ZD7114, [(S)-4-[2-(2-hydroxy-3 phenoxypropylamine)ethoxyl-N-(2-methoxyethyl
) phenoxyacetamide], and ZD2079, [(R)-N-(2-[4-(carboxymethyl)phenoxy]ethyl)
-N-(beta-hydroxyphenethyl)ammonium chloride], are beta 3-adrenoceptor stimu
lants with selectivity for brown adipose tissue. ZD7144 is the hydrochlorid
e salt of the S-enantiomer of the racemic amide ZD2079. They were developed
as potential novel treatments for obesity and non-insulin-dependent diabet
es mellitus. Male and female rats were dosed separately by gavage for a min
imum of 28 days with 0, 10, 50, and 500 mg/kg/day of ZD7114 or with 0, 10,
30, and 150 mg/kg/day of ZD2079. Two further groups of male and female rats
were dosed with 0 and 500 mg/kg/day of ZD7114 for 28 days and were then al
lowed a 6-wk, undosed withdrawal period. At high doses, both compounds caus
ed urinary tract toxicity, which primarily affected the distal tubules and
collecting ducts of the kidney via tubular necrosis. They also caused urete
ric inflammation, cystitis, and accumulation of crystalline inclusions thro
ughout the urinary tract. As a result of urinary tract toxicity, affected a
nimals from one or both studies showed reduced red blood cell indices, lowe
r platelet counts, and higher white cell counts. Blood chemistry revealed l
ower plasma concentrations of glucose (7.28 +/- 1.37 compared to 8.11 +/- 0
.65 for the control) and total protein (63.42 +/- 3.65 compared to 69.17 +/
- 3.24 for the control) and increased plasma urea (37.15 +/- 19.96 compared
to 8.09 +/- 0.87 for the control). Urinalysis showed an increase in the nu
mber of crystals, blood, and protein. In the urinary tract, the severe crys
talluria with accumulation of crystalline material indicated that this may
have a role in the etiology of the target organ toxicity. Poor solubility o
f the compounds at normal urinary pH was considered a possible mechanism fo
r the crystalluria.