Pharmacology of pentoxifylline, a hemorheologic agent for the treatment of intermittent claudication

Therapeutic effects of pentoxifylline in propionic acid-induced autism symptoms in rat models: A behavioral, biochemical, and histopathological study

OBJECTIVE

The role of propionic acid (PPA) in eliciting behaviors analogous to autism in rat models is a documented phenomenon. This study examines the therapeutic implications of pentoxifylline-an agent traditionally used for peripheral vascular diseases-on these autism-like behaviors by modulating brain proteins and reducing pro-inflammatory cytokines like tumor necrosis factor-α (TNF-α) in a rat model.

METHODS

This research involved 30 male Wistar albino rats, which were divided into three distinct groups: a baseline control set, a PPA-treated cluster receiving a 250 mg/kg/day dose of PPA via intraperitoneal injection for a span of five days followed by saline orally, and a PPA group administered an oral dose of pentoxifylline at 300 mg/kg/day over 15 days. Subsequent to the treatment phase, euthanasia was carried out for the extraction of brain and blood samples, which were then analyzed for histopathological and biochemical markers.

RESULTS

The pentoxifylline-treated subjects demonstrated a significant mitigation in the manifestation of autistic-like behaviors, as assessed through a triad of social interaction tests. A noteworthy decline in TNF-α levels was observed, alongside a significant rise in the concentration of adenosine triphosphate and nerve growth factor in brain tissue (p < 0.05). Histopathological analysis underscored a reduction in oxidative stress and a significant preservation of neuronal cell types, specifically pyramidal neurons in the hippocampal CA1 and CA3 regions and Purkinje cells in the cerebellum (p < 0.001).

CONCLUSION

Pentoxifylline treatment has been found to effectively reduce the behavioral symptoms associated with autism, as well as biochemical and histopathological disruptions induced by PPA in rat models, highlighting its potential as a neurotherapeutic agent.

Immune responses in diabetic nephropathy: Pathogenic mechanisms and therapeutic target

Diabetic nephropathy (DN) is a chronic, inflammatory disease affecting millions of diabetic patients worldwide. DN is associated with proteinuria and progressive slowing of glomerular filtration, which often leads to end-stage kidney diseases. Due to the complexity of this metabolic disorder and lack of clarity about its pathogenesis, it is often more difficult to diagnose and treat than other kidney diseases. Recent studies have highlighted that the immune system can inadvertently contribute to DN pathogenesis. Cells involved in innate and adaptive immune responses can target the kidney due to increased expression of immune-related localization factors. Immune cells then activate a pro-inflammatory response involving the release of autocrine and paracrine factors, which further amplify inflammation and damage the kidney. Consequently, strategies to treat DN by targeting the immune responses are currently under study. In light of the steady rise in DN incidence, this timely review summarizes the latest findings about the role of the immune system in the pathogenesis of DN and discusses promising preclinical and clinical therapies.

Repurposing drugs for highly prevalent diseases: pentoxifylline, an old drug and a new opportunity for diabetic kidney disease

Diabetic kidney disease is one of the most frequent complications in patients with diabetes and constitutes a major cause of end-stage kidney disease. The prevalence of diabetic kidney disease continues to increase as a result of the growing epidemic of diabetes and obesity. Therefore, there is mounting urgency to design and optimize novel strategies and drugs that delay the progression of this pathology and contain this trend. The new approaches should go beyond the current therapy focussed on the control of traditional risk factors such as hyperglycaemia and hypertension. In this scenario, drug repurposing constitutes an economic and feasible approach based on the discovery of useful activities for old drugs. Pentoxifylline is a nonselective phosphodiesterase inhibitor currently indicated for peripheral artery disease. Clinical trials and meta-analyses have shown renoprotection secondary to anti-inflammatory and antifibrotic effects in diabetic patients treated with this old known drug, which makes pentoxifylline a candidate for repurposing in diabetic kidney disease.

Are the Protean Effects of Pentoxifylline in the Therapy of Diabetes and Its Complications Still Relevant?

Pentoxifylline (Px) has protean effects that can be utilized in the therapy of diabetes and its complications. There have been well-documented but often inconclusive improvements in peripheral arterial disease, foot ulcers, peripheral neuropathy, nephropathy, retinopathy, ischemic heart disease and cerebrovascular disease. In addition, non-alcoholic steatosis and steatohepatitis, which are closely associated with insulin resistance and type 2 diabetes, have been shown to improve with pentoxifylline. Surprisingly, pentoxifylline modestly improves insulin resistance through improvements in capillary blood flow as well as beta cell function and decreased hepatic glucose production. The therapeutic effects of pentoxifylline are complementary to the effects of drugs such as blockers of the renin-angiotensin-aldosterone system when utilized in the therapy of diabetic nephropathy.

Sensitizing the cytotoxic action of Docetaxel induced by Pentoxifylline in a PC3 prostate cancer cell line

BACKGROUND

Prostate cancer is one of the most frequently diagnosed types of cancers worldwide. In its initial period, the tumor is hormone-sensitive, but in advanced states, it evolves into a metastatic castration-resistant tumor. In this state, chemotherapy with taxanes such as Docetaxel (DTX) comprises the first line of treatment. However, the response is poor due to chemoresistance and toxicity. On the other hand, Pentoxifylline (PTX) is an unspecific inhibitor of phosphodiesterases; experimental, and clinically it has been described as sensitizing tumor cells to chemotherapy, increasing apoptosis and decreasing senescence. We study whether the PTX sensitizes prostate cancer cells to DTX for greater effectiveness.

METHODS

PC3 human prostate cancer cells were treated in vitro at different doses and times with PTX, DTX, or their combination. Viability was determined by the WST-1 assay by spectrophotometry, cell cycle progression, apoptosis, generic caspase activation and senescence by flow cytometry, DNA fragmentation and caspases-3, -8, and -9 activity by ELISA.

RESULTS

We found that PTX in PC3 human prostate cancer cells induces significant apoptosis per se and increases that generated by DTX, while at the same time it reduces the senescence caused by the chemotherapy and increases caspases-3,-8, and -9 activity in PTX + DTX-treated cells. Both treatments blocked the PC3 cell in the G1 phase.

CONCLUSIONS

Our results show that PTX sensitizes prostate tumor cells to apoptosis induced by DTX. Taken together, the results support the concept of chemotherapy with rational molecular bases.

Toxicity, Clastogenicity and Genotoxicity of Theophylline and Pentoxifylline in Mammalian Cells Cultured In Vitro

— As part of a developmental study on theophylline and pentoxifylline, these drugs were tested for possible cytotoxic, mutagenic and clastogenic effects on V79 hamster cells and human lymphocytes cultured in vitro. After the short-term treatment of V79 cells with theophylline and pentoxifylline, the cells were relatively resistant to the toxic effects of these methylxanthines. Generally, only high concentrations of theophylline or pentoxifylline had toxic effects on exposed V79 cells. Short-term treatment of V79 cells with theophylline or pentoxifylline did not induce 6-thioguanine resistant mutations in either the presence or absence of S9 fractions. However, in the absence of an S9 fraction, elevated levels of single-strand breaks in DNA were induced. Both methylxanthines caused clastogenic effects in human lymphocytes and hamster V79 cells after long-term exposure. We suggest that theophylline and pentoxifylline are clastogenic but not genotoxic, and that the molecular mechanism for the induction of single-strand breaks in DNA and the induction of chromosomal aberrations in cells treated with theophylline and pentoxifylline is not the induction of lesions in the DNA but the inhibition of DNA chain elongation.

Bronchopulmonary dysplasia: Pathophysiology and potential anti-inflammatory therapies

Inflammation of the preterm lungs is key to the pathogenesis of bronchopulmonary dysplasia (BPD), whether it arises as a consequence of intrauterine inflammation or postnatal respiratory management. This review explores steroidal and non-steroidal therapies for reducing neonatal pulmonary inflammation, aimed at treating or preventing BPD.

Pentoxifylline for Renal Protection in Diabetic Kidney Disease. A Model of Old Drugs for New Horizons

Diabetic kidney disease is one of the most relevant complications in diabetes mellitus patients, which constitutes the main cause of end-stage renal disease in the western world. Delaying the progression of this pathology requires new strategies that, in addition to the control of traditional risk factors (glycemia and blood pressure), specifically target the primary pathogenic mechanisms. Nowadays, inflammation is recognized as a critical novel pathogenic factor in the development and progression of renal injury in diabetes mellitus. Pentoxifylline is a nonspecific phosphodiesterase inhibitor with rheologic properties clinically used for more than 30 years in the treatment of peripheral vascular disease. In addition, this compound also exerts anti-inflammatory actions. In the context of diabetic kidney disease, pentoxifylline has shown significant antiproteinuric effects and a delay in the loss of estimated glomerular filtration rate, although at the present time there is no definitive evidence regarding renal outcomes. Moreover, recent studies have reported that this drug can be associated with a positive impact on new factors related to kidney health, such as Klotho. The use of pentoxifylline as renoprotective therapy for patients with diabetic kidney disease represents a new example of drug repositioning.

Effects of pentoxifylline on hemodynamic, hemorheological, and microcirculatory parameters in young SHRs during arterial hypertension development

The most common form of hypertension in young adults is isolated diastolic hypertension. Diastolic arterial pressure is determined by the total peripheral resistance and depends on both vascular hindrance and blood viscosity. The aim of our work was to study the efficiency of pentoxifylline (PTX) in young spontaneously hypertensive rats (SHRs) during the development of arterial hypertension. The effects of a treatment course with PTX (100 mg/kg/day p.o. for 6 weeks, from 5 to 11 weeks old) on the mean, systolic, and diastolic blood pressure (BP); stroke volume; cardiac output; total peripheral resistance (TPR); whole blood viscosity (BV); plasma viscosity; hematocrit; RBC aggregation and deformability; local cerebral blood flow (lCBF); and microvascularization of the visual cortex were studied in SHRs in comparison with control SHRs and Wistar Kyoto rats. PTX-treated SHRs had significantly lower systolic, diastolic, and mean BP (by 24%, 26%, and 15%, respectively) and BV (by 5-9%) and a higher erythrocyte deformability index (by 1.5-2%), lCBF (by 42%), average diameter of capillaries (by 11%), density of the capillary network (by 23%), and percentage of capillaries with a diameter of 3-7 µm in comparison with control SHRs. In conclusion, PTX exerted positive effects on the hemodynamic, hemorheological, and microcirculatory parameters in SHRs during the development of arterial hypertension.

Impact of different antithrombotics on the microcirculation and viability of perforator-based ischaemic skin flaps in a small animal model

The effects of antithrombotic drugs on random and free flap survival have been investigated in the past, but the experimental and clinical results are not in agreement. A perforator-based critical ischaemia model was used to evaluate the effects of different perioperatively administered pharmaceutical agents on tissue ischaemia and to assess the potential additional haemorheological or vasodilative effects of antithrombotics on flap microcirculation. Combined laser Doppler flowmetry and remission spectroscopy revealed an increase in certain microcirculation parameters in most groups in comparison with saline controls, and these changes correlated with flap survival. Clopidogrel and hirudin significantly improved the amount of viable flap tissue in comparison with controls, while unfractioned heparin had a negative effect on flap survival. Low molecular weight heparin, aspirin, pentoxifylline, and hydroxyethyl starch had no impact on the amount of viable flap tissue. A higher complication rate was observed in all experimental groups, but only clopidogrel had a negative impact on the flap viability. Our results add to the body of evidence supporting the conclusion that perioperative antithrombotic treatment improves flap survival. Clopidogrel and hirudin are effective pharmacological agents that significantly increased the viability of perforator-based skin flaps in rats, but at a higher risk of postoperative bleeding.

Pentoxifylline for the treatment of hemolytic anemia in a patient who developed recurrent gastrointestinal bleeding while on continuous-flow left ventricular assist device support

Pentoxifylline is an agent that improves red blood cell deformability (known as a hemorrheologic effect) and reduces blood viscosity. Here, we present a case of a patient with hemolytic anemia after continuous-flow left ventricular assist device (CF-LVAD) implantation that was successfully treated with pentoxifylline. Our case is a 64-year-old African American woman who was implanted with a HeartMate II device on August 6, 2010, as a bridge to transplant for end-stage heart failure. Her postoperative course was complicated by recurrent gastrointestinal bleeding and antiplatelet therapy was discontinued. On October 25, 2011, she was readmitted with anemia and hemoglobin of 6.6 mg/dl and no identifiable source of bleeding. Her lactate dehydrogenase (LDH) was 936 IU/L, indicating severe hemolysis. Due to her evidence of hemolytic anemia and her inability to tolerate antiplatelet therapy due to recurrent bleeding, she was discharged on pentoxifylline 400 mg thrice daily on October 27, 2011, with hemoglobin of 11.2 mg/dl after transfusion. After 60 days of pentoxifylline, her hemoglobin and LDH in clinic were 10.1 mg/dl and 223 IU/L, respectively. The patient was successfully bridged to transplant in June 2012. Additional analysis of pentoxifylline as a therapeutic modality to manage hemolytic anemia after CF-LVAD implantation may be warranted.

Pentoxifylline in preterm neonates: a systematic review

Sepsis, necrotizing enterocolitis (NEC), and chronic lung disease (CLD) in preterm neonates are associated with significant mortality and morbidity, including long-term neurodevelopmental impairment and socioeconomic burden. Safe and effective drugs for the prevention and treatment of these conditions are urgently needed. Pentoxifylline, a synthetic theobromine derivative, is a non-steroidal immunomodulating agent with unique hemorrheologic effects which has been used in a range of infectious, vascular, and inflammatory conditions in adults and children. The unique properties of pentoxifylline explain its potential benefits in preterm neonates with sepsis, NEC, and CLD, conditions characterized by activation of the inflammatory cytokine cascade, free radical toxicity, and impaired microcirculation. Pentoxifylline has anti-inflammatory properties resulting from inhibition of erythrocyte phosphodiesterase. It lowers blood viscosity and improves microcirculation and tissue perfusion. As a phosphodiesterase inhibitor, pentoxifylline downregulates pro-inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-6, and interferon-gamma. Methylxanthines, including caffeine, theophylline, and theobromine are relatively non-toxic drugs; of these, theobromine is the least toxic. Pentoxifylline-related significant adverse events are thus very rare. Unlike other methylxanthines, pentoxifylline does not have significant cardiac and bronchodilating effects at therapeutic doses. Although it is contraindicated in adults with recent cerebral hemorrhage due to its effect on platelets, red blood cells, and plasma fibrinogen levels, no significant adverse effects including thrombocytopenia and bleeding have been reported in critically ill preterm neonates with sepsis or NEC after treatment with pentoxifylline. Based on data from pilot randomized trials and observational studies, our systematic review suggests that pentoxifylline may reduce mortality and/or morbidity in preterm neonates with sepsis, NEC, and CLD. Results of experimental studies also indicate that pentoxifylline may potentially be beneficial in meconium aspiration syndrome and hypoxic ischemic encephalopathy. Given the substantial burden of sepsis, NEC, and CLD in high-risk preterm neonates, and the findings of this systematic review, pentoxifylline needs to be evaluated urgently as a preventative and therapeutic agent for these conditions in randomized controlled trials that can detect minimal clinically significant effect sizes. Further clinical and experimental studies are also necessary to evaluate whether pentoxifylline is safe and effective in meconium aspiration syndrome and hypoxic ischemic encephalopathy.

Pharmacologic therapy for intermittent claudication

Peripheral artery disease, defined as atherosclerosis in the lower extremities, affects nearly 8.5 million people in the United States. Due to the frequent asymptomatic manifestation of peripheral artery disease, diagnosis may be delayed and its true incidence underestimated. However, some patients may experience aching pain, numbness, weakness, or fatigue, a condition termed intermittent claudication. Peripheral atherosclerosis is associated with cardiovascular risk and physical impairment; therefore, treatment goals are aimed at decreasing cardiovascular risk, as well as improving quality of life. Little debate exists regarding the management of cardiovascular risk reduction, which consists of both antiplatelet therapy and risk factor modification. Despite recently published guidelines, the treatment of intermittent claudication is less well established and the management remains controversial and uncertain. Exercise remains the first-line therapy for intermittent claudication; however, pharmacologic treatment is often necessary. Although only two prescription drugs have been approved by the U.S. Food and Drug Administration for the treatment of intermittent claudication, several supplements and investigational agents have been evaluated. Therapeutic optimization should balance the anticipated improvements in quality of life with the potential safety risks.

A novel drug interaction between the quinolone antibiotic ciprofloxacin and a chiral metabolite of pentoxifylline

Pentoxifylline (PTX), a methylxanthine derivative, is metabolized to seven compounds in vivo, with metabolites 1 and 5 possessing biologic activity. Metabolite-1 is a chiral molecule and its S-enantiomer is selectively formed during PTX metabolism in vivo. We have developed a reproducible method of synthesizing a racemic mixture of the chiral metabolite-1 (M-1) of PTX. In this study, we examined the kinetics of racemic M-1 in mice compared to PTX. An interaction between PTX and the quinolone antibiotic ciprofloxacin has been demonstrated. A goal of this study was to determine if a similar interaction occurs between ciprofloxacin and M-1 in vivo. M-1 and PTX had similar absorption and elimination rates. M-1 was rapidly converted to PTX, while very little PTX was converted to M-1 in vivo. The peak concentration of biologically active drug (PTX+M-1) was 36% higher when M-1 was administered compared to PTX. Combination of ciprofloxacin and PTX significantly increased serum concentrations of both PTX and M-1 (2-fold) compared to controls. The combination of M-1 and ciprofloxacin significantly increased serum concentration of M-1 (3-fold) and PTX (2-fold). The ciprofloxacin/M-1 combination produced a significantly higher sera concentration of bioactive drug compared to all other groups suggesting that this combination may enhance the anti-fibrogenic effect.

Pharmacokinetics of pentoxifylline and its 5-hydroxyhexyl metabolite after oral and intravenous administration of pentoxifylline to healthy adult horses

OBJECTIVE

To determine serum pharmacokinetics of pentoxifylline and its 5-hydroxyhexyl metabolite in horses after administration of a single IV dose and after single and multiple oral doses.

ANIMALS

8 healthy adult horses.

PROCEDURES

A crossover study design was used with a washout period of 6 days between treatments. Treatments were IV administration of a single dose of pentoxifylline (8.5 mg/kg) and oral administration of generic sustained-release pentoxifylline (10 mg/kg, q 12 h, for 8 days). Blood samples were collected 0, 1, 3, 6, 12, 20, 30, and 45 minutes and 1, 2, 4, 6, 8, and 12 hours after IV administration. For oral administration, blood samples were collected 0, 0.25, 0.5, 0.75, 1, 2, 4, 8, and 12 hours after the first dose and 0, 0.25, 0.5, 0.75, 1, 2, 4, 8, 12, and 24 hours after the last dose.

RESULTS

Elimination of pentoxifylline was rapid after IV administration. After oral administration, pentoxifylline was rapidly absorbed and variably eliminated. Higher serum concentrations of pentoxifylline and apparent bioavailability were observed after oral administration of the first dose, compared with values after administration of the last dose on day 8 of treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, oral administration of 10 mg of pentoxifylline/kg results in serum concentrations equivalent to those observed for therapeutic doses of pentoxifylline in humans. Twice daily administration appears to be appropriate. However, serum concentrations of pentoxifylline appear to decrease with repeated dosing; thus, practitioners may consider increasing the dosage if clinical response diminishes with repeated administration.

Effect of combination therapy with systemic glucantime and pentoxifylline in the treatment of cutaneous leishmaniasis

INTRODUCTION

Cutaneous leishmaniasis is a common parasitic disease in Iran, especially in Isfahan. First line treatment for this disease is antimonial compounds; however, owing to the intermittent failure of this treatment and its significant side-effects alternative therapeutic measures have been advocated.

OBJECTIVE

Evaluating the efficacy of pentoxifylline plus glucantime in the treatment of cutaneous leishmaniasis.

METHODS

This double-blind, randomized, controlled clinical trial with simple sampling was performed on 64 patients with cutaneous leishmaniasis referred to the Skin Diseases & Leishmaniasis Research Center from an endemic foci of L. major in Isfahan. The patients randomly were divided into two groups. One group was treated with systemic Glucantime (20 mg pentavalent antimony/kg/day) combined with pentoxifylline (400 mg three times daily) and the other group were treated with Glucantime (20 mg pentavalent antimony/kg/day) plus placebo (three tablets daily) for 20 days. Follow up lasted 3 months. Response to treatment was grouped as complete improvement (lesions had been flattened, no induration, and epidermal creases had appeared), partial improvement (reduction in lesion size, but without the appearance of epidermal creases) and poor response (no reduction in lesion size).

RESULTS

Of 64 participants, 32 patients in the trial group and 31 patients in the control group were followed for 3 months. One patient in group B discontinued withdrew. After this time, complete improvement, partial improvement and poor response to treatment were 81.3%, 12.5% and 6.2% in the trial group and 51.6%, 29% and 19.4% in the control group, respectively. We also observed no adverse effect resulting from pentoxifylline.

DISCUSSION

The result obtained by two therapeutic methods indicates that combined therapy with Glucantime and pentoxifylline is more effective than Glucantime alone (P < 0.05).

Role of CYP1A2 and CYP2E1 in the pentoxifylline ciprofloxacin drug interaction

In this study the drug interaction between ciprofloxacin (CIPRO) and pentoxifylline (PTX) was investigated and the role of CYP1A2 in the drug interaction was determined with the aid of a selective CYP1A2 inhibitor, furafylline (FURA), and the Cyp1A2 knockout mouse. Serum concentrations of PTX (83.4+/-1 micromol/l) and metabolite-1 (M-1) (13.7+/-2.8 micromol/l) following a single injection of PTX (100 mg/kg i.p.) were significantly higher (P<0.05) in mice treated with CIPRO (25 mg/kg i.p. 9 days) compared to serum concentrations of PTX (46.3+/-0.5 micromol/l) and M-1 (6.4+/-1.1 micromol/l) in mice administered saline. Murine hepatic microsomes were incubated with PTX alone or the combination of PTX and CIPRO. The metabolism of PTX in the murine hepatic microsomes containing both CIPRO and PTX was significantly decreased compared to microsomes incubated with PTX alone, suggesting that CIPRO may inhibit the metabolism of PTX. To further clarify the role of CYP1A2 in the metabolism of PTX in mice, the effect of a selective CYP1A2 mechanism based inhibitor, FURA, on the metabolism of PTX was investigated and our results indicate that FURA inhibited metabolism of PTX. We then investigated PTX elimination in the Cyp1A2 knockout mouse. Blood levels of PTX were assessed at 2 and 20 min following a single injection of PTX (32 mg/kg i.v). Serum concentration of PTX was determined in Cyp1A2 knockout mice compared to Cyp1A2 wild type control mice. The serum concentration of PTX in Cyp1A2 wild type mice (n=9) was 22.2+/-3.2 micromol/l at 20 min following injection of PTX. The serum concentration of PTX in Cyp1A2 knockout mice (n=11) was significantly elevated at 20 min following injection of PTX compared to Cyp1A2 wild type mice. These results clearly indicate that inhibition of CYP1A2 catalytic activity that occurs in the Cyp1A2 knockout mice is sufficient to alter metabolism of PTX and result in markedly elevated levels in serum of Cyp1A2 knockout mice. The results of Western analysis in murine microsomes suggest that CYP1A2 protein levels were not altered by CIPRO indicating that CIPRO did not downregulate Cyp1A2. The results of Western analysis also indicated that CIPRO treatment increased CYP2E1 in mouse microsomes and the implications of these will be discussed.

American cutaneous leishmaniasis unresponsive to antimonial drugs: successful treatment using combination of N-methilglucamine antimoniate plus pentoxifylline

BACKGROUND

American cutaneous leishmaniasis is characterized by single or multiple ulcerations. Cytokines, among other factors, have been shown to influence lesion development and tumoral necrosis factor-alpha is a major cytokine implicated in pathogenesis of ulcers.

OBSERVATIONS

We tested oral pentoxifylline, a known tumoral necrosis factor-alpha inhibitor, at doses of 400 mg (2-3x/day), associated to N-methylglucamine antimoniate (15 mg/kg/day) in two patients with American cutaneous leishmaniasis unresponsive to antimonial drugs. We observed a satisfactory response with quick cure of skin lesions of these patients.

CONCLUSIONS

Our results suggest that oral pentoxifylline in association to N-methylglucamine antimoniate should be consider in refractory cutaneous leishmaniasis patients.

Pentoxifylline reverses oxidative mitochondrial defect in claudicating skeletal muscle

OBJECTIVE

Previous morphologic studies and phosphorus nuclear magnetic resonance spectroscopy (31P MRS) have suggested a primary mitochondrial defect in claudicating skeletal muscle. We hypothesized that pentoxifylline may alleviate this defect.

METHODS

The response of calf muscle bioenergetics to pentoxifylline was evaluated in 10 male, nondiabetic claudicants with 31P MRS and standard treadmill testing before and after 12 weeks of pentoxifylline therapy. Phosphocreatine (PCr) and adenosinodiphosphate (ADP) recovery rate constants, two very sensitive measures of oxidative mitochondrial function, were measured.

RESULTS

Seven of the 10 subjects had abnormal baseline PCr (<0.015 s(-1)) and ADP (<0.024 s(-1)) recovery rate constants. These 7 had significant improvement in mitochondrial function with pentoxifylline; their PCr recovery rate constants increased from 0.009 +/- 0.002 to 0.013 +/- 0.002 s(-1) (P = 0.013) and their ADP recovery rate constants increased from 0.015 +/- 0.002 to 0.022 +/- 0.002 s(-1) (P = 0.004). The remaining 3 patients had normal baseline constants and demonstrated no improvement after pentoxifylline therapy. Baseline PCr and ADP recovery rate constants inversely correlated with their corresponding percentage of improvement after pentoxifylline (P < 0.05). In addition the percentage of improvement in the PCr and ADP recovery rate constants correlated with the percentage of improvement in initial claudication distance and maximum walking capacity (P < 0.05).

CONCLUSIONS

Pentoxifylline improves the mitochondriopathy of claudicating muscle, producing the most improvement in limbs with the worse baseline mitochondrial function. These results point to a potential new mode of action for pentoxifylline in the treatment of claudication and identify a subgroup of patients with the best potential for improvement with treatment.

Comparative effects of cilostazol and other therapies for intermittent claudication

Many patients with peripheral arterial disease (PAD) have intermittent claudication or problems with ambulation and mobility. Exercise and smoking cessation are primary therapies for claudication, but drug treatment may provide additional benefit. The data supporting use of pentoxifylline for claudication are weak, and pentoxifylline is not generally accepted as efficacious. Cilostazol is a new drug for the treatment of claudication. It appears to modestly benefit walking ability and it has other potentially useful effects, including inhibition of platelet aggregation and beneficial effects on serum lipids. In a randomized, prospective, double-blind trial examining walking ability in patients with PAD with moderate-to-severe claudication, cilostazol was superior to both placebo and pentoxifylline.

Pentoxifylline potentiates nitric oxide production in interleukin-1beta-stimulated vascular smooth muscle cells through cyclic AMP-dependent protein kinase A pathway

In the present study, we observed that pentoxifylline (PTX) significantly augmented the nitric oxide (NO) production and the iNOS gene expression by interleukin-1beta (IL-1beta)-stimulated vascular smooth muscle cells (VSMCs). The enhancing effects of PTX on the IL-1beta-induced NO production was associated with an increased intracellular cyclic AMP (cAMP) levels, and the synergistic effects of PTX on the IL-1beta-induced NO production was blocked by cAMP-dependent protein kinase A (PKA) inhibitors. PKA inhibitors, KT5720 and H89, markedly decreased the augmented expression of iNOS gene whereas ODQ, a soluble guanylate cyclase inhibitor, did not affect the enhancing effect. In addition, the pretreatment with KT5720 or H89 abolished the increased translocation of the p65 subunit of NF-kappaB into the nucleus by PTX in the IL-1beta-stimulated VSMCs. These results suggest that enhancing effects of PTX on the iNOS gene expression in the IL-1beta-stimulated VSMCs is mediated predominantly through the activation of NF-kappaB via cAMP-dependent PKA pathway.

Pharmacokinetics of pentoxifylline in dogs after oral and intravenous administration

OBJECTIVE

To evaluate the pharmacokinetics of pentoxifylline (PTX) and its 5-hydroxyhexyl-metabolite, metabolite 1 (M1), in dogs after IV administration of a single dose and oral administration of multiple doses.

ANIMALS

7 sexually intact, female, mixed-breed dogs.

PROCEDURE

A crossover study design was used so that each of the dogs received all treatments in random order. A drug-free period of 5 days was allowed between treatments. Treatments included IV administration of a single dose of PTX (15 mg/kg of body weight), oral administration of PTX with food at a dosage of 15 mg/kg (q 8 h) for 5 days, and oral administration of PTX without food at a dosage of 15 mg/kg (q 8 h) for 5 days. Blood samples were taken at 0.25, 0.5, 1, 1.5, 2, 2.5, and 3 hours after the first and last dose of PTX was administered PO, and at 5, 10, 20, 40, 80, and 160 minutes after PTX was administered IV.

RESULTS

PTX was rapidly absorbed and eliminated after oral administration. Mean bioavailability after oral administration ranged from 15 to 32% among treatment groups and was not affected by the presence of food. Higher plasma PTX concentrations and apparent bioavailability were observed after oral administration of the first dose, compared with the last dose during the 5-day treatment regimens.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, oral administration of 15 mg of PTX/kg results in plasma concentrations similar to those produced by therapeutic doses in humans, and a three-times-a-day dosing regimen is the most appropriate.

Hemorheological changes and overproduction of cytokines from immune cells in mild to moderate dementia of the Alzheimer's type: adverse effects on cerebromicrovascular system

An association between hemorheological alterations (i.e., whole-blood and plasma hyperviscosity, reduced erythrocyte deformability, increased red cell aggregation, hyperfibrinogenemia and increased acute-phase protein levels) and the mild stage of senile dementia of the Alzheimer's type (DAT) was suggested in the present study. In particular, hyperfibrinogenemia and the increase of erytrhocyte aggregation were correlated with the increased generation and release of TNF-alpha and IFN-gamma (spontaneous release and IL-2-modulated release) from natural killer (NK) lymphocytes (CD16+, CD56+, CD3- cells) of patients with DAT; whereas a normal cytokine release from NK cells was found in healthy old subjects and in patients with vascular dementia (VaD). The in vitro and in vivo administration of the hemorheologic drug pentoxifylline (PTX) significantly reduced spontaneous and IL-2-modulated cytokine overproduction from NK cells (in vitro effects with 500 U/ml and 1000 U/ml/NK cells) and improved all the hemorheological parameters. Taken together, these data suggest that disturbances of cerebrovascular flow and of hemorheology could be considered a negative component related to the pathogenesis and progression of DAT neurodegeneration. The association between hemorheological changes and alterations of TNF-alpha and IFN-gamma release from NK may indicate a potential immunorheologic mechanism associated with cerebrovascular damage in DAT and could suggest the use of vascular protective drugs as support of the main pharmacological and non-pharmacological therapy of AD.

Procedure costs and outcomes associated with pharmacologic management of peripheral arterial disease in the Department of Defense

This study was undertaken to determine if differences existed between pharmacologic treatments of peripheral arterial disease (PAD) with respect to PAD-related costs and health care outcomes in the United States Department of Defense health care system. We performed a retrospective review of hospital and prescription data to explore the effects of at least 90 days of aspirin, pentoxifylline, papaverine, or dipyridamole on 4 PAD-related outcomes: number of PAD-related invasive procedures (INV), number of PAD-related examination procedures (EXM), number of PAD-related hospitalization days (HDAYS), and cost of PAD-related procedures (COST) during 5 years. A covariate representing the number of PAD-related hospitalizations before the study period was used to attempt to control for severity of disease state. General linear models were used in the analyses. A statistically significant difference was seen between treatment groups for a linear combination of INV, EXM, HDAYS, and COST when controlling for past PAD-related hospitalizations (P < 0.014). A statistically significant relationship existed between treatment groups and INV (P < 0.041). The pentoxifylline treatment group had a statistically significant higher covariate-adjusted mean INV compared with the aspirin treatment group (P < 0.043). Also, PAD-related past hospitalizations were significantly related to EXM (P < 0.006). Our results appear to support the use of aspirin as a preventive treatment in PAD compared with pentoxifylline or dipyridamole.

Multiple resistance modulators combined with carboplatin for resistant malignancies: a pilot study

BACKGROUND

Chemotherapy resistance is probably multifactorial; hence, we assessed the feasibility of adding to carboplatin 6 concurrent resistance modulators in 53 patients with resistant cancers.

METHODS

Pentoxifylline and dipyridamole were added to carboplatin 400 mg/m2 in cohort 1, and metronidazole was also given in cohort 2. Mannitol and saline were administered in each cohort with the theoretical objective of improving carboplatin delivery to tumors by reducing blood viscosity. Because of excessive toxicity in cohort 2, cohort 3 received the same modulators as in cohort 2 but with a reduced dose of carboplatin (200 mg/m2). Subsequent patients had the following drugs added to those in the previous cohort: novobiocin (cohort 4), tamoxifen (cohort 5), ketoconazole (cohort 6). Cohort 7 patients received the 6 cohort 6 modulators along with carboplatin 300 mg/m2.

RESULTS

Thrombocytopenia was excessive in early cohorts with a carboplatin dose of 400 mg/m2, but was minimal at lower doses. Other toxicity was generally tolerable and reversible, particularly at carboplatin doses < or = 300 mg/m2, although gastrointestinal and neurological toxicity tended to worsen as additional modulators were added. No major responses (but 4 minor responses) were seen in this patient population with heavily pretreated or primarily resistant cancers.

CONCLUSIONS

Acceptable doses for phase II studies are carboplatin 300 mg/m2, 20% mannitol 250 ml plus normal saline 500 ml over 1 hr prior to carboplatin, pentoxifylline 700 mg/m2/day p.o. from 3 days before carboplatin to cessation of therapy, dipyridamole 100 mg/m2 p.o. q6h x 6 days starting 24 hr before carboplatin, metronidazole (750 mg/m2 p.o. 12 hr and immediately before, and 24 hr after carboplatin; 250 mg/m2 suppository p.r. 12 hr and immediately before, and 6 and 24 hr after carboplatin; and 500 mg/m2 i.v. right after carboplatin), novobiocin 600 mg/m2 p.o. q12h x 6 days starting 24 hr before carboplatin, and tamoxifen 100 mg/m2/day plus ketoconazole 700 mg/m2/day x 3 days starting the day before carboplatin, with oral dexamethasone and ondansetron as antimetics.

Circadian variations in the pharmacokinetics of pentoxifylline in man

Optimization of therapy by chronopharmacology requires knowledge of rhythmic manifestations of disease activity and chronopharmacokinetic data of the drugs prescribed. Rhythmic functioning of the cardiovascular system in healthy and diseased subjects is manifested as circadian rhythms in blood pressure, cardiac output, heart rate, etc. The disposition of several cardiovascular drugs in man has been reported to be time-dependent. This study reports the effect of time of administration on the disposition of pentoxifylline. Twelve healthy volunteers were treated with 400 mg pentoxifylline orally at 0100, 0700, 1300 and 1900 h in a randomized crossover Latin-square design with a wash-out period of one week. Serum samples were analysed for unchanged pentoxifylline by HPLC. Pharmacokinetic parameters were calculated using a model-independent method. The mean values of various pharmacokinetic parameters after drug treatment at these times were, respectively: maximum plasma concentration (Cmax) 485+/-174, 646+/-175, 735+/-271 and 781+/-217 ng mL(-1); time to reach the maximum plasma concentration (Tmax) 1.90+/-0.39, 1.66+/-0.4, 1.31+/-0.41 and 1.32+/-0.44 h, mean residence time (MRT) 3.8+/-0.8, 2.9+/-0.5, 2.9+/-0.4 and 2.7+/-0.3 h, elimination half-life (t1/2) 1.93+/-0.86, 1.23+/-0.3, 1.39+/-0.3 and 1.23+/-0.18 h and volume of distribution at steady state (VdSS/f) 11991+/-4862, 8823+/-3484, 8275+/-2357 and 7063+/-1950 mL kg(-1). The mean Cmax value was significantly (P < 0.05) lower after drug administration at 0100 h than after other time-points whereas mean Tmax, MRT, VdSS/f and t1/2 values were significantly (P < 0.05) higher. These variations might be because of time-dependent changes in absorption and biliary excretion of pentoxifylline and should be borne in mind when designing sustained action dosage forms for the drug.

Pharmacological aspects of pentoxifylline with emphasis on its inhibitory actions on hepatic fibrogenesis

1. Pentoxifylline (PTX), a derivative of the methylxanthine theobromine, has been used for many years in the treatment of peripheral vascular diseases. Increased red blood cell flexibility, reduction of blood viscosity, and decreased potential of platelet aggregation are the basic actions of PTX, resulting in therapeutic benefits due to improved microcirculation and tissue oxygenation. 2. PTX's generally accepted mechanism of action is the inhibition of phosphodiesterases, leading to increased intracellular levels of cyclic adenosine monophosphate (cAMP). 3. A number of studies have shown PTX's effects on the cytokine network. The most relevant clinical results are the therapeutic benefits of PTX in attenuating the effects of tumor necrosis factor-alpha (TNF-alpha) in conditions such as septic shock. 4. PTX also has been found to exert antifibrogenic actions, using cultured fibroblasts or animal models of fibrosis, including liver fibrosis. 5. In hepatic stellate cell culture PTX has been shown to inhibit the basic reactions of liver fibrogenesis, being effective on cytokines and growth factors relevant in fibrogenesis of the liver, too. 6. Therefore, PTX might be an effective drug with few side effects in the treatment of liver fibrosis. Further clinical studies have to be done to establish the real therapeutic benefits of PTX in liver fibrosis and cirrhosis.

Human immunodeficiency virus type 1 vpr gene induces phenotypic effects similar to those of the DNA alkylating agent, nitrogen mustard

The product of the human immunodeficiency virus type 1 (HIV-1) vpr gene induces cell cycle arrest in the G2 phase of the cell cycle and is characterized by an accumulation of the hyperphosphorylated form of cdc2 kinase. This phenotype is similar to the effect of DNA-damaging agents, which can also cause cells to arrest at G2. We previously reported that Vpr mimicked some of the effects of a DNA alkylating agent known as nitrogen mustard (HN2). Here we extend these earlier observations by further comparing the activation state of cdc2 kinase, the kinetics of G2 arrest, and the ability to reverse the arrest with chemical compounds known as methylxanthines. Infection of cells synchronized in the G1 phase of the cell cycle with a pseudotyped HIV-1 resulted in arrest at G2 within 12 h postinfection, before the first mitosis. Similar to that induced by HN2, Vpr-induced arrest led to a decrease in cdc2 kinase activity. Vpr-mediated G2 arrest was alleviated by methylxanthines at concentrations similar to those needed to reverse the G2 arrest induced by HN2, and cells proceeded apparently normally through at least one complete cell cycle. These results are consistent with the hypothesis that Vpr induces G2 arrest through pathways that are similar to those utilized by DNA-damaging agents.

Cranial radiation and concomitant cisplatin and mitomycin-C plus resistance modulators for malignant gliomas

We studied the toxicity and efficacy of adding in sequence 4 resistance modulators to combination chemotherapy and radiotherapy in the treatment of glioblastoma multiforme and poor prognosis anaplastic astrocytomas. Patients received cisplatin plus mitomycin-C concurrently with and following 60 Gy of radiotherapy administered over 6 weeks. Resistance modulators were added in sequence to chemotherapy in each cohort of 6 patients as follows: metronidazole + pentoxifylline (cohort 1); + dipyridamole (cohort 2), + beta carotene (cohort 3). Central nervous system toxicity (which ranged from drowsiness to seizures and loss of consciousness) was frequent. The incidence of gastrointestinal symptoms was substantial, but was usually mild to moderate in severity. Three of 11 patients evaluable for response achieved a partial remission with treatment. The median survival duration for all patients was 26 weeks from initial diagnosis. The study was terminated prematurely because of significant toxicity (in this study as well as in parallel concurrent studies of similar design in other tumor types) and apparent lack of benefit.

Inhibition of fibroproliferation by pentoxifylline. Activity of metabolite-1 and lack of role of adenosine receptors

We have reported previously that pentoxifylline and adenosine decrease platelet-derived growth factor- (PDGF) stimulated fibroproliferation. To determine the role of adenosine receptors in the inhibition of fibroproliferation observed with pentoxifylline, we used a non-selective adenosine receptor antagonist, 8-phenyltheophylline, and specific A1 and A2 adenosine receptor antagonists. If the A2 receptor, which is present on fibroblasts, mediates the inhibition of fibroproliferation which occurs with pentoxifylline, then pretreatment of fibroblasts with receptor antagonists prior to the addition of pentoxifylline should prevent the action of pentoxifylline. The results indicated that pretreatment of fibroblasts with 8-phenyltheophylline (100 microM) did not alter the inhibitory effect of pentoxifylline on PDGF-stimulated fibroproliferation. These results argue against a mechanism involving inhibition of adenosine reuptake as the mechanism for pentoxifylline's effect in this system. 8-Phenyltheophylline also did not alter the effect of pentoxifylline on baseline proliferation, suggesting that these effects of pentoxifylline are not mediated by adenosine receptors. Pentoxifylline is metabolized to several metabolites including 1-(5-hydroxyhexyl)-3,7-dimethylxanthine (metabolite-1). Metabolite-1 significantly reduced PDGF-stimulated fibroproliferation and was as effective as pentoxifylline. The combination of pentoxifylline and metabolite-1 had an additive effect. Metabolite-1 and pentoxifylline also reduced baseline proliferation. Preincubation of fibroblasts with 8-phenyltheophylline did not prevent the inhibitory action of metabolite-1 on PDGF-stimulated proliferation or on basal proliferation of fibroblasts, suggesting that the action of metabolite-1 on fibroproliferation was not mediated by adenosine receptors. Results using A1 and A2 adenosine receptor antagonists further suggest that the effect of pentoxifylline was not mediated by adenosine receptors.

Synergistic and additive combinations of several antitumor drugs and other agents with the potent alkylating agent adozelesin

Adozelesin is a highly potent alkylating agent that undergoes binding in the minor groove of double-stranded DNA (ds-DNA) at A-T-rich sequences followed by covalent bonding with N-3 of adenine in preferred sequences. On the basis of its high-potency, broad-spectrum in vivo antitumor activity and its unique mechanism of action, adozelesin has entered clinical trial. We report herein the cytotoxicity for Chinese hamster ovary (CHO) cells of several agents, including antitumor drugs, combined with adozelesin. The additive, synergistic, or antagonistic nature of the combined drug effect was determined for most combinations using the median-effect principle. The results show that in experiments using DNA- and RNA-synthesis inhibitors, prior treatment with the DNA inhibitor aphidicolin did not affect the lethality of adozelesin. Therefore, ongoing DNA synthesis is not needed for adozelesin cytotoxicity. Combination with the RNA inhibitor cordycepin also did not affect adozelesin cytotoxicity. In experiments with alkylating agents, combinations of adozelesin with melphalan or cisplatin were usually additive or slightly synergistic. Adozelesin-tetraplatin combinations were synergistic at several different ratios of the two drugs, and depending on the schedule of exposure to drug. In experiments using methylxanthines, adozelesin combined synergistically with noncytotoxic doses of caffeine or pentoxifylline and resulted in several logs of increase in adozelesin cytotoxicity. In experiments with hypomethylating agents, adozelesin combined synergistically with 5-azacytidine (5-aza-CR) and 5-aza-2'-deoxycytidine (5-aza-2'-CdR). Combinations of adozelesin with tetraplatin or 5-aza-2'-CdR were also tested against B16 melanoma cells in vitro and were found to be additive and synergistic, respectively. The synergistic cytotoxicity to CHO cells of adozelesin combinations with tetraplatin, 5-aza-CR, or pentoxifylline was not due to increased adozelesin uptake or increased alkylation of DNA by adozelesin.

Assessment of toxicity, clastogenicity, mutagenicity and transforming activity of pentoxifylline in mammalian cells cultured in vitro

We tested the possible cytotoxic, clastogenic and genotoxic effects of pentoxifylline on different lines of mammalian cells cultured in vitro. This study was part of the developmental research of agapurin, since pentoxifylline represents an effective compound of this drug. Cells treated for a short time manifested a relatively high resistance to the toxic effects of pentoxifylline. Generally, only cells treated for a long time (18 h) or a short time (2 h) with high concentrations of drug manifested sensitivity to the toxic effects of pentoxifylline. Although the tested drug induced DNA synthesis inhibition in V79 and EUE cells and clastogenic effects in V79 cells, it was not able to induce either 6-TGr mutations in the HGPRT locus of V79 cells or morphological transformation of Syrian hamster embryo cells. Adding of microsomal fraction S9 to the treated cells did not markedly change the effects of pentoxifylline on different studied endpoints. We suggest that pentoxifylline has no genotoxic effects, and that the cytotoxicity and induction of chromosomal aberrations were induced by inhibition of cellular DNA replication.

Increase in tumor blood flow by pentoxifylline

PURPOSE

The effect of pentoxifylline (PTX) on the blood flow in experimental rodent tumors was investigated.

METHODS AND MATERIALS

When the R3230 AC adenocarcinoma implanted in the leg of Fischer 344 rats grew to about 1 g, the effect of PTX on the blood flow in the tumor and in the skin and muscle was determined with the microsphere method using 85Sr labelled 25 microns diameter microspheres. The SCK mammary carcinoma was induced subcutaneously in the leg or foot of A/J mice and the effect of PTX on the tumors was investigated: the blood perfusion in the leg tumors (7 mm in diameter) was determined with the 86Rb uptake method and that in the foot tumors (5 mm diameter) was determined with the laser Doppler flow (LDF) method.

RESULTS

The blood flow in the R3230 AC adenocarcinoma significantly increased when measured 30 min after an IP injection of 50 mg/kg PTX while the blood flow in the normal skin and muscle remained unchanged. The 86Rb uptake in the SCK tumor slightly increased 30 min after an IP injection of 50 mg/kg PTX. The LDF in the SCK tumors grown in the foot began to increase 5-10 min after an injection of 25 mg/kg PTX reaching 1.5-2.0 times in 20-30 min and it returned to the original level at 60 min.

CONCLUSION

The results in the present study together with our previous observation that PTX increases the tumor pO2 in rodent tumors strongly suggest that PTX may be useful for increasing the radiosensitivity of human tumors.

Hemorheologic approach in the treatment of diabetic foot ulcers

Pentoxifylline, a new trisubstituted methylxanthine derivative, is the most well known of a new group of hemorheologic agents. It has been shown to improve hemorheologic abnormalities associated with diabetes and atherosclerosis. The authors examined the role of pentoxifylline in the treatment of diabetic foot ulcers. Forty diabetic patients with foot ulcerations were included in the study, 20 of whom received conventional therapy and 20 received pentoxifylline (400 mg three times a day) in addition. Healing of ulcers after eight weeks of treatment was significantly higher in those on pentoxifylline, and the patients needed less mutilating surgery. Administration of pentoxifylline in addition to conventional therapy was significantly superior in the management of diabetic foot ulcers.

Antiplatelet effect of pentoxifylline in human whole blood

1. Pentoxifylline inhibits platelet aggregation in whole blood more than in platelet-rich plasma. 2. An inhibition of the erythrocyte uptake of adenosine contributes to the antiaggregatory effect of pentoxifylline.

Treatment of vasculogenic sexual dysfunction with pentoxifylline

OBJECTIVE

To evaluate the use of pentoxifylline to treat impotence in men with mild to moderate penile vascular insufficiency.

DESIGN

Double-blind randomized clinical trial.

SETTING

Sexual Dysfunction Clinic at VA Medical Center, Sepulveda, CA.

PARTICIPANTS

Convenience sample of couples.

INTERVENTION

Twelve weeks of treatment with placebo or 400 mg tid of pentoxifylline.

MEASUREMENTS

(1) Report of patient verified by partner as to number of coital episodes per month; (2) penile-brachial pressure index determinations.

RESULTS

Pentoxifylline therapy regularly increased the PBPI in impotent men in comparison with the placebo, frequently into the normal range. Pentoxifylline therapy was particularly useful in restoring the PBPI in men with the pelvic steal syndrome; six of seven such subjects improved into the normal range. During the pentoxifylline treatment period, in contrast with the control period, nine men were able to reestablish coital function and three had no improvement. Six couples did not attempt intercourse despite a professed interest in sexual activity; however five out of the six men experienced erections during episodes of fantasy or attempts at masturbation during treatment. There were no complications of therapy.

CONCLUSIONS

These promising preliminary results suggest a well tolerated alternative therapy for erectile dysfunction in patients with mild to moderate penile vascular disease.

Influence of pentoxifylline on renal function in HIV-seropositive patients

Pentoxifylline (PTX) has potential usefulness in HIV-seropositive patients due to its beneficial effects on renal function, its inhibitory effects on tumor necrosis factor alpha, and its vascular effects on microcirculatory disturbances. The present study prospectively evaluated the effects of multiple oral doses of PTX (400 mg three times daily for 12 weeks) on renal function in 11 HIV-seropositive patients compared with 14 control patients. Four of these patients had HIV-associated nephropathy, manifested by high urinary microalbumin outputs (72 +/- 56 micrograms/min; mean +/- SD). Ambulatory 24-h urine collections were analyzed for creatinine, electrolytes, and immunological markers at weekly intervals for 12 weeks. Urine flow rates diminished to one-half baseline values by week 12; changes were related to both time and treatment sequences. There were significant decreases in creatinine clearances and electrolyte excretion rates over the study period that were not associated with treatment regimens. No differences were found in fractional electrolyte, uric acid, microalbumin, and neopterin excretion rates either between or within groups. One subject with high microalbumin excretion rates had a significant drop over the 12 weeks (133 to 4 micrograms/min); the other 3 subjects had similar or elevated microalbumin outputs by the end of the study. Although well tolerated, therapeutic doses of PTX did not significantly affect renal function in HIV-seropositive patients.

Anti-inflammatory effects of pentoxifylline in claudication

We measured neutrophil elastase/alpha 1 proteinase inhibitor complex (E/alpha) levels by ELISA in plasma samples drawn from 19 patients with claudication, before and at 1 and 2 months after initiation of pentoxifylline (PTF), 400 mg. p.o. tid. Plasma E/alpha levels declined in all eight patients whose initial values were more than 300 ng elastase per ml. Whole blood viscosity (wbv) was reduced by two months' treatment in 12 of 14 patients tested. The relative change in wbv was significantly related to the relative change in E/alpha (R2 = 0.8), for patients with elevated initial E/alpha levels, suggesting a common or related mechanism for the two effects. Plasma crosslinked fibrin D-dimer fragments (XDP) measured by ELISA as indicators of coagulation activity were lower compared to pretreatment levels in 9 of 10 samples drawn when symptoms were improved on PTF, whereas they were increased in 6 of 9 samples drawn when symptoms were worse or unchanged. Plasma viscosity, C-reactive protein and alpha 1-acid-glycoprotein did not change significantly with PTF treatment. Together these findings are consistent with the possibility that reduced microvascular neutrophil activation and coagulation play a role in the clinical efficacy of PTF in intermittent claudication.

Benefit of vascular decongestion in glycerol-induced acute renal failure

The post insult administration of vascular decongestants has resulted in attenuation of experimental acute renal failure (ARF) following the introduction of various nephrotoxins including drugs, heavy metals, and endotoxin. In the present study, the dose-dependent effects of a novel methylxanthine, HWA-138, were studied in the glycerol-induced murine model of ARF. Renal function, assessed by serial inulin clearances at 24 and 48 h after glycerol injection, urinary electrolyte excretion rates, and renal morphology, was compared between controls and those given glycerol and single i.v. doses of 0.1, 0.5, 1.0, 5.0, and 10.0 mg/kg of HWA-138, or physiologic saline. Whereas significant renal dysfunction was found in all animal groups given glycerol, the mean inulin clearance values of animals given HWA-138 1 mg/kg closely approximated values found in control rats. There were no changes in renal electrolyte excretion rates in animals given HWA-138 compared with relative natriuresis found in untreated glycerol ARF rat. Although a modest decrease in medullary congestion was associated with rats given 1 mg/kg of HWA-138, there was no obvious structural improvement found with HWA-138. The present data provide further evidence of the potential of methylxanthines in the glycerol-ARF murine model.

Hemorheologic effects of Meclomen including effect in malignant melanoma

Sodium Meclofenamate, (Meclomen) (M) is a non-steroidal anti-inflammatory drug, which inhibits both cyclooxygenases and lipooxygenases of the arachidonic acid cascade (AA). (M) inhibited adenosine diphosphosphate (ADP) induced platelet aggregation, arachidonic acid (AA) induced platelet aggregation and collagen induced platelet aggregation. (M) inhibited platelet factor 3 availability when measured by Stypven clotting time. Red cells from patients with advanced malignancies and normal red cells stored in blood banks exhibited loss of deformability. (M) enhanced red cell deformability in these blood samples.

Pentoxifylline improves pulmonary gas exchange

Pentoxifylline is a xanthine derivative with hemorrheologic and vascular properties that may improve gas exchange in patients with chronic obstructive pulmonary disease (COPD). We tested this hypothesis in 12 patients with COPD (mean FEV1 = 40 percent predicted; mean DCO, 8.6 ml/min/mm Hg) randomly divided into a treatment and control group and six healthy volunteers. Following establishment of baseline DCO and maximum expiratory flow volume (MEFV) curve values, each subject in the treatment and healthy groups took 400 mg of pentoxifylline three times a day for 12 weeks. Weekly DCO and MEFV curves were measured before treadmill exercise in both COPD groups and before and after exercise in the healthy group. The MEFV curve parameters from the final three weeks of therapy did not differ significantly from baseline values. During this time, however, the treatment COPD group's resting DCO rose by 8.2 +/- 2.4 percent over baseline level (p less than 0.01). Treadmill walk time increased from 17.7 +/- 2.9 minutes to 23.2 +/- 2.9 minutes (p less than 0.02). This was accompanied by improved exercise oxygen saturation measured by oximetry (SoxiO2). Premedication SoxiO2 fell from 92.8 +/- 1.2 percent to 88.6 +/- 2.5 percent during exercise, and from 94.4 +/- 1.1 percent to only 91.8 +/- 1.0 percent after 12 weeks of medication (p less than 0.05). No such improvement was noted in the control COPD group. Although the healthy group's resting SoxiO2 and DCO did not change during treatment, their exercise DCO increased significantly from 36.3 +/- 3.1 ml/min/mm Hg to 41.8 +/- 3.5 ml/min/mm Hg (p less than 0.001). These data demonstrate that pentoxifylline improves gas exchange, possibly by increasing cardiac output, and/or by raising mixed venous PO2, and/or by improving blood flow to underperfused alveoli.

Effects of pentoxifylline in experimental acute renal failure

The beneficial effects of post-insult administration of pentoxifylline, a novel hemorheologic agent experimentally studied in various ischemic diseases, were evaluated in two models of acute renal failure (ARF): direct nephrotoxicity (mercuric chloride 4 mg/kg via femoral vein) and hemoglobinuria (glycerol 10 ml/kg i.m.). Glomerular filtration rate (GFR) was estimated at baseline and following drug administration by creatinine clearances; tubular function was assessed by renal fractional and absolute electrolyte excretions. The incidence of mortality was decreased with a single dose of pentoxifylline 45 mg/kg (21.4%) compared to control rats (71.4%) 48 hours following induction of ARF with mercuric chloride. Although GFR and renal electrolyte excretion were significantly greater in rats given pentoxifylline compared to saline, the magnitude of difference was minimal. A return to baseline GFR was observed in the glycerol group administered a single i.p. dose of pentoxifylline 45 mg/kg (100.8 +/- 54.8%) compared to saline controls (45.6 +/- 22.7%; P less than 0.05). No differences in renal electrolyte excretion or mortality were observed in this model. Taken together, these data suggest that pentoxifylline, administered shortly after the initiation of ARF, exerts an ameliorative effect on the course and mortality of experimental ARF. The mechanism of amelioration most likely involves the stimulation of renal vasodilator prostaglandins as well as prevention of vascular congestion.

Prevention of cyclosporine-induced nephrotoxicity with pentoxifylline

Although cyclosporine (CSA) is established in the prevention of allograft rejection, its use has been associated with dose-limiting toxicities, most notably to the kidney and liver. To date, the pathogenesis of the acute form of nephrotoxicity is unclear but may be related to inhibition of vasodilatory prostaglandins resulting in vasoconstriction and ischemia. The present study investigated the coadministration of CSA with a unique hemorheologic agent, pentoxifylline (PTX), in the murine model. A total of 48 rats were orally dosed with CSA 25 mg/kg for 10 days with either PTX 45 mg/kg i.p. or saline every 12 hr. Posttreatment renal function, assessed by creatinine (CCR) and inulin (CIN) clearances and renal electrolyte handling, was compared with baseline data and between groups. In an attempt to assess prostaglandin-mediated changes in enteral absorption, oral CSA pharmacokinetics with and without PTX were compared to the pharmacokinetics of similar groups (N = 8) administered i.v. CSA. Mean CIN of rats coadministered CSA and PTX (942 +/- 214 microliters/min/g KW) was similar to control rats 884 +/- 185 microliters/min/g KW); both were significantly greater than CSA alone (537 +/- 211 microliters/min/g KW; p less than .01). Likewise, percent of baseline CCR was significantly reduced in rats treated CSA (61 +/- 24%) compared to controls 113 +/- 41%) and rats coadministered PTX (117 +/- 75%; p less than .05). No differences in percent change from baseline electrolyte handling were observed among groups. Further, no differences in CSA pharmacokinetics with or without PTX were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin depolymerization and inhibition of capping induced by pentoxifylline in human lymphocytes and neutrophils

Pentoxifylline is used clinically for the treatment of intermittent claudication. It is believed to exert its effect by altering the rheologic properties of blood. The cytoskeleton plays an important role in the maintenance of cell structure and function. In particular, alterations in the state of actin seem to play an important role in cell motility. Therefore, we examined the effect of pentoxifylline on the actin state in human polymorphonuclear leukocytes (PMN) and mononuclear cells. Pentoxifylline (10 mM final concentration) decreased F-actin content in both PMN and mononuclear cells. Pentoxifylline also inhibited concanavalin A-induced capping in PMN and mononuclear cells. Similarly, surface immunoglobulin capping in B lymphocytes was also inhibited. Pretreatment of cells with pertussis toxin did not inhibit pentoxifylline-induced decrease in F-actin, suggesting pentoxifylline does not act through pertussis toxin-sensitive G-proteins. Dibutyryl cyclic AMP failed to show any significant effect on the F-actin content in PMN. Therefore, the effect of pentoxifylline cannot be attributed to changes in cyclic AMP levels. Chemotactic peptide-induced actin polymerization was unaffected in PMN when expressed as percent changes in F-actin. The observations reported here suggest that the rheological effects of pentoxifylline might be due to its effects on the actin state in the cellular elements of the blood. Further studies on the mechanism of action of pentoxifylline on actin state in leukocytes will prove useful in delineating the physiological mechanisms regulating actin state in leukocytes.