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    ACESULFAME POTASSIUM

    Explanation

         Acesulfame K (synonyms: Acesulfam K; Potassium salt of
    6-methyl-1, 2,3-oxathiazine-4(3H)-one-2,3-dioxide; Potassium salt of
    3,4-dihydro-6-methyl-1,2,3-oxathiazine-4-one-2,2-dioxide; Acetosulfam) 
    is an artificial sweetener, approximately 200 times sweeter than
    sugar. It is a white, odourless, crystalline powder with the following
    chemical structure:

    CHEMICAL STRUCTURE 1

         It is proposed for use as a table-top sweetener, and for use in
    soft drinks, fruit preparations, desserts, breakfast cereals, chewing
    gum, and other food applications appear to be possible. Based on data
    for food consumption in the Federal Republic of Germany, and estimated
    levels of use in these specified foods, the probable mean daily intake
    has been estimated as 470 mg/day (Anon., 1980a).

         Acesulfame K is stable in foods, beverages and cosmetic
    preparations under normal storage conditions. Under extreme conditions
    of pH and temperature, detectable decomposition may occur leading to
    the formation of acetone, CO2, and ammonium hydrogen sulfate, or
    amido-sulfate, as final decomposition products; under acid (pH 2.5)
    conditions, minute quantities of acetoacetamide and acetoacetamide
    N-sulfonic acid are formed as unstable intermediate decomposition
    products, while under alkaline (pH 3-10.5) conditions, acetoacetic
    acid and acetoacetamide N-sulfonic acid can be detected.

         This artificial sweetener was assessed for the first time by the
    Joint Expert Committee on Food Additives.

    BIOLOGICAL DATA

    BIOCHEMICAL ASPECTS

    Absorption, distribution and excretion

         Single oral doses of 10 mg 14C-acesulfame K/kg bw given to rats
    and dogs were rapidly absorbed. Maximum blood levels reached were
    0.75  0.2 g/ml in rats, 0.5 h after dosing, and 6.56  2.08 g/ml in
    dogs, 1-1.5 h after dosing. In rats, 82-100% of the dose, and in dogs,
    85-100% of the dose was excreted in the urine; in both species,
    97-100% of their total radioactivity was excreted in faeces, and total
    recovery approximated to 100%.

         Rats given 10 consecutive daily doses of 10 mg/kg orally did not
    show evidence of accumulation. Three days after dosing, the 
    concentration in the organs and plasma was 0.4 nMol/g in liver, and
    less than 0.2 nMol/g in other tissues. Seven days after dosing, the
    concentration in dogs was less than 0.2 nMol/g in all tissues examined
    (Kellner & Christ, 1975a).

         After intravenous administration of a single dose of 10 mg
    14C-acesulfame K/kg bw to rats, the radioactivity was excreted
    quantitatively in urine and the plasma half-life was 0.23 h (Kellner &
    Christ, 1975a).

         Following oral administration of a single dose of 3.6-4.5 mg
    14C-acesulfame K/kg bw to pigs, maximum blood levels ranged between
    0.35-0.72 g/ml between 1-2 h after dosing and fell to undetectable
    levels within 48 h. Excretion occurred mainly in the urine (Kellner &
    Christ, 1975b).

    Bio-transformation

         The metabolism of Acesulfame K was investigated in the urine and
    faeces of rats and dogs which had received single oral doses of
    10 mg/kg bw, and in the urine and bile of pigs dosed orally with
    5 mg/kg bw. The analytical methods used (thin-layer chromatography,
    mass spectrometry and isotope dilution) detected only the original
    substance in these samples (Volz, 1975).

    Effects on enzymes

         In vitro studies on acetoacetamide, a possible minor breakdown
    product of Acesulfame K, showed that it did not function as a
    substrate for thiolase, -hydroxyacyl-CoA-dehydrogenase, and
    -hydroxybutyrate-dehydrogenase indicating that in vivo formation of
    acetamide is not probable (Anon., 1980b).

    Effects on bacteria

         Acesulfame K was without antibacterial activity against 12
    bacterial strains in vitro, and did not show antibacterial activity
    in experimental septicaemia in the mouse with Streptococcus pyogenes
    A77 or Salmonella typhimurium. Long-term culture (30 daily passages)
    of Staphylococcus aureus and E. coli with a range of
    concentrations of Acesulfame did not affect growth characteristics nor
    sensitivity towards antibiotics, ampicillin, cephalothin, tetracycline
    or gentiamycin (Schrinner & Limbert, 1977).

    Nitrosation of Acesulfame K

         In vitro studies were performed to investigate whether
    Acesulfame K could form N-nitroso derivatives. Nitrosation was carried
    out using N2O3 in glacial acetic acid, or excess NaNO2, at pH 3 and
    pH 1. An N-nitroso compound was detected in low yield with N2O3 or
    with nitrite at pH 1 but not at pH 3. The yield at pH 1 was estimated
    to be 0.4  10-3% (Eisenbrand, 1979).

    TOXICOLOGICAL STUDIES

    Special studies on acetoacetamide - acute toxity and mutagenicity

         The oral LD50 of acetoacetamide in female rats was greater than
    15 g/kg bw (Anon., 1977).

         Acetoacetamide was non-mutagenic in bacterial assays using four
    strains of Salmonella typhimurium, with and without metabolic
    activation (Gericke, 1977), did not induce point mutations in cultured
    V79 Chinese hamster cells, and was negative in the cell transformation
    assay using M2 mouse fibroblasts (Marquardt, 1978).

    Special studies on -hydroxybutyramide - mutagenicity

         -Hydroxybutyramide, a metabolite of acetamide in some mammalian
    species, was non-mutagenic in the Ames' test against four strains of
    Salmonella typhimurium, with and without metabolic activation
    (Engelbart, 1979).

    Special study on caecal enlargement

         These studies were performed to investigate the possible
    reversibility of caecal enlargement observed in short-term and
    long-term studies.

         Groups of 10 juvenile female Wistar rats, body weight
    approximately 115 g, received Acesulfame K at dietary concentrations
    of 0, 3.0, or 10.0% for treatment periods of 45, 49, and 90 days. One
    group from each dose level was sacrificed at the end of the treatment
    periods of 45 and 90 days; in addition one group from each dose level
    was sacrificed after recovery periods of 41 days' treatment, and 14,
    56 and 127 days following 90 days treatment. Food and water intake,
    and body weight were measured weekly. At termination, the weights of
    caeca with and without contents, as well as moisture content of the
    contents, were determined.

         At the 10% feeding level, there was an increase in food and water
    intake and a reduction in body weight gain which was reversible during
    the post-treatment period. At this treatment level, filled caecal

    weight relative to body weight was approximately doubled after 45 and
    90 days while at the 3% dietary level, a significant increase of about
    30% was observed after 90 days only. A significant increase in the
    water content of caecal contents was observed only in the highest dose
    group.

         The changes in the caecal weights after 90 days' exposure to 3%
    Acesulfame K in the diet were reversible within 14 days. After 90
    days' treatment at the 10% dietary level, the water content in the
    caecum returned to normal within 14 days but the filled caecal weight
    remained significantly increased (by approximately 30%) even after a
    recovery period of 127 days (Mayer et al., 1978b).

         A similar study was performed with adult female Wistar rats,
    body weight approximately 220 g. Initially, animals receiving 10%
    Acesulfame K in the diet experienced anorexia followed by an increased
    food consumption after two weeks. Water consumption was increased
    during the treatment period in both dose groups.

         Filled and empty caecal weights were increased by 80% and 33%
    respectively in animals receiving 10% Acesulfame for 45 days.
    Increased caecal weights were observed in both dose groups after 91
    days' treatment. Caecal water content was significantly increased in
    both dose groups after 45 days but not after 91 days' treatment.

         All the changes were reversible in animals of both dose groups
    treated for 49 days followed by a 42 day recovery period. After 91
    days' treatment at the 3% dietary level, all changes were reversible
    within 14 days; at the 10% dietary level, caecal water content
    returned to normal within 14 days but filled caecal weights were still
    significantly increased (by about 30%) after a recovery period of 127
    days (Mayer et al., 1978c).

         These experiments did not reveal any significant differences
    between juvenile and adult animals with regard to induction or
    reversibility of caecal enlargement. Complete reversibility was
    demonstrated at the 3% dietary level, but not at 10% in the diet. The
    authors note that the coincidence of increased water intake with
    increased caecal water content and the reversibility of both of these
    parameters after withdrawal of Acesulfame K probably indicates that
    the changes are of osmotic origin.

    Special studies on carcinogenicity

         Four groups of 100 male and 100 female Swiss mice were fed diets
    containing 0, 0.3, 1.0, or 3.0% Acesulfame K for 80 weeks. All
    survivors were sacrificed and autopsied, and weights of livers and
    kidneys were recorded. All tumours and tissues showing gross lesions  
    suspected of being tumours and the livers of all animals were examined
    microscopically (haematoxylin and eosin sections).

         The feeding of Acesulfame K did not cause adverse effects on
    general appearance, behaviour or survival at any of the dietary levels
    but body weights were slightly decreased at the 3.0% dose level in
    both sexes. The relative liver weight was decreased at all dose levels
    in males only but there was no evidence of a dose-related response.
    Deaths occurring during the course of the study were attributed to
    chronic nephropathy, severe liver degeneration, respiratory infections
    and lung tumours.

         Gross and microscopic examination revealed a variety of tumours
    in both test and control animals, but evaluation of the data on type
    of tumour, location and incidence did not indicate that the test
    compound was carcinogenic to mice at dietary levels up to 3% for 80
    weeks (Beems & Til, 1976).

         See also Long-term studies in rats.

    Special studies on mutagenicity

         An oral mutagenicity study (micronucleus test) was carried out in
    which Acesulfame K was administered orally to male and female NMR1
    mice at doses of 450, 1500, and 4500 mg/kg on two consecutive days.
    The animals were killed six hours after the second application, bone
    marrow was taken from the femur and 2000 polychromatic erythrocytes
    per animal counted and scored for micronuclei. The mutagenic index did
    not differ significantly from 1 (Baeder & Horstmann, 1977).

         In a dominant lethal assay, Acesulfame K was administered to male
    Wistar rats at dietary levels of 1.0 or 3.0% for five consecutive days
    prior to mating. At day 1, 8 and 15 post-treatment each male was caged
    with two untreated females for seven days. Pregnant females were
    sacrificed mid-term and scored for pregnancy rate and total and dead
    implants. No adverse effects were observed and it was concluded that
    Acesulfame K at these dietary levels did not induce dominant lethal
    mutations in spermatozoa of vas deferens and epididymis, testicular
    sperm or late spermatids (Willems, 1974).

         Cytogenetic investigations were conducted on bone marrow cells of
    Chinese hamsters treated orally with five consecutive daily doses of
    Acesulfame K of 0, 450, 1500, or 4500 mg/kg bw. The ratios of
    chromosomal abnormalities in control and treated animals were low, and
    values normally found in this strain were not exceeded (Mayer et al.,
    1978a).

         The ability o Acesulfame K and of acetoacetamide to induce
    mutations in V79 Chinese hamster cells in vitro (8-azaguanine
    susceptibility to resistance) was investigated at concentrations of
    10-10 000 g/ml. Neither of the compounds was mutagenic in this
    system; acetoacetamide was slightly cytotoxic at the highest

    concentration. The compounds were also screened for induction of
    transformations in M2 mouse fibroblasts at similar concentrations.
    Acesulfame K did not cause any transformations, but reduced plating
    efficiency (cytotoxicity) was observed at concentrations of 5000 and
    10 000 g/ml; one (out of 14) transformed focus was observed with
    acetoacetamide at a concentration of 5000 g/ml but not at the higher
    concentration, and this was not considered to be evidence of potential
    oncogenic activity. In addition, Acesulfame K was not mutagenic nor
    cytotoxic against four strains of Salmonella typhimurium at
    concentrations up to 100 mg/plate (Marquardt, 1978).

         Acesulfame K was neither mutagenic nor cytotoxic in the Ames'
    test using four strains of Salmonella typhimurium (detecting both
    base-pair and frame-shift mutations) either with or without activation
    by rat microsomes (Rohrborn, 1976).

    Special studies on pharmacological aspects

         Dosages of Acesulfame K of 400 m/kg i.p., 500 m/kg orally, or
    320 mg/kg subcutaneously, did not depress motor activity of mice
    excited by Pervitin. The hexobarbital sleeping time in mice was not
    changed by pretreatment with Acesulfame K at doses of 500 mg/kg
    per os or 160 mg/kg subcutaneously. Metrazol-induced convulsions in
    mice were not influenced by Acesulfame K at doses of 500 mg/kg
    per os, 300 mg/kg i.p., or 320 mg/kg subcutaneously; anti-convulsant
    activity can thus be excluded. Administration of Acesulfame K
    (200 mg/kg i.p.) to mice was without effect on tetrabenazine-induced
    ptosis and catalepsy, thus the compound is without anti-depressant
    properties. Acesulfame K (200 mg/kg i.p., 160 mg/kg s.c., or 500 m/kg
    per os) was without effect on compulsive gnawing behaviour induced by
    the combined application of apomorphine and imipramine, therefore
    antidepressant and anticholinergic effects are unlikely. At doses of
    320 mg/kg s.c. or 500 mg/kg orally, Acesulfame K had no analgesic
    effect on mice.

         Predosing of rats with Acesulfame K (500 mg/kg orally or
    160 mg/kg s.c.) was without anti-inflammatory effect on Aerosil-
    induced paw oedema, and similar doses had no antipyretic effect in
    rats with yeast-induced fever. Eight daily doses of Acesulfame K
    (0-100 mg/kg) per os had no effect on serum cholesterol, total
    glycerol, free glycerol or glucose levels; relative liver weights were
    unchanged. In acute tests, Acesulfame K had no effect on blood sugar
    levels in rats given 100 mg/kg orally, guinea-pigs given a similar
    dose i.p., or rabbits receiving 100 or 500 mg/kg orally or 50 mg/kg
    i.v.  Acesulfame K had no diuretic effect in rats and dogs at oral
    dose levels of 50 mg/kg and 20 mg/kg respectively.

         Acesulfame K given intravenously to guinea-pigs at a dose level
    of 24 mg/kg reduced digoxin toxicity. This effect was due to the
    potassium content and not to antiarrhythmic activity of the compound.
    Intravenous administration of 1-5 mg Acesulfame K/kg to anaesthetised
    guinea-pigs one minute before treatment with histamine was without
    effect on the bronchial musculature.

         Cardiovascular experiments in anaesthetized dogs showed that
    intravenous administration of Acesulfame K was without effect up to a
    dose of 6 mg/kg; doses of 12 and 24 mg/kg caused a decrease in
    contractility of the heart with a transient reduction of blood
    pressure and peripheral blood flow. The changes were compensated for
    in 3-5 minutes. Intraduodenal administration of Acesulfame K to
    anaesthetized dogs at dose levels of 0-1000 mg/kg induced a slight
    reduction of blood pressure at 500 mg/kg and this was accompanied by a
    reduction of cardiac contractility of about 20% at 1 g/kg. The effect
    was reversed in 50-80 minutes and other cardiovascular parameters were
    unchanged. In the conscious dog, after a five day treatment with
    Acesulfame K at 100 mg/kg per os daily, no change in blood pressure
    or cardiac activity could be detected. Acesulfame K at doses of
    0-24 mg/kg i.v. had no anti-arrhythmic effect on anaesthetised dogs
    poisoned with K-strophanthin. Daily oral administration of Acesulfame
    K (1 g/kg) to dogs for 14 days was without effect on thromboplastin
    time, thrombin time, recalcification time and thromboelastography of
    plasma samples.

         No functional changes were detected after application of 50 g
    Acesulfame K to isolated guinea-pig heart using the Langendorff
    techniques; the compound did not show antiarrhythmic activity
    in isolated, perfused guinea-pig heart with aconitine and
    digitoxin-induced fibrillation. In the isolated ileum of guinea-pig,
    Acesulfame K at a concentration of 10 g/ml had no neurotropic or
    spasmolytic effect on smooth muscle.

         Addition of Acesulfame K to dog plasma in vitro was without
    effect on thrombin time, thromboplastin time or recalcification time.

         Investigation of the carbonic anhydrase-inhibiting effect
    in vitro showed that Acesulfame K had virtually no effect,
    concentrations of 180 mg/ml being required for 50% inhibition (Vogel &
    Alpermann, 1974).

    Special studies on the short-term toxicity of potassium chloride

         Feeding studies in rats with potassium chloride were conducted to
    elucidate the possible involvement of the potassium ion in Acesulfame
    K in changes observed in toxicological studies. Three groups of 20
    male and 20 female weanling Wistar rats were fed for 90 days on diets
    containing 0, 12 000 or 37 000 ppm (0, 1.2 or 3.7%) KCl, equivalent to
    the potassium content of diets containing 0, 3, or 10% Acesulfame K.

    Regular measurements were made of body weight, food and water
    consumption, urinary volume and potassium content. After the animals
    had been sacrificed, the caeca with and without contents were weighed
    and the water content of the caecal contents were determined.

         There was a dose-related increase in water consumption in both
    sexes throughout the study and, in the first few weeks, the food
    consumption of treated animals was slightly lower than that of
    controls. Body weight gains were depressed in males of both
    concentration groups throughout the 90 day period but in females
    statistically significant differences were obtained only up to the
    twenty-ninth day. Dose-related increases in urine volumes and urinary
    potassium were observed. Filled caecal weights were increased by about
    10% in males and 20% in females of the top dose group, but these
    differences were not statistically significant; no differences were
    observed in empty caecal weights, nor in water content of the caecal
    contents. It was concluded that the potassium content of Acesulfame K
    could be responsible for some adverse effects seen in toxicological
    studies, particularly depressed body weight gain (Mayer et al.,
    1978d).

    Special studies on reproduction

         A multigeneration study in rats was carried out, in which males
    and females received Acesulfame K at dietary levels of 0, 0.3, 1.0 and
    3.0% for three successive generations, each comprising two consecutive
    litters. A teratogenicity study was conducted with 15 females per
    group of the F2b and F3a generations. Rats from the F3b generation
    were submitted to clinical and pathological examination. Pups from the
    F1a litters were used for a chronic toxicity/carcinogenicity study at
    the same dietary levels of Acesulfame K as the parents (see Long-term
    studies).

         Fertility, number of young per litter, birth weight, growth rate
    and mortality during the lactation period were not adversely affected
    and there were no indications of increased mortality in utero.

         Growth rate was slightly decreased in the top dose group of the
    F0 and F1 generations, and the mid-dose group of the F0 generation.

         In the teratogenicity studies, no adverse effects were seen in
    appearance, food consumption, autopsy of the dams, organ weights, or
    litter data; no visceral or skeletal abnormalities attributable to the
    treatment were observed.

         In a four-week feeding study on rats of the F3b generation, body
    weights and food efficiency figures were slightly decreased in males
    at the highest dose level. The relative weights of the caecum were
    slightly increased in both sexes of the high-dose group and in males
    of the mid-dose group. Gross and microscopic examination did not
    reveal any treatment-related pathological changes (Sinkeldam et al.,
    1976).

         In a separate study, Acesulfame K was fed to pregnant rats at
    dietary levels of 0, 0.3, 1.0, or 3.0% from day 6 up to and including
    day 15 of pregnancy; a positive control group received 75 000 i.u.
    vitamin A/rat/day during the same period. An increase in food
    consumption was observed at all three dose levels of Acesulfame K,
    most pronounced in the 0.3% group. Mean foetal weight showed a slight,
    dose-related increase in the test groups but skeletal and visceral
    examination of the foetuses revealed no teratogenic effects
    attributable to the feeding of Acesulfame K. A wide range of
    abnormalities was induced by teratogenic doses of vitamin A in
    positive controls (Koeter, 1975).

         A reproduction study was carried out in which male and female
    rats were fed diets containing 0, 0.3, 1.0, or 3.0% Acesulfame K for
    12 weeks prior to mating; the dams received the same diet throughout
    pregnancy and lactation. Observations were made on the fertility
    of the females, number of young per litter, sex rates, gross
    abnormalities, mortality, body weight, and resorption quotient. Growth
    rate was slightly decreased in parent rats of the top dose group and
    in the mid-dose group females. No dose-related effects were seen in
    any of the observations made on the offspring, and there were no
    indications of increased mortality in utero.

         At weaning, 60 animals of each sex were selected from the litters
    for a two-year feeding study (see below, Long-term studies)
    (Sinkeldam, 1976).

         An embryotoxicity study with Acesulfame K was carried out in
    which female rabbits received doses of 0, 100, 300 or 900 m/kg bw by
    gastric intubation from the seventh to the nineteenth day after
    mating. On the twenty-ninth day of pregnancy, foetuses were delivered
    by Caesarean section; live and dead foetuses, resorptions and
    placentas were counted, weighed and examined macroscopically. The
    24-hour survival was determined by incubation and half of the foetuses
    examined for skeletal abnormalities and the remaining half for
    visceral changes. One dam from the 300 mg/kg group had a premature
    birth. All other observations were within the range of control values
    and there was no evidence of compound-related malformations (Baeder &
    Horstmann, 1977).

    Acute toxicity
                                                                  

    Species       Route    LC50 (mg/l)         Reference
                                                                  

    Zebra Fish    Water      >1 000      Markert & Weigand, 1979a

    Golden Orfe   Water      >1 000      Markert & Weigand, 1979b
                                                                  

                           LD50 (mg/kg)
                                                                  

    Rat           p.o.       7 430       Anon., 1973

                  i.p.       2 240       Mayer & Weigand, 1977
                                                                  

    Short-term studies

    Rat

         Four groups of 10 male and 10 female weanling Wistar-derived rats
    were given diets containing 0, 1.0, 3.0, or 10% Acesulfame K for 90
    days. Body weights were recorded weekly, food intake was determined
    during the first four weeks and in weeks 11 and 12. In week 13, the
    animals were bled from the tip of the tail and blood samples were
    examined for haemoglobin content, haematocrit, RBC and total and
    differential white cell counts. Pooled urine samples from each group
    were collected in week 13 and examined for appearance, pH, glucose,
    protein, occult blood, ketones and microscopy of the sediment. At
    autopsy, blood samples were examined for SGPT, SGOT, alkaline
    phosphatase, total serum protein and serum albumin. Organ weights were
    recorded for heart, kidneys, liver, spleen, brain, testes/ovaries,
    thymus, thyroid, adrenals and caecum (filled and empty). Histological
    examination was carried out on haematoxylin/eosin sections of the
    weighed organs and of lung, salivary glands, trachea, aorta, skeletal
    muscle, axillary and mesenteric lymph nodes, pancreas, bladder,
    prostate, epididymis, uterus, mammary gland, oesophagus, stomach,
    duodenum, ileum and colon.

         Food consumption of rats fed Acesulfame K at the 10% level was 
    depressed during the first two to three weeks and body weight gain as
    markedly lowered during the first four weeks; slight diarrhoea and
    increased faecal water content occurred at this dose level. A slight
    increase in haemoglobin concentration was observed in males of the top
    dose group only, and total serum protein was slightly decreased in
    females only. Caecal enlargement was observed in both sexes receiving

    10% Acesulfame K and in females receiving 3%. The relative weights of
    the liver and kidneys were slightly elevated in females of the 10%
    group and relative spleen weights were slightly depressed in all dose
    groups.

         Urinalysis, serum enzyme levels and serum albumin were not
    affected by the treatment, no gross pathological changes were detected
    and no dose-related abnormalities were observed histologically
    (Sinkeldam, Til & Willems, 1974).

         These workers considered that the caecal enlargement was a
    physiological response to the presence of osmotically-active material
    in the gut and that, since liver, kidney and spleen weights were
    within the normal range of the strain of rat used, and no histological
    changes occurred, the no toxic effect level is conservatively placed
    at 3% in the diet; this is equivalent to 1.5 g/kg/day in rats.

    Dog

         Four groups of four female and four male beagle dogs, initially
    17-21 weeks old, were fed diets containing 0, 0.3, 1.0, or 3.0%
    Acesulfame K for two years. Body weight was recorded weekly for the
    first 12 weeks and at four-weekly intervals thereafter. Urinalysis,
    haematological examination and clinical chemistry were performed after
    12, 26, 52, 78 and 104 weeks. Urinalysis included specific gravity,
    pH, sugar, protein, occult blood, ketone and microscopic examination
    of sediment; haematology comprised sedimentation rate, clotting time,
    haemoglobin, PCV, RBC count, WBC count and differential leucocyte
    count; clinical chemical investigations included blood sugar, urea,
    SGOT, SGPT, serum alkaline phosphatase, total serum protein and serum
    albumin. Liver function tests (bromosulfophthalein clearance) and
    kidney function tests (phenol red excretion) were performed on control
    and top dose group animals after 26, 52 and 104 weeks. At termination,
    gross pathological examinations were performed and the following
    organs weighed: heart, kidneys, spleen, liver, lungs, testes/ovaries,
    thyroids, adrenals and brain. Histological examinations were performed
    on the weighed organs and also on the following tissues: spinal cord,
    sciatic nerve, salivary glands, skeletal muscle, thoracic aorta, skin,
    tonsils, axillary, superficial, cervical and mesenteric lymph nodes,
    bladder, oesophagus, stomach, duodenum, jejunum, ileum, caecum, colon,
    pancreas, trachea, circumanai glands, eyes, epididymis, prostate,
    uterus, gall bladder, tongue and thymus. A marrow smear (rib bone) was
    also examined. General appearance, condition, behaviour and survival
    were not affected by the treatment. None of the examinations performed
    revealed adverse effects related to the feeding of Acesulfame K.

         The no-toxic effect level was found to be higher than 3% in the
    diet corresponding to an intake of 900 mg/kg/day in dogs (Reuzel & van
    der Heijden, 1977).

    Long-term studies

    Rat

         A combined chronic toxicity and carcinogenicity study was
    performed on Wistar rats (CIVO strain) which were obtained from the
    F1a generation in a multigeneration study (see Special studies on
    reproduction above). Four groups of 60 male and 60 female weanling
    rats were given diets containing 0, 0.3, 1.0, or 3% Acesulfame K for
    two years. The rats were derived from parents which had been
    maintained on the same diet since weaning. Periodic observations were
    made of appearance, behaviour growth and food intake. Haematological
    examinations were carried out after 13, 26, 52, 78 and 104 weeks,
    clinical chemical tests were performed on blood samples after 26, 52
    and 104 weeks and urinalysis was done after 26, 52, 78 and 102 weeks.
    At termination, survivors were autopsied and organ weights recorded
    for heart, kidneys, spleen, liver, brain, gonads, thyroid, adrenals
    and caecum (filled and empty). Tissue samples from 20 male and 20
    female rats of the control and top dose groups only were subjected to
    comprehensive histological examinations; histology on other animals
    was limited to liver, spleen, adrenals, thyroid, parathyroid,
    pituitary and ovaries, and to grossly visible lesions suspected of
    being tumours.

         Body weight gain was decreased in both sexes of the top dose
    group during the first 44 weeks of the study but not significantly
    thereafter. Death-rates of males fed 1.0 or 3% Acesulfame K and of
    females fed 0.3% Acesulfame K were higher than controls but it was
    considered that there was no evidence of mortality being increased by
    treatment, and the mortality of control rats was low for the strain of
    rat used. Interim deaths were mainly due to chronic respiratory
    disease and lymphoreticular malignancies of pulmonary lymphoid tissue.
    The incidence of pulmonary lymphoreticular tumours was relatively high
    in both males and females of the top dose group but only achieved
    statistical significance in females; there was also some evidence that
    these tumours appeared rather earlier in males of the mid and top dose
    groups. The results of haematological, clinical, chemical and
    urinalysis investigations were essentially normal in all dose groups.
    The relative weights of liver, kidneys, caecum and adrenals were
    increased in both sexes of the high dose group but the differences
    only reached statistical significance in the cases of liver and empty
    caecal weight in males, and kidneys and caecal weight in females.
    Gross and histopathology did not reveal any treatment-related effects
    (Sinkeldam et al., 1977).

         In commenting on these results, the authors pointed out the
    problems of inter-group comparisons in multigeneration studies where
    the animals in the different dose groups are not randomised. They
    stated that the increased death rate in test animals was still within

    the normal range for the strain of rats used and the mortality in
    controls was lower than usual. Pulmonary lymphoreticular tumours are a
    common cause of death in the strain of rats used, with very variable
    incidence, and the frequency in the test groups was within the normal
    range. It was concluded that the "higher" incidences and earlier
    appearance in this study were fortuitous findings and did not suggest
    that Acesulfame K possessed carcinogenic properties (Sinkeldam et al.,
    1977).

         A second combined chronic toxicity and carcinogenicity study was
    carried out on a different rat strain with a lower incidence of
    pulmonary tumours in untreated animals. Four groups of 60 male and 60
    female SPF-Wistar rats received diets containing 0, 0.3, 1.0 or 3.0%
    Acesulfame K for 120-123 weeks. The rats used were progeny from
    parents which had been maintained on the same test diets since
    weaning. No adverse effects, other than decreased body weight in the
    top dose group were observed in this study. In particular there was no
    increased mortality nor tumour incidence in the treatment groups. It
    was concluded that Acesulfame K failed to show carcinogenic or other
    effects of toxicological significances when fed to rats at levels of
    up to 3.0% for 120 weeks (Sinkeldam et al., 1979).

    OBSERVATIONS IN MAN

         Three human volunteers, body weight 70-80 kg, were given a single
    oral dose of 30 mg 14C-Acesulfame K in peppermint tea. Absorption was
    rapid and virtually complete, maximum blood concentrations of
    0.28 g/ml occurring after 1 to 1-1/2 h. Elimination occurred rapidly
    with a plasma half-life of 2-1/2 h, over 99% of the dose being
    excreted in urine and less than 1% in faeces; 98% of the activity was
    eliminated in the first 24 h. From the pharmacokinetic data it was
    calculated that repeated doses of 30 mg at 3 h intervals would
    increase the maximum serum levels 1.7-fold and at 2 h intervals
    maximum serum levels would increase 2.4-fold relative to a single dose
    (Christ & Rupp, 1976).

         The metabolism of Acesulfame K was studied in serum and urine
    from human volunteers following a single oral dose of 30 mg per
    individual. Only the original substance was detected in all samples
    (Volz, 1976).

    Comments

         Some shortcomings were apparent in the long-term/carcinogenicity
    studies. The mouse carcinogenicity study was not considered to meet
    current requirements in that detailed histopathology was performed
    only on the livers and on others showing gross lesions suspected of
    being tumours; in the second long-term feeding study in rats, only a
    small proportion of the animals in the control and top dose groups

    were examined histopathologically in detail. Further clarification is
    needed of the report of an increased incidence of lymphomas restricted
    to the lung in the first long-term rat study.

    EVALUATION

    No ADI allocated.

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    See Also:
       Toxicological Abbreviations
       Acesulfame potassium (WHO Food Additives Series 18)
       Acesulfame potassium (WHO Food Additives Series 28)
       ACESULFAME POTASSIUM (JECFA Evaluation)