Oral pentamidine-loaded poly(d,l-lactic-co-glycolic) acid nanoparticles: an alternative approach for leishmaniasis treatment.

Leishmaniasis is a group of diseases caused by a protozoa parasite from one of over 20 Leishmania species. Depending on the tissues infected, these diseases are classified as cutaneous, mucocutaneous and visceral leishmaniasis. For the treatment of leishmaniasis refractory to antimony-based drugs, pentamidine (PTM) is a molecule of great interest. However, PTM displays poor bioavailability through oral routes due to its two strongly basic amidine moieties, which restricts its administration by a parenteral route and limits its clinical use. Among various approaches, nanotechnology-based drug delivery systems (nano-DDS) have potential to overcome the challenges associated with PTM oral administration. Here, we present the development of PTM-loaded PLGA nanoparticles (NPs) with a focus on the characterization of their physicochemical properties and potential application as an oral treatment of leishmaniasis. NPs were prepared by a double emulsion methodology. The physicochemical properties were characterized through the mean particle size, polydispersity index (PdI), zeta potential, entrapment efficiency, yield process, drug loading, morphology, in vitro drug release and in vivo pharmacological activity. The PTM-loaded PLGA NPs presented with a size of 263 ± 5 nm (PdI = 0.17 ± 0.02), an almost neutral charge (-3.2 ± 0.8 mV) and an efficiency for PTM entrapment of 91.5%. The release profile, based on PTM dissolution, could be best described by a zero-order model, followed by a drug diffusion profile that fit to the Higuchi model. In addition, in vivo assay showed the efficacy of orally given PTM-loaded PLGA NPs (0.4 mg kg-1) in infected BALB/c mice, with significant reduction of organ weight and parasite load in spleen (p-value < 0.05). This work successfully reported the oral use of PTM-loaded NPs, with a high potential for the treatment of visceral leishmaniasis, opening a new perspective to utilization of this drug in clinical practice.

Specific Cell Targeting Therapy Bypasses Drug Resistance Mechanisms in African Trypanosomiasis.

African trypanosomiasis is a deadly neglected disease caused by the extracellular parasite Trypanosoma brucei. Current therapies are characterized by high drug toxicity and increasing drug resistance mainly associated with loss-of-function mutations in the transporters involved in drug import. The introduction of new antiparasitic drugs into therapeutic use is a slow and expensive process. In contrast, specific targeting of existing drugs could represent a more rapid and cost-effective approach for neglected disease treatment, impacting through reduced systemic toxicity and circumventing resistance acquired through impaired compound uptake. We have generated nanoparticles of chitosan loaded with the trypanocidal drug pentamidine and coated by a single domain nanobody that specifically targets the surface of African trypanosomes. Once loaded into this nanocarrier, pentamidine enters trypanosomes through endocytosis instead of via classical cell surface transporters. The curative dose of pentamidine-loaded nanobody-chitosan nanoparticles was 100-fold lower than pentamidine alone in a murine model of acute African trypanosomiasis. Crucially, this new formulation displayed undiminished in vitro and in vivo activity against a trypanosome cell line resistant to pentamidine as a result of mutations in the surface transporter aquaglyceroporin 2. We conclude that this new drug delivery system increases drug efficacy and has the ability to overcome resistance to some anti-protozoal drugs.

In vitro and in vivo evaluation of 28DAP010, a novel diamidine for treatment of second-stage African sleeping sickness.

African sleeping sickness is a neglected tropical disease transmitted by tsetse flies. New and better drugs are still needed especially for its second stage, which is fatal if untreated. 28DAP010, a dipyridylbenzene analogue of DB829, is the second simple diamidine found to cure mice with central nervous system infections by a parenteral route of administration. 28DAP010 showed efficacy similar to that of DB829 in dose-response studies in mouse models of first- and second-stage African sleeping sickness. The in vitro time to kill, determined by microcalorimetry, and the parasite clearance time in mice were shorter for 28DAP010 than for DB829. No cross-resistance was observed between 28DAP010 and pentamidine on the tested Trypanosoma brucei gambiense isolates from melarsoprol-refractory patients. 28DAP010 is the second promising preclinical candidate among the diamidines for the treatment of second-stage African sleeping sickness.

Pharmacokinetic comparison to determine the mechanisms underlying the differential efficacies of cationic diamidines against first- and second-stage human African trypanosomiasis.

Human African trypanosomiasis (HAT), a neglected tropical disease, is fatal without treatment. Pentamidine, a cationic diamidine, has been used to treat first-stage (hemolymphatic) HAT since the 1940s, but it is ineffective against second-stage (meningoencephalitic, or central nervous system [CNS]) infection. Novel diamidines (DB75, DB820, and DB829) have shown promising efficacy in both mouse and monkey models of first-stage HAT. However, only DB829 cured animals with second-stage infection. In this study, we aimed to determine the mechanisms underlying the differential efficacies of these diamidines against HAT by conducting a comprehensive pharmacokinetic characterization. This included the determination of metabolic stability in liver microsomes, permeability across MDCK and MDR1-MDCK cell monolayers, interaction with the efflux transporter MDR1 (P-glycoprotein 1 or P-gp), drug binding in plasma and brain, and plasma and brain concentration-time profiles after a single dose in mice. The results showed that DB829, an azadiamidine, had the highest systemic exposure and brain-to-plasma ratio, whereas pentamidine and DB75 had the lowest. None of these diamidines was a P-gp substrate, and the binding of each to plasma proteins and brain differed greatly. The brain-to-plasma ratio best predicted the relative efficacies of these diamidines in mice with second-stage infection. In conclusion, pharmacokinetics and CNS penetration influenced the in vivo efficacies of cationic diamidines against first- and second-stage HAT and should be considered when developing CNS-active antitrypanosomal diamidines.

Systematic exploration of synergistic drug pairs.

Drug synergy allows a therapeutic effect to be achieved with lower doses of component drugs. Drug synergy can result when drugs target the products of genes that act in parallel pathways ('specific synergy'). Such cases of drug synergy should tend to correspond to synergistic genetic interaction between the corresponding target genes. Alternatively, 'promiscuous synergy' can arise when one drug non-specifically increases the effects of many other drugs, for example, by increased bioavailability. To assess the relative abundance of these drug synergy types, we examined 200 pairs of antifungal drugs in S. cerevisiae. We found 38 antifungal synergies, 37 of which were novel. While 14 cases of drug synergy corresponded to genetic interaction, 92% of the synergies we discovered involved only six frequently synergistic drugs. Although promiscuity of four drugs can be explained under the bioavailability model, the promiscuity of Tacrolimus and Pentamidine was completely unexpected. While many drug synergies correspond to genetic interactions, the majority of drug synergies appear to result from non-specific promiscuous synergy.

Synthesis and biological evaluation of L-valine-amidoximeesters as double prodrugs of amidines.

In general, drugs containing amidines suffer from poor oral bioavailability and are often converted into amidoxime prodrugs to overcome low uptake from the gastrointestinal tract. The esterification of amidoximes with amino acids represents a newly developed double prodrug principle creating derivatives of amidines with both improved oral availability and water solubility. N-valoxybenzamidine (1) is a model compound for this principle, which has been transferred to the antiprotozoic drug pentamidine (8). Prodrug activation depends on esterases and mARC and is thus independent from activation by P450 enzymes. Therefore, drug-drug interactions or side effects will be minimized. The synthesis of these two compounds was established, and their biotransformation was studied in vitro and in vivo. Bioactivation of N-valoxybenzamidine (1) and N,N'-bis(valoxy)pentamidine (7) via hydrolysis and reduction has been demonstrated in vitro with porcine and human subcellular enzyme preparations and the mitochondrial Amidoxime Reducing Component (mARC). Moreover, activation of N-valoxybenzamidine (1) by porcine hepatocytes was studied. In vivo, the bioavailability in rats after oral application of N-valoxybenzamidine (1) was about 88%. Similarly, N,N'-bis(valoxy)pentamidine (7) showed oral bioavailability. Analysis of tissue samples revealed high concentrations of pentamidine (8) in liver and kidney.

Drug reformulation for a neglected disease. The NANOHAT project to develop a safer more effective sleeping sickness drug.

BACKGROUND: Human African trypanosomiasis (HAT or sleeping sickness) is caused by the parasite Trypanosoma brucei sspp. The disease has two stages, a haemolymphatic stage after the bite of an infected tsetse fly, followed by a central nervous system stage where the parasite penetrates the brain, causing death if untreated. Treatment is stage-specific, due to the blood-brain barrier, with less toxic drugs such as pentamidine used to treat stage 1. The objective of our research programme was to develop an intravenous formulation of pentamidine which increases CNS exposure by some 10-100 fold, leading to efficacy against a model of stage 2 HAT. This target candidate profile is in line with drugs for neglected diseases inititative recommendations. METHODOLOGY: To do this, we evaluated the physicochemical and structural characteristics of formulations of pentamidine with Pluronic micelles (triblock-copolymers of polyethylene-oxide and polypropylene oxide), selected candidates for efficacy and toxicity evaluation in vitro, quantified pentamidine CNS delivery of a sub-set of formulations in vitro and in vivo, and progressed one pentamidine-Pluronic formulation for further evaluation using an in vivo single dose brain penetration study. PRINCIPAL FINDINGS: Screening pentamidine against 40 CNS targets did not reveal any major neurotoxicity concerns, however, pentamidine had a high affinity for the imidazoline2 receptor. The reduction in insulin secretion in MIN6 ß-cells by pentamidine may be secondary to pentamidine-mediated activation of ß-cell imidazoline receptors and impairment of cell viability. Pluronic F68 (0.01%w/v)-pentamidine formulation had a similar inhibitory effect on insulin secretion as pentamidine alone and an additive trypanocidal effect in vitro. However, all Pluronics tested (P85, P105 and F68) did not significantly enhance brain exposure of pentamidine. SIGNIFICANCE: These results are relevant to further developing block-copolymers as nanocarriers, improving BBB drug penetration and understanding the side effects of pentamidine.

inPentasomes: An innovative nose-to-brain pentamidine delivery blunts MPTP parkinsonism in mice.

Preclinical and clinical evidences have demonstrated that astroglial-derived S100B protein is a key element in neuroinflammation underlying the pathogenesis of Parkinson's disease (PD), so much as that S100B inhibitors have been proposed as promising candidates for PD targeted therapy. Pentamidine, an old-developed antiprotozoal drug, currently used for pneumocystis carinii is one of the most potent inhibitors of S100B activity, but despite this effect, is limited by its low capability to cross blood brain barrier (BBB). To overcome this problem, we developed a non-invasive intranasal delivery system, chitosan coated niosomes with entrapped pentamidine (inPentasomes), in the attempt to provide a novel pharmacological approach to ameliorate parkinsonism induced by subchronic MPTP administration in C57BL-6 J mice. inPentasomes, prepared by evaporation method was administered daily by intranasal route in subchronic MPTP-intoxicated rodents and resulted in a dose-dependent manner (0.001-0.004 mg/kg) capable for a significant Tyrosine Hydroxylase (TH) positive neuronal density rescue in both striatum and substantia nigra of parkinsonian mice. In parallel, inPentasomes significantly decreased the extent of glial-related neuroinflammation through the reduction of specific gliotic markers (Iba-1, GFAP, COX-2, iNOS) with consequent PGE2 and NO2- release reduction, in nigrostriatal system. inPentasomes-mediated S100B inhibition resulted in a RAGE/NF-κB pathway downstream inhibition in the nigrostriatal circuit, causing a marked amelioration of motor performances in intoxicated mice. On the basis of our results, chitosan coated niosomes loaded with pentamidine, the inPentasome system, self-candidates as a promising new intranasal approach to mitigate parkinsonism in humans and possibly paves the way for a possible clinical repositioning of pentamidine as anti-PD drug.

Development of a liposome formulation for improved biodistribution and tumor accumulation of pentamidine for oncology applications.

Pentamidine isethionate, widely used for the treatment of parasitic infections, has shown strong anticancer activity in cancer cells and models of melanoma and lung cancer. Systemic administration of pentamidine is associated with serious toxicities, particularly renal, affecting as many as 95% of patients (O'Brien et al., 1997). This work presents the development of a liposome pentamidine formulation for greater tumor accumulation and lower drug exposure to vulnerable tissues. Liposomes formulated with saturated/unsaturated phospholipids of different chain lengths, varying cholesterol content, and surface PEG were explored to understand the effects of such variations on drug release, encapsulation efficiency, stability and in vivo performance. Saturated phospholipids with longer chain lengths, higher cholesterol content and PEG resulted in greater stability. The optimal formulation obtained showed significantly lower clearance rate (3.6 ± 1.2 mL/h/Kg) and higher AUC0-inf (348 ± 31 µmol/L × h) in vivo when compared to free drug (414 ± 138 mL/h/Kg and 2.58 ± 0.74 µmol/L × h, respectively). In tumor-bearing mice, liposomal delivery decreased kidney drug levels by up to 5-fold at 6 and 24h post-administration. Tumor drug exposure was up to 12.7-fold greater with liposomal administration compared to free drug. Overall, the liposomal pentamidine formulation developed has significant potential for the treatment of solid tumors.

Transporters in African trypanosomes: role in drug action and resistance.

Sleeping sickness is an increasing problem in many parts of sub-Saharan Africa. The problems are compounded by the lack of new medication, and the increasing resistance against traditional drugs such as melarsoprol, berenil and isometamidium. Over the last few years, much progress has been made in understanding how drug action, and the development of resistance, is related to the mechanisms by which the parasite ingests the drugs. In some cases novel transporters have been identified. In other cases, transporters do not appear to be involved in drug uptake, and selectivity must lie with other parasite features, such as a specific target or activation of the drug. Lessons learned from studying the uptake of drugs currently in use may assist the design of a much needed new generation of trypanocides.

Deposition of aerosolized pentamidine and failure of pneumocystis prophylaxis.

OBJECTIVE: To determine if outcome of Pneumocystis carinii prophylaxis is related to total lung dose of aerosolized pentamidine. SETTING: AIDS treatment centers at a VA and University Hospital. PATIENTS: Fifty-eight HIV-infected patients receiving P carinii prophylaxis with aerosolized pentamidine using a nebulizer (CIS-US AeroTech II) were followed up over a 90-week period. Treatment consisted of 60 to 90 mg every two weeks. MEASUREMENTS: In all patients, deposition of pentamidine aerosol was measured using a radioaerosol filter technique. Factors thought to be important in deposition, nebulizer output and breathing pattern were also measured. Six months later, repeated deposition studies were performed in 20 patients. Pentamidine dose to the lung was related to occurrence of P carinii pneumonia and correlated with nebulizer function and breathing parameters. Outcome was assessed in terms of pentamidine deposition and patient characteristics, including demographic, immunologic, physiologic, and medical variables. RESULTS: Ten patients (17.2 percent) had development of P carinii pneumonia. However, pentamidine deposited in the failures (8.18 +/- 4.74 mg) was no different than deposition in protected patients (6.39 +/- 3.07 mg, p = NS). Most of the variability in deposition was accounted for by variability in nebulizer output (r = 0.919, p less than 0.001). Deposition did not significantly correlate with any of the measured breathing parameters. Serial deposition measurements were not significantly different by paired analysis. The incidence of P carinii pneumonia did not correlate with any measured patient characteristic. CONCLUSIONS: Failure of aerosolized pentamidine prophylaxis is not related to total lung dose of pentamidine. Other factors such as inadequate microscopic deposition between alveoli, pentamidine clearance, or drug resistance may be important. In HIV-infected patients, interpatient variability in aerosol deposition can be reduced by reducing variability in nebulizer output rather than control of breathing pattern.

Estimation of fetal risk from aerosolized pentamidine in pregnant healthcare workers.

Inhaled pentamidine is used to treat Pneumocystis carinii pneumonia. Its potential effects on DNA have raised concerns about its safety for pregnant healthcare workers. We used a pharmacokinetic approach to estimate the fetal risks, based on the published data of pentamidine renal clearance and of urinary pentamidine concentrations in healthcare workers exposed to aerosolized pentamidine. The maximum pentamidine doses (intravenous equivalent) that healthcare workers were exposed to were calculated to be 9.8 micrograms/kg/d and 1.7 microgram/kg/d at the two different institutions reported. In parallel, based on animal data, we derived the intravenous-equivalent reference doses for embryolethality and for teratogenicity, the doses that can be viewed as tentative safe exposure levels. These analyses reveal that the exposure levels of a healthcare worker to aerosolized pentamidine are estimated to be in the vicinity of the teratogenic reference dose (4 micrograms/kg/d) and greater than the embryolethal reference dose (0.08 microgram/kg/d). Further improvement of the pentamidine administration technique and of environmental management in hospitals is warranted.

A randomized comparison of once-monthly or twice-monthly high-dose aerosolized pentamidine prophylaxis.

RESULTS: Ten of the 146 (7 percent) evaluable subjects developed PCP during the year study period, and there was no difference in the efficacy of the two regimens. Among patients receiving secondary prophylaxis, the attack rate of PCP at 1 year was 11 percent. This compares favorably with a 1-year attack rate of 19 percent in similar patients receiving standard dose (300 mg) prophylaxis and suggests, but does not prove, a dose-response effect. Concentrations of pentamidine in BAL fluid were not significantly different among the three lobes of the lung. Intrapulmonary pentamidine did not accumulate during the year of study. Aerosolized pentamidine was associated with a marginal but statistically significant increase in the residual volume, decreased flow rates, and increased airway reactivity. OBJECTIVE: The optimal regimen of aerosolized pentamidine in unknown. Published data suggest that there is a dose-response effect and that the occurrence of Pneumocystis carinii pneumonia (PCP) has been associated with prolongation of the interval between doses. The purpose of this study was to compare the efficacy, pharmacokinetics, and physiologic effects of two high-dose regimens of aerosolized pentamidine prophylaxis. DESIGN: Prospective, randomized study of 300 mg twice monthly vs 600 mg once monthly during a 1-year observation period. Pentamidine concentrations in plasma and bronchoalveolar lavage (BAL) fluid were measured and serial pulmonary function was measured. SETTING: A large teaching hospital in San Francisco. PATIENTS: One hundred fifty-one adult (age > 18 years) men with human immunodeficiency virus infection. Of 146 evaluable patients, prophylaxis was primary (no prior PCP) in 108 (75 percent) and secondary (one prior episode of PCP) in 38 (25 percent). MEASUREMENTS: Date and diagnosis of PCP, occurrence of drug toxicity, pulmonary function testing, and concentrations of pentamidine in BAL and plasma. CONCLUSIONS: The data suggest, but do not prove, that a dose-response effect has been demonstrated, and that high-dose aerosolized pentamidine may further reduce the attack rate of PCP. These preliminary observations should be confirmed in a double-blind trial comparing 300 mg with 600 mg administered once monthly. The clinical relevance of the adverse pulmonary effects is unclear and requires further investigation.

Delivered dose and regional distribution of aerosolized pentamidine using different delivery systems.

Aerosolized pentamidine has gained acceptance as a form of treatment for the prevention of Pneumocystis carinii pneumonia. However, different studies have used different delivery systems, making comparison of results difficult. This study was designed to determine the dose to the lung, regional distribution, extrapulmonary deposition, and side effects using four different delivery systems: the Respirgard II, the Aero Tech II, the Portasonic, and the Fisoneb. Ten homosexual subjects who were infected with HIV virus were studied. Particle size, as determined by cascade impaction, varied among nebulizers. Mass median aerodynamic diameter was 0.90 mu for the Respirgard II, 1.30 mu for the Aero Tech II, 1.40 mu for the Portasonic, and 3.90 mu for the Fisoneb. Subjects inhaled a solution containing 60 mg pentamidine in 3 ml of sterile water, and 1 ml of 99mTc bound to human serum albumin for each nebulizer system. Regional distribution was determined by comparing each deposition scan obtained by a posteriorly positioned gamma camera to the subjects' equilibrium xeon scan. The deposition scan was used to quantitate lung dose and extrapulmonary deposition. Marked differences were seen among delivery systems. Dose to the lung varied fivefold. The deposition in the lung, expressed as a percentage of the amount placed in the nebulizer, was 5.3 percent in the Respirgard II, 15.7 percent in the Aero Tech II, 17.30 percent in the Portasonic, and 26.4 percent in the Fisoneb (p less than 0.0001 by ANOVA). Wide differences in extrapulmonary deposition and side effects were noted among nebulizers (Fisoneb greater than Portasonic, Aero Tech II greater than Respirgard II). Regional distribution in the lung as measured by the AI, also showed differences, with the Respirgard having the most homogeneous distribution of aerosol (Respirgard greater than Portasonic, Aero Tech greater than Fisoneb). Regional distribution and extrapulmonary deposition varied in a manner consistent with the particle size of the nebulizers. These data should provide a framework for the comparison and design of future clinical studies using these delivery systems.

Regional deposition and regional ventilation during inhalation of pentamidine.

In most patients, the deposition of aerosolized pentamidine (AP) is less in the apex of the lung relative to the base. As the apex of the lung is relatively less ventilated than the base, it is possible that reduced regional ventilation may explain the inhomogeneity in regional drug deposition. The purpose of this study was to measure the relationship between regional deposition of AP and regional ventilation, and the influence of particle size and airway caliber on this relationship. Ten subjects with HIV infection who were receiving prophylaxis with AP were recruited. Using krypton (81mKr), we measured regional ventilation during treatment with AP, labeled with 99mTc. Two nebulizers were used (Respirgard II and Fisoneb) that produced particles of different size. In addition, patients were studied with and without a bronchodilator because changes in airway geometry can affect sites of particle deposition. There was no significant correlation between regional ventilation and regional particle deposition (r = 0.00, linear regression). Particle deposition in the upper lobes relative to the lower lobes was less than would be predicted by regional ventilation, by a ratio of 0.84 +/- 0.03 (mean +/- SE). Using two-way analysis of variance (ANOVA), the upper to lower zone deposition pattern was not affected by either nebulizer or by the use of albuterol. The Fisoneb had significantly more central deposition relative to the jet nebulizer (mean +/- SE, skC/P: Fisoneb 1.3 +/- 0.1, Respirgard 1.1 +/- 0.1, p = 0.005, two-way ANOVA). The use of a bronchodilator did not significantly affect the central/peripheral deposition pattern. We conclude that differences in deposition between upper and lower lung regions are not accounted for simply by differences in regional ventilation in patients undergoing prophylaxis with AP. In assessing the cause of regional inhomogeneities of pharmaceutical aerosol deposition (and in devising strategies to achieve more uniform distribution), regional ventilation should be measured directly rather than be inferred from the deposition pattern of the aerosol.

Controlled dissolution from wax-coated aerosol particles in canine lungs.

Treatment of pulmonary and systemic diseases may be improved and toxicity reduced by pulmonary deposition of drug-containing aerosols exhibiting delayed dissolution. Aqueous disodium fluorescein and pentamidine aerosols were dried, concentrated, and condensation coated with paraffin wax. The apparent mass median aerodynamic diameters of the coated fluorescein particles were 2.8-4.0 microns. Wax-to-fluorescein ratios were 0.38-1.05. The dissolution half times determined using a single-pass flow system were 1.5 min for uncoated fluorescein and 0.8 min for uncoated pentamidine. These increased over threefold when the aerosols were coated with paraffin wax to maxima of 5.3 and 2.6 min, respectively. Wax-coated aerosols generated from fluorescein mixed with 99mTc-labeled iron oxide colloid delivered to the canine lungs demonstrated a 3.4-fold increase in the absorption half time of disodium fluorescein compared with uncoated fluorescein (11.2 vs. 38.4 min). The absence of changes in pulmonary function on inhalation of these wax-coated aerosols, together with a high drug load and delayed release, establishes a foundation for future therapeutic applications.

Intrapulmonary and systemic pharmacokinetics of aerosolized pentamidine used for prophylaxis of pneumocystis carinii pneumonia in patients infected with the human immunodeficiency virus.

A study was conducted to determine the intrapulmonary and systemic pharmacokinetics of aerosolized pentamidine prophylaxis (APP) in patients infected with human immunodeficiency virus (HIV). 151 patients received high-dose (300 mg twice a month or 600 mg once a month) APP as part of a previously published clinical trial, and 29 additional patients received standard-dose (300 mg once a month) APP. Serial blood samples were obtained from the first cohort: 577 samples were obtained from 76 patients in the group given 600 mg once a month, and 554 blood samples were obtained from 75 patients in the group given 300 mg twice a month. In 9 of the 151 patients, bronchoscopy and tri-lobar (right upper, middle, and lower lobe) bronchoalveolar lavage (BAL) were performed 6 and 12 months after initiation of APP. Unilobar (right middle lobe) BAL was performed in the 29 patients infected with HIV who underwent bronchoscopy for diagnostic purposes. Pentamidine was measured using a chromatographic (HPLC) assay. The concentrations (mean +/- SD) of pentamidine in plasma in the groups given 300 mg twice a month and 600 mg once a month were 5.3 +/- 6.1 ng/mL and 8.8 +/- 9.6 ng/mL, respectively, and accumulation did not occur. The BAL supernatant and alveolar cell pentamidine concentrations were not significantly different in the 3 lobes and ranged from 16.5 +/- 7.7 ng/mL to 29.2 +/- 19.5 ng/mL and 1255 +/- 1142 ng/mg protein to 1572 +/- 1161 ng/mg protein in the group given 300 mg twice a month; and from 5.5 +/- 2.9 ng/mL to 9.4 +/- 7.7 ng/mL and 339 +/- 201 ng/mg protein to 571+/- 681 ng/mg protein in the group given 600 mg once a month. The intropulmonary concentrations of pentamidine at 6 and 12 months were not significantly different. In 18 of the 29 patients who received 1 to 7 prior monthly doses of standard APP, drug concentrations in BAL increased linearly (y = 2.05x) with the number of doses administered before bronchoscopy. These data indicate that intrapulmonary drug concentrations continue to increase for approximately 6 months after the initiation of APP, at which time steady state is achieved, and that administration of high dose APP is probably safe.

Pentamidine, an inhibitor of spinal flexor reflexes in rats, is a potent N-methyl-D-aspartate (NMDA) antagonist in vivo.

The present study examined whether the antimicrobial agent pentamidine exerts an antagonistic action at the N-methyl-D-aspartate (NMDA) receptor as tested on spinal reflexes in rats in vivo. After intrathecal injection both the specific NMDA antagonist (-)-2-amino-7-phosphonoheptanoate and pentamidine dose-dependently reduced the magnitude of the polysynaptic flexor reflex without affecting the monosynaptic H-reflex. In contrast, the non-NMDA antagonist 6,7-dinitroquinoxaline-2,3-dione depressed the H-reflex in a dose-dependent manner without affecting the flexor reflex. The depressant effect of pentamidine on the flexor reflex was prevented by coadministration with NMDA but not with the non-NMDA agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. These data suggest that pentamidine exerts an antagonistic action at the NMDA receptor in vivo.

Pentamidine concentrations in plasma, whole blood and cerebrospinal fluid during treatment of Trypanosoma gambiense infection in Côte d'Ivoire.

Pentamidine concentrations in plasma, whole blood and cerebrospinal fluid (CSF) were determined in 11 patients with Trypanosoma gambiense infection without involvement of the central nervous system in Côte d'Ivoire. Blood samples were drawn during a 48 h period after the first and last dose of pentamidine dimesylate given as 10 intramuscular injections on alternate days. Maximum plasma concentrations were generally attained within one hour after injection but varied extensively (420-13420 nmol/litre). The median plasma concentration 48 h after the last dose was approximately 5 times higher than that after the first dose. The ratio between whole blood and plasma concentration was approximately 2. Small amounts of the drug were found in the CSF after the last dose. The findings showed inter-individual differences in the pharmacokinetics of pentamidine. The currently recommended daily dose regimen could be questioned, as drug accumulation was pronounced. All patients were cured and the concentrations attained should be considered as parasiticidal. Further studies on the kinetics and distribution after single and multiple doses of pentamidine as well as studies on the possible relationship between adverse effects and plasma concentrations are, however, needed.

Disposition of intravenous 123iodopentamidine in man.

This study compared the disposition of the radiopharmaceutical [123I]iodopentamidine with that of pentamidine after intravenous infusion by measuring plasma concentrations of each using scintilation counting and high-performance liquid chromatography (HPLC), respectively. There was rapid hepatic uptake and biliary excretion of the 123I label. Distribution kinetics of the 123I label were similar to those of pentamidine, but its elimination half-life (41 +/- 27 h) was longer than that of pentamidine measured by HPLC (11 +/- 8 h). [123I]iodopentamidine distribution reflects that of pentamidine, but elimination of the radiopharmaceutical appears slower.