Safety, toxicokinetics and tissue distribution of long-term intravenous liposomal amphotericin B (AmBisome): a 91-day study in rats.

PURPOSE: Amphotericin B in small, unilamellar liposomes (AmBisome) is safer and produces higher plasma concentrations than other formulations. Because liposomes may increase and prolong tissue exposures, the potential for drug accumulation or delayed toxicity after chronic AmBisome was investigated. METHODS: Rats (174/sex) received intravenous AmBisome (1, 4, or 12 mg/kg), dextrose, or empty liposomes for 91 days with a 30-day recovery. Safety (including clinical and microscopic pathology) and toxicokinetics in plasma and tissues were evaluated. RESULTS: Chemical and histopathologic changes demonstrated that the kidneys and liver were the target organs for chronic AmBisome toxicity. Nephrotoxicity was moderate (urean nitrogen [BUN] < or = 51 mg/dl; creatinine unchanged). Liposome-related changes (vacuolated macrophages and hypercholesterolemia) were also observed. Although plasma and tissue accumulation was nonlinear and progressive (clearance and volume decreased, half-life increased with dose and time), most toxic changes occurred early, stabilized by the end of dosing, and reversed during recovery. There were no delayed toxicities. Concentrations in liver and spleen greatly exceeded those in plasma: kidney and lung concentrations were similar to those in plasma. Elimination half-lives were 1-4 weeks in all tissues. CONCLUSIONS: Despite nonlinear accumulation, AmBisome revealed predictable hepatic and renal toxicities after 91 days, with no new or delayed effects after prolonged treatment at high doses that resulted in plasma levels >200 microg/ml and tissue levels >3000 microg/g.

Safety and toxicokinetics of intravenous liposomal amphotericin B (AmBisome) in beagle dogs.

PURPOSE: Amphotericin B (AmB) in small, unilamellar liposomes (AmBisome) has an improved therapeutic index, and altered pharmacokinetics. The repeat-dose safety and toxicokinetic profiles of AmBisome were studied at clinically relevant doses. METHODS: Beagle dogs (5/sex/group) received intravenous AmBisome (0.25, 1, 4, 8, and 16 mg/kg/day), empty liposomes or vehicle for 30 days. AmB was determined in plasma on days 1, 14, and 30, and in tissues on day 31. Safety parameters included body weight, clinical chemistry, hematology and microscopic pathology. RESULTS: Seventeen of twenty animals receiving 8 and 16 mg/kg were sacrificed early due to weight loss caused by reduced food intake. Dose-dependent renal tubular nephrosis, and other effects characteristic of conventional AmB occurred at 1 mg/kg/day or higher. Although empty liposomes and AmBisome increased plasma cholesterol, no toxicities unique to AmBisome were revealed. Plasma ultrafiltrates contained no AmB. AmBisome achieved plasma levels 100-fold higher than other AmB formulations. AmBisome kinetics were non-linear, with clearance and distribution volumes decreasing with increasing dose. This, and nonlinear tissue uptake, suggest AmBisome disposition was saturable. CONCLUSIONS: AmBisome has the same toxic effects as conventional AmB, but they appear at much higher plasma exposures. AmBisome's non-linear pharmacokinetics are not associated with increased risk, as toxicity increases linearly with dosage. Dogs tolerated AmBisome with minimal to moderate changes in renal function at doses (4 mg/kg/day) producing peak plasma concentrations of 18-94 microg/mL.

Toxicological profile and pharmacokinetics of a unilamellar liposomal vesicle formulation of amphotericin B in rats.

AmBisome (ABLP) is a unilamellar liposomal preparation of amphotericin B that has demonstrated an improved safety profile compared to conventional amphotericin B. Single- and multiple-dose pharmacokinetics were determined by using noncompartmental methods for rats administered ABLP at 1, 3, 9, and 20 mg/kg/day. The toxicological profile was evaluated following 30 consecutive days of intravenous ABLP administration. Mean plasma amphotericin B concentrations reached 500 and 380 microg/ml (males and females, respectively) following 30 days of ABLP administration at 20 mg/kg. The overall apparent half-life was 11.2+/-4.5 h (males) or 8.7+/-2.2 h (females), and the overall clearance (CL) was 9.4+/-5.5 ml/h/kg (males) or 10.2+/-4.1 ml/h/kg (females). ABLP appears to undergo saturable disposition, resulting in a non-dose-proportional amphotericin B area under the curve and a lower CL at higher doses. Histopathological examination revealed dose-related transitional-cell hyperplasia in the transitional epithelium of the urinary tract (kidney, ureters, and urinary bladder) and moderate hepatocellular necrosis at the 20 mg/kg/day dose. Administration of ABLP in doses of up to 20 mg/kg/day resulted in 100-fold higher plasma amphotericin B concentrations, with significantly lower toxicity than that reported with conventional amphotericin B therapy.

Retinoblastoma, melanoma and the atypical mole syndrome.

Retinoblastoma patients and their relatives appear to have an increased risk of other cancers, especially melanoma, which represents 7% of second primaries in retinoblastoma survivors. Individuals belonging to families with the atypical mole syndrome (another family cancer syndrome with a genetic susceptibility to melanoma) have a recognizable phenotype, with many atypical melanocytic naevi. We report two families in which both retinoblastoma and melanoma occurred. It is of interest that in these families atypical melanocytic naevi were also demonstrated.

Pharmacology and toxicology of chronically infused epidural clonidine.HCl in dogs.

To evaluate the physiological effects and toxicity of epidural clonidine.HCl, male Beagle dogs were prepared with chronic lumbar epidural catheters and administered constant infusions of either saline (N = 10), or 80 micrograms/hr (N = 6), 200 micrograms/hr (N = 6), or 320 micrograms/hr (N = 12) clonidine.HCl at a rate of 4 ml/24 hr for 28 days. Saline infusion had no effect upon any behavioral measure. Epidural clonidine produced a dose-dependent increase in thermal skin-twitch response latency (antinociception), lowering of respiration rate, heart rate, and blood pressure, and increased sedation. The effects were maximum from approximately Day 1 to Day 3 when, with the exception of respiration which remained depressed, a progressive adaptation was observed over the course of the study. There were no negative effects on body weight, body temperature, motor function, bowel or bladder function, or clinical pathology values. After 28 days of continuous infusion, the dogs were deeply anesthetized and terminated. Cisternal cerebrospinal fluid taken at termination displayed no clinically significant differences in protein or glucose concentration. All groups, including control, had dogs which had a chronic inflammatory response in the epidural space, as represented by fibrosis, foreign body giant cells, and lymphocytes, but no spinal cord pathology. Both the steady-state plasma and CSF concentrations of clonidine were proportional to the dose; the ratio of CSF to plasma concentration was approximately 0.5. The failure to see any change in CSF composition, significant spinal cord pathology, or signs of tissue or organ toxicity emphasizes the safety of epidurally administered clonidine at infusion rates up to 320 micrograms/hr and at infusate concentrations up to 2 mg/ml.

Inhalation toxicity of aerosolized pentamidine isethionate in rats and dogs.

The toxicity of inhaled aerosolized pentamidine isethionate solutions in rats and dogs was evaluated. Nose-only exposure equipment and a mass mean aerodynamic particle size of < or = 2 microns were employed. Rats received either a single inhaled dose estimated at 0, 1.4, 2.1, or 6.0 mg/kg/exposure day or 4 inhaled doses evenly spaced over 13 weeks estimated at 0, 0.35, 0.7, or 1.4 mg/kg/exposure day. Dogs were administered a single inhaled dose estimated at 0, 1.1, 3.4, or 5.0 mg/kg/exposure day. Rats administered a single inhaled dose of 6.0 mg/kg/exposure day exhibited respiratory distress. The lung-with-trachea weights of these animals were elevated relative to controls. The histopathology of acutely exposed rats consisted of dose-related neutrophil infiltration in the turbinates, larynx, and bronchi; erosion of epithelium in the turbinates and larynx; thickening of the alveoli walls with alveolar accumulation of mononuclear cells and neutrophils; and rhinitis. Rats in the highest dose group in the subchronic evaluation exhibited decreased body weight gains and reduced lung-with-trachea-to-body weight ratios relative to controls. Hematology, clinical chemistry, and urinalysis values were within normal ranges. Microscopic pulmonary tissue changes were similar to those found in acute exposure with certain lesions (e.g., mucous cell hyperplasia) suggestive of a more chronic process. In addition, lung fibrosis was seen at the highest dose. In dogs, pentamidine isethionate did not cause a change in the respiratory minute volume (not measured in rats). Elevated lung-with-trachea weights were noted in the high- dose females. Hematology, clinical chemistry, and urinalysis values were within normal ranges.(ABSTRACT TRUNCATED AT 250 WORDS)

Subchronic (13-week) toxicity studies of N,N-dimethylaniline administered to Fischer 344 rats and B6C3F1 mice.

The subchronic toxicity of N,N-dimethylaniline (DMA) was studied by administration in corn oil by gavage at doses of 31.25, 62.5, 125, 250, 20, or 500 mg/kg body weight to groups of 10 male and 10 female F344 rats and B6C3F1 mice 5 d per week for 13 wk. No compound-related mortality was noted in either rats or mice. Significant decrease in body weight gain was observed in male rats at 250 and 500 mg/kg. The body weight gain of female rats and female mice was not adversely affected by the treatment. Clinical signs of toxicity (cyanosis and decrease in motor activity) occurred in both species and sexes in a dose-dependent fashion. Splenomegaly was observed in all treated groups of rats and mice, with the severity being dose-related. Microscopic examination revealed the presence of hemosiderin in the spleen, liver, testes, and kidney of treated rats and mice. Bone marrow hyperplasia and increased hematopoiesis in the spleen occurred in treated rats, and hematopoiesis was increased in the spleen and liver of treated mice. The severity of these lesions was dose-related. A no-observable-effect for mice was estimated at 31.25 mg/kg; however, a no-effect level was not reached in rats in this study. This suggests that rats are more sensitive than mice to the toxic effect of DMA.

The sanctity of the upper lid in lower eyelid reconstruction questioned. A modification of a lid sharing procedure with a long-term follow-up.

Sharing techniques using the upper eyelid to reconstruct the lower one have been criticised for causing distortion of the normal upper lid leading to corneal exposure and possible visual disturbance, and for creating second-rate lids. A modification of previously described tarsoconjunctival flap techniques is described which minimises the known complications of earlier methods. A flap of conjunctiva alone is mobilised from the upper eyelid and covered with a full thickness skin graft. A second minor procedure to divide the flap from its donor site is necessary 2 weeks later. Forty-three patients over a 25-year period have undergone total lower eyelid reconstruction with this modified technique and are reviewed with some illustrative cases. Total or subtotal lower eyelid reconstruction is most commonly performed following tumour resection and only occasionally to correct congenital or traumatic defects. The surgical techniques available still cause controversy (Byrd, 1983). An upper lid sharing technique has been criticised for possibly causing a shortened or distorted normal lid (Mustardé, 1981). A modification of this method is described which has been used for over 25 years and has reduced the morbidity of the procedure, leading to acceptable cosmetic and functional long-term results.

A clinical trial of BCG immunotherapy as an adjunct to surgery in the treatment of primary malignant melanoma.

A preliminary analysis of a controlled trial of BCG immunotherapy as an adjunct to surgery in the treatment of primary malignant melanoma has been carried out. The length of follow-up varied from 5 years to 6 months. No obvious benefit from BCG immunotherapy has been found so far. On the other hand the treatment is painful with an appreciable morbidity. Skin tests for delayed hypersensitivity have shown no recognisable differences in patients treated with surgery and those who also had BCG, or in the pattern of responses in those who developed recurrences and those who did not. In view of these early findings trial entry has been closed.

Biotransformation products of 3,4,4'-trichlorocarbanilide in rat, monkey, and man.

3,4,4'-Trichlorocarbanilide (TCC), uniformly labeled with 14C in the monochloro ring, was administered to rats, rhesus monkeys, and humans. Radioactive materials in the plasma and urine of all three species and in the bile of rats and monkeys were separated by high performance liquid chromatography. The chromatography showed great similarity between the monkey and the human. Principal metabolites common to all species were the sulfate and glucuronide conjugates of 2'-, 3'-, and 6-hydroxy-TCC. The rat also produced the glucuronide and sulfate conjugates of 2',6-dihydroxy-TCC. The major urinary excretion products found in humans and monkeys were the N- and N'-TCC glucuronides.

The absorption, excretion, and biotransformation of 3,4,4'-trichlorocarbanilide in humans.

The metabolism and disposition of 14C-TCC (3,4,4'-trichlorocarbanilide) have been evaluated in humans following oral exposure to 2.2 mumol/kg body wt. Fecal elimination (70% of dose) was complete 120 hr after dosing and the urinary excretion (27% of dose) was completed in 80 hr. The maximum plasma level occurred 2.8 hr after dosing and was 3.7 nmol-equivalents of TCC per g of plasma (approximately 1.2 ppm). Biotransformation of TCC was rapid but did not appear to involve splitting of the basic TCC structure. The major plasma metabolites were N- and N'-glucuronides of TCC which were eliminated with t1/2 approximately 2 hr to the urine and 2'-hydroxy-TCC sulfate and 6-hydroxy-TCC sulfate (the o-hydroxy-TCC sulfates) which were removed with t1/2 approximately 20 hr (presumably into the bile). It is concluded that a nonradioactive analytical method based on the urinary excretion of the N-glucuronides would be suitable for the determination of TCC absorption in humans.