Anthelmintic levamisole and tetramisole gel compositions

An aqueous composition comprising:

• 3% to 15% by weight of a pharmaceutically acceptable salt of the anthelmintic l-6-phenyl-2,3,5,6-tetrahydroimidazo-[2,1-b]thiazole or dl-6-phenyl-2,3,5,6-tetrahydroimidazo-[2,1-b]thiazole;
• 30% to 50% by weight of water;
• 1.5% by weight of citric acid;
• 1.0% by weight of trisodium citrate acid;
• 14% to 25% by weight of propylene glycol;
• and 20% to 30% by weight of the gellant .alpha.-hydro-.OMEGA.-hydroxy-poly(oxyethylene)poly(oxypropylene)poly(oxye thylene) block copolymer, average molecular weight 12,500, specific gravity 1.05;
• mp 56.degree. C., viscosity 3100 at 77.degree. C.;
• wherein said compositions are gels in the temperature range of from -20.degree. C. to +60.degree. C.;
• with the provisos that the water/gellant ratio is from 1.4/1.0 to 2.0/1.0;
• and that the components of said composition add up to a total of 100% by weight.

An aqueous, thermally reversible gel composition characterized by a sub-zero gelation temperature, comprising:

• 3% to 15% by weight of a pharmaceutically acceptable salt of the anthelmintic l-6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole or dl-6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole;
• 14% to 25% by weight of propylene glycol;
• an antimicrobially effective amount of benzyl alcohol;
• at least 30% by weight of water;
• at least 20% by weight of the gellant .alpha.-hydro-.OMEGA.-hydroxypoly(oxyethylene)poly(oxypropylene)poly(oxyet hylene) block copolymer which has an average molecular weight of 12,500 and a specific gravity of 1.05 and provided that the ratio of water to gellant is in the range of from 1.4/1.0 to 2.0/1.0;
• and a sufficient amount of a buffer to adjust the pH of the finished gel composition to between pH 3.0 and pH 3.5.

A method for the preparation of an aqueous thermally reversible composition, characterized by a subzero gelation temperature, comprising:

• dissolving 3% to 15% by weight of a pharmaceutically acceptable salt of the anthelmintic compound of formula:
• ##STR6## wherein X is hydrogen or --NH--R;
• R is C.sub.2 -C.sub.5 alkanoyl or benzoyl;
• or the optical isomers thereof;
• 1.5% by weight of citric acid and 1.0% by weight of trisodium citrate in 30% to 50% by weight of water;
• dissolving 0.5% by weight of benzyl alcohol in 14% to 25% by weight of propylene glycol;
• combining the two solutions and adding 0.01% to 0.03% by weight of C.I. Acid yellow No. 23;
• 0.001% to 0.02% by weight of an antifoaming agent comprising a mixture of dimethylpolysiloxanes of formula:
• ##STR7## silica gel wherein the calculated average value of m is 200-350, the mixture is a viscous liquid, d=0.965-0.970, n.sub.D.sup.25 about 1.404, viscosity about 60,000 centistokes;
• stirring and cooling the combined solution mixture from -20.degree. C. to -22.degree. C. and adding 20% to 30% by weight of the gellant .alpha.-hydro-.OMEGA.-hydroxy-poly(oxyethylene)poly(oxypropylene)poly(oxye thylene) block copolymer, average molecular weight 12,500;
• specific gravity 1.05;
• mp 56.degree. C., viscosity 3100 at 77.degree. C.;
• and stirring said mixture until a clear solution occurs;
• with the provisos that the water/gellant ratio is from 1.4/1.0 to 2.0/1.0;
• and that the components of said composition add up to a total of 100%.

A method for the preparation of an aqueous thermally reversible composition, characterized by a subzero gelation temperature, comprising:

• dissolving 3% to 15% by weight of a pharmaceutically acceptable salt of the anthelmintic l-6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]-thiazole, or dl-6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]-thiazole;
• 1.5% by weight of citric acid and 1.0% by weight of trisodium citrate in 30% to 50% by weight of water;
• dissolving 0.5% to 1.5% by weight of benzyl alcohol in 14% to 25% by weight of propylene glycol;
• combining the two solutions and adding 0.01% to 0.03% by weight of C.I. Acid yellow No. 23;
• 0.001% to 0.02% by weight of an antifoaming agent comprising a mixture of dimethylpolysiloxanes of formula ##STR8## silica gel wherein the calculated average value of m is 200-350, the mixture is a viscous liquid, d=0.965-0.970, n.sub.D.sup.25 about 1.404, viscosity about 60,000 centistokes;
• stirring and cooling the combined solution mixture from -20.degree. C. to -22.degree. C. and adding 20% to 30% by weight of the gellant .alpha.-hydro-.OMEGA.-hydroxy-poly(oxyethylene)poly(oxypropylene)poly(oxye thylene) block copolymer, average molecular weight 12,500, specific gravity 1.05;
• mp 56.degree. C., viscosity 3100 at 77.degree. C.;
• and stirring said mixture until a clear solution occurs;
• with the provisos that the water/gellant ratio is from 1.4/1.0 to 2.0/1.0;
• and that the components of said composition add up to a total of 100%.