Release of octopamine and alpha-methyloctopamine by L-dopa

Effect of L-dopa treatment on cerebral amino acid levels in rats after portocaval anastomosis

L-Dopa therapy has been suggested as effective in the reversal of hepatic coma both in humans and in animals. Beneficial effects have been reported also in chronic hepatic encephalopathy. There are many possible mechanisms through which L-dopa could ameliorate this pathological state. The present study was carried out to clarify whether the L-dopa effect could be mediated through an improvement of the brain neutral amino acid patterns, since it competes for the same transport carrier at the blood-brain barrier. A first group of rats was orally administered L-dopa (10 mg/100 g body weight daily) for 1 month following portocaval anastomosis. A second group was intraperitoneally injected (1.5 mg/100 g body weight daily) for 1 week, a month after portocaval shunt. Amino acid levels were determined in plasma and in four cerebral regions. No beneficial effects were observed clinically (in general condition, body weight, or hypertonic posture) in rats receiving L-dopa compared to controls. The large increase of tyrosine, phenylalanine, tryptophan, histidine, and glutamine that occurs in the cerebral tissue after portocaval shunt was also not affected by L-dopa administration. In conclusion, in this experimental condition we had no clinical improvement in shunted animals receiving L-dopa. Moreover, this compound did not seem to influence the pathological increase of aromatic amino acids in the brain, which is considered to play an important role in hepatic encephalopathy.

Preventing portal systemic encephalopathy in the patient with cirrhosis

Portal systemic encephalopathy is a serious complication of cirrhosis. It can be prevented if the patient avoids the contributing factors--ingestion of alcohol, inappropriate diet, infection, stress, hepatotoxic agents--and if other complications are treated promptly.

L-dopa in hepatic coma

The use of L-Dopa in hepatic coma has been the subject of numerous reports since 1970. The following represents our experience with a rather heterogenous group of patients treated at the Massachusetts General Hospital over the past 4 years. Thirty-five patients with severe liver disease, a mean age of 53 +/- 3.5 years, including nutritional cirrhosis with acute coma and acute hepatitis were treated. Four patients were judged grade III, 31 patients grade IV. All patients had previously been treated with protein restriction, orally administered non-absorbable antibiotics, fluid and electrolytes, and in some cases, steroids. L-Dopa was given orally in 21 patients, and as a retention enema in 14. Thirteen of the 35 patients did not respond to therapy. Seventeen responded, but did not survive, and 5 patients responded and survived. There was no difference between any of the groups as far as dosage of L-Dopa and clinical features. The one striking finding as the differences between groups was the time of initiation of L-Dopa therapy. In Group I, the survivors, therapy was started within 1.4 +/- 0.8 days after the onset of coma. In Group II, there was an initiation of therapy at 6.7 +/- 1.6 days, and in the non-responders 9.5 +/- 1.6 days. These differences are highly significant. The results suggest that coma may pass from a reversible to an irreversible stage, and that L-Dopa therapy initiated early in the course of hepatic coma, may be of some benefit.