Pharmacological and Toxicological Evaluation of Orally Administered Pyridostigmine in Dogs

Pharmacological and Toxicological Evaluation of Orally AdministeredPyridostigmine in Dogs. KLUWE, W. M., PAGE, J. G., TOFT, J.D., RIDDER, W. E., AND CHUNG, H. (1990). Fun-dam Appl. Toxicol.14, 40–53. Pyridostigmine bromide, a reversible cholinesteraseinhibitor, was administered orally (capsule gavage) to beagledogs (10–15 months of age) of both sexes once daily at5, 10, or20mg/kg for 14 days; every 8 hrat2 or 5 mg/kg for 28days; or every 8 hr at 0.05,0.5, or 2 mg/kg for 3 months aspart of its preclinical safety assessment. A small portion ofthe dogs receiving pyridostigmine for 3 months were allowedan untreated recovery period of an additional 3 months. Dailydoses of 10 or 20 mg/kg were lethal to some of the dogs whengiven for up to 14 days and caused severe intestinal distress,including diarrhea, emesis, and reddened feces in all animals.The cause of death was intestinal intussusception. Signs ofsystemic toxicity apparent at these doses included hypersalivationand tremors. Similar but less severe effects were produced by5 mg/kg per day, plasma cholinesterase activities were inhibitedby all three doses in a dose-related manner. Signs of toxicityin the 28-day and 3-month studies were generally limited tothe gastrointestinal tract and included diarrhea or soft stoolsand reddened or mucoid-containing stools; these signs appearedto reverse upon discontinuation of the drug. A single dog at2 mg/kg every 8 hr developed an apparent intussusception. Therewere no pathological changes in clinical chemistry, hematology,or urinalysis parameters associated with doses of 0.05, 0.5,or 2 mg/kg every 8 hr for up to 3 months, nor were any drug-relatedlesions observed upon gross necropsy and microscopic evaluationof the major tissues and organs. Red blood cell (RBC) acetylcholinesterase(AChE) activities in the 3-month study were inhibited by approximately10,50, and 70% in the 0.05,0.5, and 2 mg/kg every 8-hr dosegroups, respectively, and these degrees of inhibition were maintainedthroughout the period of treatment. These data suggest thatprolonged oral administration of pyridostigmine at doses sufficientto cause profound and sustained inhibition of RBC AChE activity(i.e., as high as 70%) cause mainly local, gastrointestinaldistress related to altered intestinal motility. At the extreme,this can be manifested as a life-threatening intestinal intussusception.Systemic anticholinesterase effects (other than enzyme inhibition)were observed only at doses of 2 mg/kg and greater, while local(gastrointestinal) effects and inhibition of RBC AChE were observedat doses as low as 0.05 mg/kg.     

Phenotypic Analysis of Lymphocyte Subpopulations in Lymph Nodes Draining the Ear Following Exposure to Contact Allergens and Irritants

The murine local lymph node assay (LLNA) measures in vivo proliferationin draining lymph nodes (DLN) following topical exposure tochemicals to assess contact sensitization potential. However,proliferation has also been observed with some irritants. Tofurther characterize events in the DLN during the LLNA and distinguishallergens from irritants, phenotypic analysis of lymphocytesubsets was made following topical exposure. In preliminarystudies, mice were treated on the ears for 3 consecutive days,and 48 hr following the final application, analysis of CD3,CD4, CD8, and B220 expression was evaluated by flow cytometry.The allergens oxazolone (OXAZ) and picryl chloride (TNCB) andthe irritant benzalkonium chloride (BC) increased cell numbercompared to vehicle. The increase in lymph node cellularityfor these materials was due to an increase in the total numberof T and B lymphocytes. Interestingly, even though contact sensitizationis a cell-mediated immune response (Th1), mice exposed to thecontact allergens showed a preferential increase in B lymphocytesin the DLN as seen by an increase in the percentage of B220⁺cells. The percentage of B220⁺ cells was 13.1 and 36.1% forOXA and TNCB, respectively, compared to percentages of 7.4 and9.3% for irritant and vehicle, respectively. With some allergens,a concomitant decrease in the percentage of CD3⁺ cells was seen.Time course studies demonstrated the increase in the percentageof B220⁺ cells was seen in allergen treated mice by 24 hr afterthe final application of material, plateaued by 48 hr, and wasstill elevated by 96 hr. In allergen-treated mice, percentagesof B220⁺ cells increased dose dependency. Further studies wereperformed to evaluate additional contact allergens and irritantsand determine if evaluation of flow cytometric parameters couldpotentially identify contact allergens and differentiate themfrom irritants. Analysis of data from these studies, which examineda total of five contact allergens and six irritants, showedthat the modifications to the LLNA improved the identificationof irritants and allergens in individual experiments by includingboth phenotypic analysis of the DLN and cell number per nodeas endpoints rather than either endpoint alone.     

BLADDER CANCER IN PATIENTS WITH MULTIPLE SCLEROSIS TREATED WITH CYCLOPHOSPHAMIDE

Purpose

We define the risk of bladder cancer in multiple sclerosis related to the use of indwelling catheters and cyclophosphamide administered as an immunomodulating agent.

Materials and Methods

We retrospectively reviewed the records of 2,351 patients with multiple sclerosis referred to the National Center for Multiple Sclerosis.

Results

Of the 2,351 patients 2 women and 5 men (0.29%) had bladder cancer. Of the 850 chronically catheterized patients the incidence was 0.7%. One patient with cancer performed intermittent catheterization for a rate of 0.23% in this group. In a subgroup of 70 patients treated with cyclophosphamide 5 chronically catheterized patients (5.7%) had bladder cancer. Hematuria was the most common presenting symptom. These data were compared with those in the literature on bladder cancer in spinal cord injury.

Conclusions

These data suggest a possible synergistic role of cyclophosphamide and chronic catheterization in the induction of secondary bladder cancer. Regular cystoscopy is warranted in these patients to allow early detection of bladder tumors. Nitric oxide metabolism may be an important factor in the carcinogenesis of this type of bladder cancer.     

Increased Hyaline Droplet Formation in Male Rats Exposed to Decalin Is Dependent on the Presence of {alpha}2u-Globulin

Increased Hyaline Droplet Formation in Male Rats Exposed toDecalin Is Dependent on the Presence of _2u-Globulin. RIDDER,G. M., VON BARGEN, E. C., ALDEN, C. L., AND PARKER, R. D. (1990).Fundam. Appl. Toxicol. 15, 732–743. A peculiar decalin-inducedmale rat nephropathy associated with the altered renal handlingof filtered protein appears limited to the accumulation of theprotein, _2u-globulin. Several strains of male rats that produce_2u-globulin (Fischer-344, Sprague-Dawley, Buffalo, and NorwayBrown) demonstrate spontaneous renal cortical hyaline dropletswhich are exacerbated after exposure to decalin. In all cases,a close correlation exists between hyaline droplet formationobserved histologically and _2u-globulin accumulation measuredbiochemically. In stark contrast, the NCI-Black-Reiter strain,which does not produce measurable quantities of _2u-globulin,neither forms hyaline droplets nor accumulates any filteredprotein in its kidney cortex either spontaneously or after exposureto decalin. Also, female rats injected ip with male rat _2u-globulinexhibit increased hyaline droplet formation and _2u-globulinaccumulation when treated with decalin. These data provide evidencethat the presence of _2u-globulin is key in understanding whythis nephropathy appears unique to the male rat.