Disclosed is a prolonged-release formulation that can be used with zolpidem or an addition salt thereof having a pH-dependent solubility, comprising a matricial excipient based on a hydrophilic polymer selected from hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose or carboxymethylcellulose, plant gums and derivatives thereof, alginic acid derivatives, and starch and derivatives thereof, the matricial excipient containing a given dose of zolpidem or an addition salt thereof, comprising one or more acidifying agents in the form of an acid salt of an organic acid wherein the acid salt of the acidifying agent is monopotassium tartrate, monosodium tartrate, monosodium citrate, bisodium citrate, and/or mixtures thereof. The disclosure further relates to formulations comprising a first immediate-release layer comprising zolpidem or an addition salt thereof whose solubility is pH-dependent, and one or more binders, the first layer optionally containing one or more other excipients； and a second prolonged-release layer, adjacent to the first layer, comprising zolpidem or an addition salt thereof whose solubility is pH-dependent, one or more acidifying agents in the form of an acid salt, and one or more matricial excipients, the second layer optionally containing one or more other excipients.
