Drugs Osmotic Pumps

Wu T, Pao W, Chen J, Shang R. Formulation optimization technique based on artificial neural network in salbutamol sulfate osmotic pump tablets. Drug Dev Ind Pharm 2000 26 211-15. 

Wu et al. [46] used the approach of an artificial neural network and applied it to drug release from osmotic pump tablets based on several coating parameters. Gabrielsson et al. [47] applied several different multivariate methods for both screening and optimization applied to the general topic of tablet formulation they included principal component analysis and... 

As noted earlier, perhaps the key determinant of the overall release characteristics from an osmotic pump system is the solubility of the drug. If the solubility of the drug is too low, then the total dose that can be delivered is limited. If the solubility is too high, then the percent of the total dose that can be delivered at a zero-order rate can be relatively small. For example, as shown by Theeuwes [10], the fraction of the total dose (F) that can be delivered at a zero-order rate is given by... 

Numerous other examples of the use of solubility to control the delivery profile of drugs from the elementary osmotic pump can be found in the literature, especially the patent literature [35-40], These systems apply to drugs of moderate to high aqueous solubility where either the excipient or the salt form of the drug was used to control the drug solubility within the core formulation. 

Theeuwes, F. and Yum, S.I. (1976). Principles of the design and operation of generic osmotic pumps for the delivery of semisolid or liquid drug formulations. Ann. Biomed. Eng. 4 343-353. 

Pills can operate as osmotic "pumps" if they have miniscule laser-drilled holes in them. The pill coating is selective in that water from the body is allowed to enter to displace the drug at a constant rate. 

It is worthwhile to mention that (SB P-CD also makes controlled drug delivery more feasible for water-insoluble compound. It is well known that the release from controlled porosity osmotic pump tablets is limited due to its low aqueous solubility. However, Okimoto et al. (1999) successfully developed osmotic pump tablets for testosterone by using StjSBJD. Because each (SBEVm-P-CD molecule has an average of seven negative charges and seven sodium ions, it can act as... 

The rectal milieu is quite constant as its pH is about 7.5, and the temperature is usually 37°C. It is normally empty and the pressure varies between 0 and 50 cm. This makes this route suitable for the (controlled) delivery of drugs by applying adequate (controlled release) dosage forms such as osmotic pumps and hydrogels, since the classical suppositories are, in general, not the most suitable dosage form to achieve a reproducible rate and extent of drug absorption. 

Theeuwes and Higuchi1 applied the principle of osmotic pressure to a new generation of controlled drug delivery devices with many advantages over other existing controlled drug delivery systems. The first of these devices, the elementary osmotic pump, is considered a typical delivery system that operates on osmotic principles. 

The preceding equations apply to Push-Pull osmotic pumps that deliver water-soluble compounds. In that case, both drug and osmotic... 

The invention that positioned osmosis as a major driving force for controlled drug delivery was the elementary osmotic delivery system. ALZA has developed elementary osmotic delivery systems under the name OROS. A successful modification that overcame the disadvantages of the elementary osmotic pump was the Push-Pull osmotic drug delivery system. The following sections are devoted to the principal features of these systems. 

OROS Push-Pull system. After the introduction of commercial products based on EOP technology in the early 1980s, numerous attempts were made to apply the osmotic concept to a broader range of drugs. Since the elementary osmotic pump is limited to the delivery of relatively soluble drugs with solubilities greater than about 2 to 10 wt%, depending on dose, other modifications were necessary to expand the utility of the EOP... 

Okimoto, K., Ohike, A., Ibuki, R., et al. Design and evaluation of an osmotic pump tablet (OPT) for prednisolone, a poorly water soluble drug, using (SBE)7m-beta-CD. Pharm. Res. 15(10) 1562-1568, 1998. 

The principal application of these small osmotic pumps has been as implantable controlled release delivery systems in experimental studies on the effect of continuous administration of drugs. The devices are made with volumes of 0.2-2 mL. Figure 12.18 shows one such device being implanted in a laboratory rat. The delivery pattern obtained with the device is constant and independent of the site of implantation, as shown by the data in Figure 12.19. 

Figure 12.18 The Higuchi-Theeuwes osmotic pump has been widely used in drug delivery tests in laboratory animals. The device is small enough to be implanted under the skin of a rat and delivers up to 1000 iL of drug solution over a 3- to 4-day period [29,30]...

Figure 12.19 Drug delivery curves obtained with an implantable osmotic pump [30], Reprinted from F. Theeuwes and S.I. Yum, Principles of the Design and Operation of Generic Osmotic Pumps for the Delivery of Semisolid or Liquid Drug Formulations, Ann. Biomed. Eng. 4, 343, 1976, with permission of Biomedical Engineering Society...

---