Disclosed is the use of a pharmaceutical composition comprising: eicosapentaenoic acid (“EPA”), in a weight percent amount of 50% to 60% docosahexaenoic acid (“DHA”) in a weight percent amount of 17% to 23% docosapentaenoic acid (n-3) (“DPA”) in a weight percent amount of 1% to 8% wherein at least 90% by weight of the polyunsaturated acid in the composition is present in the free acid form, in the manufacture of a medicament for the treatment of severe hypertriglyceridemia, wherein the treatment comprises: orally administering the to a patient having pre-treatment serum or plasma triglyceride levels ≥500 mg/dL, in an amount and for a duration effective to reduce serum or plasma triglycerides below pre-treatment levels. Also disclosed is the use of a pharmaceutical composition comprising: EPA, substantially in free acid form, in an amount of 55.1% (m/m) to 58.4% (m/m) DHA, substantially in free acid form, in an amount of 17.7% (m/m) to 22.2% (m/m) and DPA, substantially in free acid form, in an amount of 2.1% (m/m) to 8.5% (m/m) in the manufacture of a medicament for use in the treatment of a patient with elevated pretreatment serum or plasma triglycerides, wherein the treatment comprises: administering the medicament in an amount and for a duration effective to reduce arachidonic acid (AA) concentration in plasma by at least about 5%. Further disclosed is a method of making a pharmaceutical composition of polyunsaturated fatty acids in free acid form, the method comprising: (a) subjecting an intermediate feedstock of transesterified fish oil comprising the ethyl esters of EPA, in an amount of at least about 44% (a/a), DHA, in an amount of at least about 14% (a/a), and DPA, in an amount of at least about 1% (a/a), to a step of urea inclusion complexation (b) removing the resulting urea complexes and (c) hydrolyzing the uncomplexed PUFA esters to free fatty acids wherein the amount of urea used for complexation is calculated according to formula I(a), or according to
