The present disclosure provides methods for treating hepatic encephalopathy (HE) and for optimizing and adjusting nitrogen scavenging drug dosage for subjects with HE, comprising administering a nitrogen scavenging drug at a dosage sufficient to maintain a fasting blood ammonia level at or below a specified threshold level which is 1.5 times the upper limit of normal for blood ammonia. The nitrogen scavenging drug administered in the method is a phenylacetic acid prodrug selected from HPN-100, PBA, NaPBA, sodium benzoate, or any combination thereof (i.e. any combination of two or more of HPN-100, PBA, NaPBA).
