National Toxicology Program

National Toxicology Program
https://ntp.niehs.nih.gov/go/RDGT96002-01abs

Abstract for RDGT96002 on 3'-Azido-3'-Deoxythymidine and Clarithromycin Combination

ABSTRACT

Reproductive, Developmental, and General Toxicity Study of 3-Azido-3'-Deoxythymidine (CAS No. 30516-87-1) and Clarithromycin (CAS No. 81103-11-9) Combinations in Swiss CD-1 Mice

Report Date: Feb. 23, 1998

Abstract

The toxicity of combinations of AZT (200 or 400) mg and clarithromycin (500, 1250, or 2500 mg) was evaluated in Swiss (CD-1) mice treated by oral gavage. Doses of AZT were equivalent to approximately two and four times the therapeutic dose in humans. Doses of clarithromycin were approximately two, four, and 10 times the human therapeutic dose. Male mice (10 to 18/dose group) were dosed from study day 5 until the day prior to sacrifice on study day 25 or 26. Females were divided into two groups designated females-A and females-B. The females-A (20 to 28/group) were dosed from day 0 to sacrifice. They were cohabited with treated males on days 9-13 to test for effects on mating behavior, fertilization, and implantation, and Caesarean sections were performed on days 28-32. The females designated as females-B (approximately 20/group) were cohabited with untreated males on days 0-4. Sperm-positive females-B were dosed during organogenesis on days 6-15 of presumed gestation and sacrificed on day 4 of lactation.

Summarized in Table 1 are the most significant effects of treatment with AZT and clarithromycin. Administration of AZT alone resulted in slight hematopoietic toxicity manifested by mild declines in RBC, HGB, and HCT values. Hematopotetic cell proliferation and increased hemosiderin deposition in the spleen accompanied the mild alterations in erythrocyte parameters.

Administration of clarithromycin alone resulted in toxicity in multiple vital organs including the liver, spleen, bone marrow, kidney, heart, and brain. Other treatment-related lesions occurred in the thymus, lymph nodes, stomach, and salivary gland. Diminished body weights and a 100% mortality rate occurred in male and female-A mice in the highest dose group. Elevated BUN and creatinine levels accompanied the renal lesions and elevated ALP, ALT, AST, and bile acid values accompanied the liver toxicity. Extensive cytoplasmic vacuolization of phagocytic cells occurred in the majority of the tissues with lesions.

Administration of AZT in combination with clarithromycin resulted in severe hematotoxicity in male and female-A mice and the severity of the anemia was far greater than that induced by AZT alone. The anemia contributed to high mortality rates and was accompanied by extensive atrophy of the bone marrow and splenic red pulp. The anemia was characterized as a moderate nonregenerative macrocytic anemia which progressed to a severe microcytic nonregenerative anemia in the higher dose combination groups. Neutrophilia, lymphopenia, reticulocytopenia, and sporadic thrombocytosis were also considered to be treatment-related manifestations of hernatopoietic toxicity. In general, the morphological alterations in other tissues with lesions were similar to those induced by clarithromycin alone, with extensive cytoplasmic vacuolization of phagocytic cells.

Inflammatory lesions in the forestomach and glandular stomach occurred in several mice of both sexes treated with the higher doses of clarithromycin alone or in combination with AZT. In general, the severity of these lesions increased dramatically when complicated by the presence of fungal organisms. The antibacterial action of clarithromycin likely altered the normal flora in the stomach lumen, which subsequently allowed the fungal overgrowth. Chronic dilatation of the stomach with the large volume of thick gavaged material may have predisposed the stomach to the initial inflammatory lesions.

Treatment with AZT alone resulted in reduced live litter size, an increase in the number of resorptions, and a slight decline in total weight per litter. Treatment with clarithromycin alone resulted in diminished fertility with a reduction in the number of litters delivered, diminished litter size, and a decrease in the number of pups surviving. Fertility was further reduced in groups treated with combinations of AZT and clarithromycin (200 or 400 mg of AZT + 1250 or 2500 mg of clarithromycin). Live litter size was reduced and the average number of resorptions per litter was increased in groups treated with 200 or 400 mg of AZT + 500 mg of clarithromycin but not in the group treated with 500 mg of clarithromycin alone, indicating potentiation with the combination treatment. Prominent declines in fetal weight per litter also occurred in groups treated with combinations of AZT and clarithromycin.

Table 1: Summary of Significant Treatment-Related Toxicological Parameters in the Reproductive/Developmental and General Toxicity Study of AZT/Clarithromycin
Body Weights
Treatment Regimen Males Females–A Females–B
AZT Alone no body weight change decrease in body weight no body weight change
Clarithromycin Alone decrease in body weight decrease in body weight decrease in gestational body weight
AZT + Clarithromycin decrease in body weight decrease in body weight decrease in gestational body weight
Clinical Pathology
Treatment Regimen Males Females–A Females–B
AZT Alone – mild decrease in RBC, HGB, and HCT
– mild increase in MCV and RDW
– mild decrease in RBC, HGB, and HCT
– mild increase in MCV and RDW
mild increase in MCV and RDW
Clarithromycin Alone mild neutrophilia – neutrophilia
– reticulocytopenta
– decreased MCV
– leukocytosis
– increase in BUN and creatinine
– increase in ALP, ALT, AST, and bile acids
– reticulocytopenia
– decreased MCV
AZT + Clarithromycin – anemia
– increased MCV in lower dose groups
– decreased MCV in higher dose groups
– reticulocytopenia
– thrombocytosis
– neutrophilia
– lymphopenia
– increased RDW
– increased in ALP, ALT, AST, and bile acids
– anemia
– increased MCV in lower dose groups
– decreased MCV in higher dose groups
– reticulocytopenia
– thrombocytosis
– neutrophilia
– lymphopenia
– increased RDW
– increase in BUN and creatinine
– increased in ALP, ALT, and bile acids
– increased MCV
– increased RDW

Histopathology
Treatment Regimen Males Females–A
Clarithromycin Alone Liver
– hepatocellular cytoplasmic alteration (slight)
Spleen
– hematopoietic cell proliferation (slight); hemosiderosis (slight)
 
Liver
– hepatocellular cytoplasmic alteration (slight)
Spleen
– hematopoietic cell proliferation (slight); hemosiderosis (slight)
 
Clarithromycin Alone Liver
– cytoplasmic alteration
– hepatocyte necrosis
– cytoplasmic vacuolization
Spleen
– red pulp atrophy
– lymphoid follicle depletion
Bone marrow
– depletion
Kidney
– nephropathy
Lymph nodes
– depletion
Thymus
– atrophy
Brain, choroid plexus
– cytoplasmic vacuolization
Heart
– cytoplasmic vacuolization of valve
– degeneration of atrium
– necrosis of myocardium
Glandular stomach
– cystic degeneration
Stomach
– fungal infection
Salivary gland
– necrosis
Liver
– cytoplasmic alteration
– hepatocyte necrosis
– cytoplasmic vacuolization
Spleen
– red pulp atrophy
– lymphoid follicle depletion
Bone marrow
– depletion
Kidney
– nephropathy
Lymph nodes
– depletion
Thymus
– atrophy
Brain, choroid plexus
– cytoplasmic vacuolization
Heart
– cytoplasmic vacuolization of valve
– degeneration of atrium
– necrosis of myocardium
Glandular stomach
– cystic degeneration
Stomach
– fungal infection
Salivary gland
– necrosis
AZT + Clarithromycin Liver
– cytoplasmic alteration
– hepatocyte necrosis
– cytoplasmic vacuolization
Spleen
– lymphoid follicle depletion
– red pulp atrophy
– hemosiderosis
Bone marrow
– depletion
Kidney
– nephropathy
Lymph nodes
– depletion
Thymus
– atrophy
Brain, choroid plexus
– cytoplasmic vacuolization
Heart
– cytoplasmic vacuolization of valve
– degeneration of atrium
– necrosis of myocardium
Glandular stomach
– cystic degeneration
Stomach
– fungal infection
Salivary gland
– necrosis
 
Liver
– cytoplasmic alteration
– hepatocyte necrosis
– cytoplasmic vacuolization
Spleen
– lymphoid follicle depletion
– red pulp atrophy
– hemosiderosis
Bone marrow
– depletion
Kidney
– nephropathy
Lymph nodes
– depletion
Thymus
– atrophy
Brain, choroid plexus
– cytoplasmic vacuolization
Heart
– cytoplasmic vacuolization of valve
– degeneration of atrium
– necrosis of myocardium
Glandular stomach
– cystic degeneration
Stomach
– fungal infection
Salivary gland
– necrosis
Note: Histopathological evaluations were performed only on gross lesions in Female-B mice.
Reproductive/Developmental
Treatment Regimen Females–A Fetuses Females–B Pups
AZT Alone – reduced live litter size
– increased number of resorptions
– slight decline in fetal weight per litter
no adverse effects
Clarithromycin Alone – reduced live litter size
– no conceptuses
– delivered in high dose group
– slight decline in total weight per litter
– decreased number of litters delivered in high dose groups
– decreased litter size
– decreased number of pups surviving to postnatal day 4
– reduced pup weight/litter
AZT + Clarithromycin – reduced live litter size
– increased number of resorptions
– no conceptuses delivered in highest combination groups
– prominent decline in total weight per litter
 
– decreased incidence of pregnancy
– decreased number of litters delivered in highest dose groups
– decreased litter size
– decreased number of pups surviving to postnatal day 4
– reduced pup weight/litter
– increased duration of gestation

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