Effect of sub-chronic cocaine and lidocaine exposure on the lymphoid tissues in neonatal rats

Illicit cocaine varies in purity and is often adulterated with local anesthetics such as lidocaine. Chronic cocaine exposure is associated with immunological modulation in humans and animal models. The effect of sub-chronic oral exposure to cocaine (COG) and lidocaine (LIDO) alone and in combination on the lymphoid organs was assessed in neonatal rats. Lewis rat pups were orally administered saline (SAL), COG, LIDO or both drugs in combination, 20 mg/kg each, from birth to day 21. Statistically significant (P < 0.05) decreases in lymphocyte and total leukocyte levels as well as decreases in spleen weight were observed in pups treated with COC alone. LIDO alone did not affect these parameters in comparison to SAL treated controls. Rats receiving COC and LIDO did not display a significant reduction in spleen weight or in the blood cell populations studied. However, rats treated with COC and LIDO in combination had significantly decreased serum immunoglobulin M(IgM) concentration. Quantitative plasma and tissue analyses ascertained the concentrations and tissue dispostion of each drug following oral administration. The results suggest that the effect of COC on the lymphoid tissues and white blood cell parameters is modified in the presence of LIDO in the developing rat.