Purpose: To investigate the acute toxicity of ethanol extract of Adenium obesum (Forssk.) Roem. & Schult stem bark in Wistar rats in relation to haematological parameters.

Methods: This involved the administration of single dose of 300 mgkg^-1, 2000 mgkg^-1 and 5000 mgkg^-1 of the extract by oral gavage separately to three different groups of female rats (n = 3) one after another based on the absence of mortality and/or morbidity during a 14-day observation period. The control group was administered distilled water as placebo (1 mL per 100 g body weight).

Results: The exposed rats did not show any obvious signs of toxicity, morbidity or mortality. Median lethal dose (LD₅₀) of the extract was ≥ 5000 mgkg-1 or ∞ (unclassified) based on the fixed LD₅₀ cut-off values. Final body weight of control rats (196.00 ± 3.06 g) was significantly (p < 0.05) higher than the initial body weight (184.30 ± 1.45 g) and weight gain in extract treated groups was not significant (p > 0.05). Packed cell volume, red blood cell count and haemoglobin concentrations in the rats (42.67 ± 1.33 %, 5.10 ± 0.20 x 10¹² L^-1 and 130.70 ± 2.96 gL^-1, respectively did not change significantly (p > 0.05). However,  the white blood cell count significantly increased from 7.50 ± 0.63 x 10⁹ to 11.63 ± 0.50 x 10⁹L^-1 while the lymphocyte count significantly increased from 5.81 ± 0.43 x 10⁹ to 9.99 ± 0.42 x 10⁹ L^-1 (p < 0.05) at the highest extract dose (5000 mgkg^-1) compared to their respective controls.

Conclusion: Adenium obesum might not be haematotoxic and is considered a safe medicinal plant  administered orally.