-FCM. Of the 176 patients who are currently evaluable (as of October 2005), 138 received R-FCM for remission induction. Response duration was significantly prolonged by R-maintenance after R-FCM, with the median not being reached in this evaluation versus an estimated median of 16 months (P = .001). This beneficial effect was also observed when analyzing FL (P = .035) and MCL (P = .049) separately. Hence, R-maintenance is effective after salvage with R-chemotherapy and significantly prolongs response duration in patients with recurring or refractory FL or MCL.

Adult↗
PubMed2006

A pilot, prospective evaluation of a novel alternative for maintenance therapy of breast cancer-associated lymphedema [ISRCTN76522412].

BACKGROUND: Prospective investigations of complete decongestive lymphatic physiotherapy (CDPT), including manual lymphatic drainage (MLD), have validated the efficacy of these interventions for the initial reduction of edema and long-term maintenance of limb volume in lymphedema. However, CDPT demands substantial time and effort from patients to maintain these benefits; the treatments are not always well-accepted, and patients may suffer from a deterioration in quality-of-life or a time-dependent loss of initial treatment benefits. A new device designed for home use by the patient, the Flexitouch, has been developed to mechanically simulate MLD. We have undertaken a prospective, randomized, crossover study of the efficacy of the Flexitouch, when compared to massage, in the self-administered maintenance therapy of lymphedema. METHODS: A prospective, randomized, crossover study of maintenance therapy was performed in 10 patients with unilateral breast cancer-associated lymphedema of the arm. Each observation phase included self-administered treatment with the Flexitouch or massage, 1 hour daily for 14 days, respectively, followed by crossover to the alternate treatment phase. Each treatment phase was preceded by a 1 week treatment washout, with use of garment only. The sequence of treatment was randomly assigned. The potential impact of treatment modality on quality of life was assessed with serial administration of the SF-36. RESULTS: Statistical analysis disclosed that the order of treatment had no outcome influence, permitting 10 comparisons within each treatment group. Post-treatment arm volume reduced significantly after the Flexitouch, but not after self-administered massage. The patients' mean weight decreased significantly with Flexitouch use, but not with massage. The Flexitouch device was apparently well-tolerated and accepted by patients. Serial SF-36 administration showed no deterioration in physical or psychosocial scores compared to baseline measurements; there were no statistical differences in scores when the two treatment modalities were compared. CONCLUSION: This short-term prospective evaluation of the Flexitouch suggests that the device may provide better maintenance edema control than self-adiminstered massage in breast cancer-associated lymphedema. The apparent ease of use and reliability of response to the device suggest that further broad-scale testing is warranted.

Aged↗
PubMed2006

Attitudes and actions of asthma patients on regular maintenance therapy: the INSPIRE study.

BACKGROUND: This study examined the attitudes and actions of 3415 physician-recruited adults aged > or = 16 years with asthma in eleven countries who were prescribed regular maintenance therapy with inhaled corticosteroids or inhaled corticosteroids plus long-acting beta2-agonists. METHODS: Structured interviews were conducted to assess medication use, asthma control, and patients' ability to recognise and self-manage worsening asthma. RESULTS: Despite being prescribed regular maintenance therapy, 74% of patients used short-acting beta2-agonists daily and 51% were classified by the Asthma Control Questionnaire as having uncontrolled asthma. Even patients with well-controlled asthma reported an average of 6 worsenings/year. The mean period from the onset to the peak symptoms of a worsening was 5.1 days. Although most patients recognised the early signs of worsenings, the most common response was to increase short-acting beta2-agonist use; inhaled corticosteroids were increased to a lesser extent at the peak of a worsening. CONCLUSION: Previous studies of this nature have also reported considerable patient morbidity, but in those studies approximately three-quarters of patients were not receiving regular maintenance therapy and not all had a physician-confirmed diagnosis of asthma. This study shows that patients with asthma receiving regular maintenance therapy still have high levels of inadequately controlled asthma. The study also shows that patients recognise deteriorating asthma control and adjust their medication during episodes of worsening. However, they often adjust treatment in an inappropriate manner, which represents a window of missed opportunity.

Administration, Inhalation↗
PubMed2006

Dietary and physical activity behaviors among adults successful at weight loss maintenance.

BACKGROUND: There is limited population-based data on behavioral factors found to be important for successful weight loss maintenance among adults. METHODS: Data from the 2004 Styles surveys, mailed to U.S. adults aged > or = 18 years were used to examine the difference in selected weight loss strategies and attitudes among persons who reported successful weight loss attempts (lost weight and able to keep it off) and persons who were not successful (previous attempts to lose weight were unsuccessful or they could not keep the lost weight off). Behaviors examined included modification of diet, leisure-time and sports activities, and self-monitoring, and barriers to weight management. RESULTS: Among adults who reported losing weight or trying to lose weight, 31.0% had been successful at both losing weight and maintenance after weight loss. Successful weight loss status differed by sex, age, and current weight status. Assessment of reported weight loss strategies, found that exercising > or = 30 minutes/day and adding physical activity to daily life were significantly higher among successful versus unsuccessful weight losers. Individuals who were successful at weight loss and maintenance were less likely to use over-the-counter diet products than those who were unsuccessful at weight loss. Significantly more successful versus unsuccessful weight losers reported that on most days of the week they planned meals (35.9% vs. 24.9%), tracked calories (17.7% vs. 8.8%), tracked fat (16.4% vs. 6.6%), and measured food on plate (15.9% vs. 6.7%). Successful losers were also more likely to weigh themselves daily (20.3% vs. 11.0%). There were a significantly higher proportion of successful losers who reported lifting weights (19.0%) versus unsuccessful (10.9%). The odds of being a successful weight loser were 48%-76% lower for those reporting exercise weight control barriers were influencing factors (e.g., no time, too tired to exercise, no one to exercise with, too hard to maintain exercise routine) compared to those who reported little or no influence of exercise; similarly, the odds were 48-64% lower for those who found certain dietary barriers to be influential (e.g., eat away from home too often, diet/health food costs too much). CONCLUSION: Self-monitoring strategies such as weighing oneself, planning meals, tracking fat and calories, exercising 30 or more minutes daily, and/or adding physical activity to daily routine may be important in successful weight loss maintenance. Leisure-time activities such as lifting weights or cooking/baking for fun are common strategies reported by those who were successful weight losers.

Journal Article↗
PubMed1983

The use of different induction and maintenance chemotherapy regimens for the treatment of advanced yolk sac tumors.

Four children with yolk sac tumor were treated with an aggressive combination chemotherapy program. Three children had presacral primary tumors, one having pulmonary metastases, and one had a testicular primary tumor with pulmonary metastases. Three children were treated when they had measurable disease, and one had no measurable disease. The chemotherapy program consisted of a 6-wk induction period with vincristine (VCR), cis-diamminedichloroplatinum (DDP), and bleomycin. Maintenance therapy consisted of VCR, actinomycin D, and cyclophosphamide (cytoxan) every 3-4 wk as tolerated. Treatment was discontinued after 12 mo of complete remission. All three patients with evaluable disease had a partial response (PR) to induction therapy. Two underwent surgical exploration following induction therapy, one a laparotomy and the other a thoracotomy, and were found to have only scar tissue at the sites of presumed residual disease. The third child with measurable disease progressed to a clinical complete response (CR) during maintenance therapy. Two patients have had no evidence of disease (NED) for 42+ and 41+ mo since starting therapy (28+ and 27+ mo since completing treatment). Two patients are NED 11+ and 7+ mo since starting therapy and remain on treatment. We have encountered no significant renal or pulmonary toxicity, and there have been only two hospitalizations during maintenance therapy for fever and neutropenia. These preliminary results employing different induction and maintenance chemotherapy programs and planned second-look surgical intervention appear encouraging.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Intensified induction and consolidation with or without maintenance chemotherapy for acute myeloid leukemia (AML): two multicenter studies of the German AML Cooperative Group.

In two multicenter trials, a total of 576 patients with acute myeloid leukemia (AML) were treated and found to be evaluable. Two hundred forty-two patients were in a 1978 pilot study and 334 patients were in a 1982 randomized study. Ages were between 15 and 78 years (median, 48). The uniform remission induction therapy in both studies consisted of one to two courses of a 9-day combination of 6-thioguanine (TG) with cytosine arabinoside (ARA-C) and daunorubicin (DNR) [TAD9]. The timing and sequencing of TAD9 was designed according to cell kinetic effects of ARA-C. A complete remission (CR) was achieved in 65% (70% and 61%, respectively) of patients within a median of 33 days, and in 68% of responders after only one course. The CR rate in patients 60 to 78 years of age was 51% (66% and 39%, respectively). In the 1978 pilot study, different protocols of post-remission treatment were applied at the different centers: monthly 5-day maintenance, TAD9 consolidation, both consolidation and maintenance, or no further therapy. The group receiving treatment during CR showed 24% probability of remissions at 4 years v 0% probability of remissions in the untreated group. Between the different post-remission protocols, no significant differences were observed. Remission duration was not influenced by age, WBC, or morphologic cell type, but was longer in patients achieving CR within 30 days (P = .017). In the subsequent 1982 study, 145 patients in CR were randomized for TAD9 consolidation with or without monthly maintenance. The updated life-table analysis revealed a predicted rate of continuous remission at 2 1/2 years of 30% for the maintenance and 17% for the nonmaintenance arm (P = .003). These results of response and remission duration in adult patients of all ages support the validity of intensified induction therapy and of consequent myelosuppressive treatment in remission.

Actuarial Analysis↗
PubMed1987

A prospective randomized trial of maintenance versus nonmaintenance intravesical bacillus Calmette-Guérin therapy of superficial bladder cancer.

Between August 1981 and July 1984, 93 patients with polychronotopic superficial papillary carcinoma (Ta and/or T1), flat carcinoma in situ (Tis), or concomitant superficial papillary and in situ bladder carcinoma were entered into a prospective randomized trial of maintenance v nonmaintenance intravesical bacillus Calmette-Guérin (BCG) therapy. Forty-six patients who received BCG weekly for 6 weeks were compared with 47 patients receiving the six-weekly doses of BCG plus monthly BCG for 2 years. Both groups were evaluated every 3 months by cytology, cystoscopy, and biopsy. A significant reduction in the number of recurrent tumors per patient-month was demonstrated for both groups (P less than .0001); however, the difference in reduction of tumors between the two groups was not significant. Additionally, patients receiving maintenance and nonmaintenance therapy had similar tumor recurrence and progression rates. These results indicate that monthly maintenance BCG does not prevent, delay, or reduce tumor recurrence or progression observed with the 6-week regimen. Maintenance BCG was associated with increased local toxicity, primarily dysuria, frequency, and urgency. Dosage reduction was required in 22 of 47 patients (46.8%). When the data were subjected to multivariate analysis, the presence or absence of tumor following induction BCG and PPD skin test results were found to be significant variables. Controlling for either the presence or absence of tumor following induction BCG, tumor recurrence and progression rates were not significantly different for the two treatment groups. However, the absence of tumor after induction BCG was associated with a longer disease-free duration (P = .00001) and time to progression (P = .095). Patients with a reactive tuberculin skin test before and after induction BCG had significantly less tumor recurrences than patients with different PPD skin tests results (P = .02). Tumor progression was not related to tuberculin skin testing.

BCG Vaccine↗
PubMed1988

Maintenance chemotherapy prolongs remission duration in adult acute nonlymphocytic leukemia.

The value of maintenance therapy after the achievement of complete remission in adult acute nonlymphocytic leukemia (ANLL) has never been clearly established. A randomized Eastern Cooperative Oncology Group (ECOG) study of postremission therapy compared outcomes in patients who received no further therapy to those administered long-term maintenance chemotherapy. Adverse results in the group administered no further therapy led to early termination of this trial after only 51 patients were randomized. Patients receiving no postremission therapy experienced significantly inferior remission durations (P = .002) compared with patients receiving maintenance therapy. All 26 patients in the group administered no postremission therapy have relapsed, with a median duration of remission of 4.1 months. In contrast, four of 25 patients (16%) who received maintenance therapy remain disease free, with a median duration of remission of 8.1 months.

Acute Disease↗
PubMed1989

Three versus five years of maintenance therapy are equivalent in childhood acute lymphoblastic leukemia: a report from the Childrens Cancer Study Group.

Childrens Cancer Study Group protocol 141 (CCG-141), a randomized trial, was designed in part to compare 3 v 5 years of maintenance therapy, to evaluate the role of late reinduction, and to identify factors that predict relapse after 3 years of continuous complete remission (CCR) in acute lymphoblastic leukemia (ALL). Of 880 patients entered on study, 827 (94%) achieved complete remission and 499 (56.7%) were in CCR after 3 years of maintenance therapy. Boys were required to have negative testicular biopsies before randomization. A total of 481 patients were eligible for the duration of therapy phase of the study. Of the 310 (64.4%) randomly assigned patients, 101 were entered on regimen A: discontinue therapy; 105 on regimen B: reinduction for 4 weeks, then discontinue therapy; and 104 on regimen C: continue maintenance therapy for 2 more years, then discontinue. After a median follow-up of over 72 months, no significant differences in disease-free survival (DFS) or survival were noted in the three regimens. At 6 years from randomization, 93.0%, 89.1%, and 89.1% of patients on regimens A, B, and C, respectively, remained in CCR. Isolated CNS or overt testicular relapses were not significantly different in any of the study regimens. Isolated testicular relapse after a negative biopsy occurred in only two of 137 randomized males (1.5%). DFS (P = .10) and survival (P = .83) were not significantly different for all boys and girls randomized to regimens A, B, or C. The relapse rate was higher in boys than in girls randomized to discontinue therapy (11% v 4%), but the difference was not statistically significant (P = .14). Except for the presence of occult testicular leukemia (TL) in males, no other factors were identified that predicted for adverse events after 3 years of CCR. We conclude that prolongation of maintenance therapy beyond 3 years does not improve survival or decrease the risk of relapse.

Adolescent↗
PubMed1998

Maintenance of remission with human recombinant interferon alfa-2a in patients with stages III and IV low-grade malignant non-Hodgkin's lymphoma. European Organization for Research and Treatment of Cancer Lymphoma Cooperative Group.

PURPOSE: Interferon alfa has shown significant activity in patients with low-grade malignant non-Hodgkin's lymphoma (NHL). In 1985, we initiated a prospective randomized study in which the potential benefit of interferon alfa given as maintenance treatment was investigated after tumor load reduction was achieved with chemoradiotherapy in patients with advanced low-grade malignant non-Hodgkin's lymphoma. PATIENTS AND METHODS: The study involved 347 patients with stage III or IV disease, 315 satisfying the eligibility criteria. All were treated with a regimen of cyclophosphamide, vincristine, and prednisone (CVP) given every 3 weeks for eight cycles. Thereafter, patients were eligible for iceberg irradiation. Finally, all patients were completely restaged, and responding and stable-disease patients were then randomized, 122 to interferon alfa-2a maintenance, 3 million U three times weekly for 1 year; and 120 to no further treatment. RESULTS: Seventy-nine percent of the patients response to CVP, ie, 45% complete remissions (CR) and 34% partial remissions (PR). In the group of randomized patients, the response rate after CVP plus or minus radiotherapy was 90%. As compared with control patients, patients in the interferon (IFN) maintenance group had a tendency toward a prolonged time to progression (TTP) (median, 132 v 87 weeks; P = .054, adjusted for response to CVP). However, overall survival was similar in both groups. Interferon was well tolerated. The median dose of IFN actually received corresponded to 90% of the planned cumulative dose. The treatment had to be stopped because of toxicity in 16 patients (15% of the patients in whom IFN was started). CONCLUSION: Interferon maintenance treatment in the phase of minimal residual disease of patients with advanced low-grade malignant NHL increased TTP at the borderline of statistical significance, without remarkable toxicity. However, overall survival was not influenced.

Adult↗
PubMed2006

Rituximab-CHOP versus CHOP alone or with maintenance rituximab in older patients with diffuse large B-cell lymphoma.

PURPOSE: To address early and late treatment failures in older patients with diffuse large B-cell lymphoma (DLBCL), we designed a two-stage randomized trial of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) versus rituximab plus CHOP (R-CHOP), with a second random assignment to maintenance rituximab (MR) or observation in responding patients. PATIENTS AND METHODS: Untreated DLBCL patients who were 60 years or older were randomly assigned to R-CHOP (n = 318) or CHOP (n = 314); 415 responders were randomly assigned to MR (n = 207) or observation (n = 208). The primary end point was failure-free survival (FFS). All P values were two sided. RESULTS: Three-year FFS rate was 53% for R-CHOP patients and 46% for CHOP patients (P = .04) at a median follow-up time of 3.5 years. Two-year FFS rate from second random assignment was 76% for MR compared with 61% for observation (P = .009). No significant differences in survival were seen according to induction or maintenance therapy. FFS was prolonged with MR after CHOP (P = .0004) but not after R-CHOP (P = .81) with 2-year FFS rates from second random assignment of 77%, 79%, 74%, and 45% for R-CHOP, R-CHOP + MR, CHOP + MR, and CHOP, respectively. In a secondary analysis excluding MR patients, R-CHOP alone reduced the risks of treatment failure (P = .003) and death (P = .05) compared with CHOP alone. CONCLUSION: Rituximab administered as induction or maintenance with CHOP chemotherapy significantly prolonged FFS in older DLBCL patients. After R-CHOP, no benefit was provided by MR. These results, which are consistent with an additive effect of rituximab, suggest that future studies could focus on maintenance strategies with novel agents as well as new induction therapies.

Age Factors↗
PubMed1999

Spermatogenesis without gonadotropins: maintenance has a lower testosterone threshold than initiation.

We showed previously that testosterone (T) alone could induce spermatogenesis and produce normally fertile spermatozoa in the absence of circulating gonadotropins. These studies used the hpg mouse, which is characterized by a congenital gonadotrophin deficiency due to a major deletion in the GnRH gene. Administering T by a subdermal implant of a SILASTIC brand tube impregnated with crystalline T showed that the androgenic requirement for full induction of spermatogenesis was a 1-cm length implant. Using this unique model of spermatogenesis without gonadotropins, we have now investigated the quantitative requirement for androgens to maintain spermatogenesis by testing the hypothesis that the androgenic threshold required for induction and maintenance of spermatogenesis are the same. Spermatogenesis was induced in homozygous hpg mice by T administration for 6 weeks. The first experiment determined the time-course of the regression of spermatogenesis after removal of the T-impregnated SILASTIC brand implant. Elongated spermatids were absent by 3 weeks and testicular weight regression was maximal by 4 weeks after androgen withdrawal. The second experiment examined the effects on maintenance of spermatogenesis of reducing the T dose. After full induction of spermatogenesis in homozygous hpg mice, the T implants were replaced with a range of smaller size T-impregnated SILASTIC brand implants for a further 4 weeks. All androgen-sensitive end-points (testis weight, tubular, and luminal diameters, round spermatids) were fully maintained with T implants of 0.06 cm and elongated spermatids with T implants of 0.25 cm. A further experiment showed that at very low T doses (0.06, 0.125 cm) the T effects observed at 4 weeks were maintained at 6 and 11 weeks duration. We conclude that the androgenic threshold to maintain spermatogenesis in the mouse is an order of magnitude lower than the threshold required for inducing spermatogenesis. This distinction suggests that the mechanism of action of testosterone in inducing spermatogenesis may involve regulation of a genetic switch to complete meiosis, whereas the maintenance involves a different locus of action. These findings suggest that further studies of androgen-dependent meiotic genes may be central to understanding the regulation and molecular basis of androgen-driven induction and maintenance of spermatogenesis.

Androgens↗
PubMed2001

Pharmacokinetics of a transdermal testosterone system in men with end stage renal disease receiving maintenance hemodialysis and healthy hypogonadal men.

Androgen deficiency is common in men with end stage renal disease (ESRD) on maintenance hemodialysis. Pharmacokinetics of transdermal testosterone in men receiving maintenance hemodialysis have not been studied. Our objective was to compare the pharmacokinetics of a transdermal testosterone system in healthy hypogonadal men and in men with ESRD on maintenance hemodialysis. We recruited 10 healthy hypogonadal men and 8 medically stable men on maintenance hemodialysis, 18--70 yr old, who had serum testosterone less than 300 ng/dL. After baseline sampling during a 24-h control period, two testosterone patches were applied daily for 28 days, to achieve a nominal delivery of 10-mg testosterone daily. In addition to single, pooled samples on days 7, 14, and 21, blood was drawn at 0, 2, 4, 6, 8, and 24 h on day 28 in healthy hypogonadal men and on an interdialytic day (day 21 or 28) as well as a dialysis day (day 21 or 28) in men on hemodialysis. On the dialysis day (day 21 or 28), serum free and total testosterone levels were measured hourly for 4 h before hemodialysis and for 4 h during hemodialysis. The dialysate was sampled for testosterone measurement. Baseline mean + SD total (92 +/- 82 vs. 222 +/- 50 ng/dL) and free (11 +/- 9 vs. 27 +/- 6 pg/mL) testosterone concentrations were lower in healthy hypogonadal men than in men with ESRD. After application of two testosterone patches, serum total and free testosterone concentrations rose into the midnormal range in both groups of men. Time-average, steady state (total testosterone, 506 +/- 88 vs. 516 +/- 86 ng/dL; free testosterone, 55 +/- 9 vs. 67 +/- 11 pg/mL), minimum, and maximum total and free testosterone concentrations were not significantly different between the two groups of men during treatment. Increments in total and free testosterone concentrations above baseline, baseline-subtracted areas under the total and free testosterone curves, and half-life of testosterone elimination (t(1/2), 2.1 +/- 0.1 vs. 2.1 +/- 0.2 h, P = not significant) were not significantly different between the two groups. In men receiving hemodialysis, time-average, steady state, and maximal total and free testosterone concentrations and baseline-subtracted areas under the total and free testosterone curves were higher on dialysis day than on an interdialytic day. On the day of hemodialysis, time-average total and free testosterone concentrations were not significantly different during the 4 h before or during hemodialysis. The amount of testosterone removed in the dialysate (8.4 +/- 1.6 microg during 4 h of hemodialysis) was small compared with the daily testosterone production rates in healthy young men. Serum dihydrotestosterone and estradiol concentrations increased into the normal male range and were not significantly different between the two groups. Percent suppression of LH was greater in men with ESRD than in healthy hypogonadal men. A regimen of two Testoderm TTS testosterone patches (Alza Corp., Mountain View, CA) daily can maintain serum concentrations of total and free testosterone and its metabolites dihydrotestosterone and estradiol in the midnormal range in healthy hypogonadal men and men on hemodialysis. The amount of testosterone cleared by hemodialysis is small, and hemodialysis does not significantly affect serum total and free testosterone concentrations in men treated with the testosterone patch.

Administration, Cutaneous↗