Methods and pharmaceutical compositions for inhibiting or decreasing transport of a drug by a transporter of multidrug resistance-associated protein comprising a compound of Formula (VI) ##STR00001##
wherein R.sub.1 and R.sub.2 are small peptides or modified peptides, are provided. The methods and compositions are useful in enhancing efficacy of drugs such as anti-inflammatory agents, neurological agents, thyroid agents, ocular agents, cancer chemotherapeutics, antibiotics, antimicrobials, antivirals and protease inhibitors to treat human immunodeficiency virus.

Methods and pharmaceutical compositions for inhibiting or decreasing transport of a drug by a transporter of multidrug resistance-associated protein comprising a compound of Formula (V): ##STR00001##
wherein R.sub.1 and R.sub.2 are small peptides or modified peptides, are provided. The methods and compositions are useful in enhancing efficacy of drugs such as anti-inflammatory agents, neurological agents, thyroid agents, ocular agents, cancer chemotherapeutics, antibiotics, antimicrobials, antivirals and protease inhibitors to treat human immunodeficiency virus.

The present invention provides a crystal of reduced glutathione having excellent powder properties and a method for producing the same. The present invention relates to a crystal of reduced glutathione, wherein the average crystal thickness is 10 m or more.

The invention provides a method of efficiently and stably producing -form crystal of reduced glutathione, and a preservation method thereof. According to the invention, development of -form crystal and/or transition to -form crystal of reduced glutathione are suppressed by the coexistence of at least one kind of compound selected from the group of aliphatic amino acid, sulfur-containing amino acid, aromatic amino acid, an analogous compound and dipeptide, as a habit modifier, during production and preservation of an aqueous solution or -form crystal of reduced glutathione.