Comparative Pharmacokinetics and Egg Residues of Amoxicillin, Single and in Combination with Bromhexine, in Laying Hens

The need for antibiotics in commercial laying hens is increasing owing to intensive farming systems. Amoxicillin trihydrate (AMX), an aminopenicillin β-lactam antibiotic, exerts broad bactericidal activity. However, its short half-life necessitates frequent administration to ensure efficacy, thus limiting its use. Herein, we investigated the effect of concurrent administration of bromhexine hydrochloride (BRM), a mucolytic agent, on AMX pharmacokinetics, performing a comparative pharmacokinetic analysis of AMX administration alone and in combination with BRM. AMX (50 mg/kg) was administered by oral gavage once daily for three days alone or in combination with 10 mg/kg BRM. Plasma and egg samples were collected to evaluate pharmacokinetic profiles and egg residues. The area under the curve and maximum plasma concentration values were significantly higher in the AMX + BRM group than the AMX only group. However, there were no significant differences in AMX half-life in the elimination phase (T_1/2), elimination rate constant (k_el), or apparent clearance (CL/F) values. In the egg residue study, the withdrawal period for AMX was 5 days in both groups, with no significant difference when using the maximum residue limit (MRL) of 10 μg/kg. The concentration of BRM in the eggs remained at 100 μg/kg up to the fourth day following drug administration. Conclusion: These results confirmed that BRM co-administration increased systemic exposure to AMX, with a negligible residual impact of amoxicillin in eggs.