A pharmaceutical composition comprising a polydeoxyribonucleotide of random sequence formula is disclosed, and P.sub.v, (dAp).sub.w, (dGp).sub.x, (dTp).sub.y, (dCp).sub.z wherein P.sub.v is 1-5 phosphoric radicals, (dAp).sub.w is 12-24 deoxyadenylic monomers, (dGp).sub.x is 10-20 deoxyguanylic monomers, (dTp).sub.y is 13-26 deoxythymidylic monomers, and (dCp).sub.z is 10-20 deoxycytidylic monomers; wherein the polydeoxyribonucleotide has: a homogenous anodic mobility in electrophoresis, an extinction coefficient E.sup.1%.sub.1 cm at 260.+-.1 nm=220.+-.10, an extinction coefficient E.sub.230 /E.sub.260 =0.45.+-.0.04, a molar extinction coefficient (referred to phosphorous), .epsilon.(P)=7750.+-.500, a rotary power �.alpha.!.sup.20.degree..sub.D =53.degree..+-.6, and a reversible hyperchromicity as percent in native DNA h=15.+-.5, in combination with a pharmaceutically acceptable carrier or diluent. A method of treating or preventing a diabetic neuropathy using the polydeoxyribonucleotide is also shown.