Crystal suspensions of insulin derivatives, processes for their preparation and their use

A process for the preparation of a suspension of crystals of substantially uniform particle size and substantially uniform shape suitable for injection of at least one insulin derivative of the formula I ##STR5## in which R.sup.1 denotes H or H-Phe,

• R.sup.30 represents the radical of Ala, Thr or Ser and
• R.sup.31 represents a physiologically acceptable organic group of basic character of the formula X.sub.n -S which has up to 50 carbon atoms, in which n is 0, 1, 2 or 3
• X represents identical or different radicals of naturally occurring basic L-amino acids or of the corresponding D-amino acids or both and
• S denotes OH or a physiologically acceptable protective group which blocks the carboxyl group, but S being, if n is 0, a positively charged or protonatable basic radical and, if n is greater than 0, S can carry such a radical
• and which contains or does not contain a terminal carboxyl function or an ester or an amide thereof, with an isoelectric point between 5.8 and 8.5, which comprises carrying out the crystallization in an aqueous medium closes to the isoelectric point of the derivative in the presence of at least one phenol and of glycerol as an isotonicity agent.