Possible mechanism of adverse reaction following levodopa plus benserazide treatment

1 Rats treated for seven days with seryl-trihydroxybenzylhydrazine (benserazide), and inhibitor of peripheral aromatic L-amino acid decarboxylase (500 mg/kg, daily, i.p.) alone or in combination with L-DOPA methylester (500 mg/kg, daily, i.p.) for seven days showed a moderate but significant decrease of liver aldehyde dehydrogenase (ALDH), without accompanying change in alcohol dehydrogenase (ADH) activity, compared with saline-treated controls. 2 Administration of L-DOPA methylester (500 mg/kg, daily, i.p.) alone for seven days had little effect on liver ADH or ALDH. 3. The combined treatment might be conducive to the in vivo formation of L-DOPA-derived tetrahydroisoquinoline derivatives which might be implicated in L-DOPA produced adverse effects.