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LIPID FORMULATIONS FOR PARENTERAL ADMINISTRATION

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LIPOSOMES AS PHARMACEUTICAL DELIVERY VEHICLE – WHAT SCIENCE TELLS US

The advantages of liposome technology in pharmaceutical applications are being discovered by research teams all over the world. We present a broad selection of this research below. The numbers refer to the sources cited at the bottom of this page.

BIOLOGICAL AVAILABILITY

When an active drug substance is encapsulated in a liposome, it can be protected from rapid degradation and elimination in the body. The substance is therefore able to circulate inside the body for a longer period of time. This will increase the likelihood that the active substance will enter the target tissues and cells. Research has also shown that more than one substance can be loaded into a liposome to make the substances work synergistically [1].

ENHANCED DELIVERY

There are many different ways to administer a liposomal form of an active substance, for instance by intravenous infusion, local injection, inhalation but also by simple oral intake. While the administration of liposomal medicines into the bloodstream can be a very clear and direct way to target diseased sites in the body, oral administration is often preferable as a less invasive administration route. The disadvantage of the oral route is that the liposomes have to pass through the stomach and intestine, which form a relatively hostile environment affecting the stability of liposomal products. A great deal of research effort has been undertaken to engineer liposomes that pass through the stomach and intestine intact, showing that in some cases the biological availability of orally administered active substances can indeed be enhanced [1]. However, for pharmaceutical applications mostly parenteral administration routes are chosen. Parenteral administration of a liposomal formulation will alter pharmacokinetics of the drug substance. Moreover drug release times can be altered, delivery at the targeted disease site increased and toxic side effects diminished.

BETTER EFFICACY – LESS TOXICITY

Liposomes are typically composed of naturally derived ingredients. They are essentially non-toxic and biologically degradable. They have the unique ability to hold active substances – including drugs and supplements – both in their aqueous interior as well as their lipid bilayer. This makes liposomes attractive as drug delivery systems. Selective drug delivery at diseased sites in the body increases the local concentration of the drug improving its pharmacologic effect. It has also been demonstrated that the liposomal encapsulation of a drug can significantly reduce its toxicity by the tendency of liposomes to avoid healthy organs and protect these from exposure to the encapsulated drug [2,3,4].

 

PROTECTION

Studies reveal that liposomes – harnessing their ability to encapsulate and transport active drug substances – can increase the bioavailability and target delivery of these drug substances in the body. This effect has been attributed to:

  • liposomal protection of the active substance against enzymatic degradation by the body’s metabolism;
  • liposomes can address chemical and physical stability problems in formulations
  • liposome formulations can preventprecipitation/aggregation after injection of the drug
  • prolongation of the ‘residence time’ of a liposomal encapsulated active drug substance in the body and at the target site;
  • liposomal selective delivery in tumors and other disease sites
  • liposomal selective delivery at inflammatory sites
  • liposomal co-delivery of compounds to target cells

IMPROVED DRUG RELEASE TIME

Liposomal formulations allow modulation of the drug release time. During clinical development of a drug product, the pharmacokinetic behavior of the chosen drug substance may not suffice for the intended application and require more frequent dosing than desired. By designing the appropriate liposomal formulation, the drug release time can be optimized allowing less frequent dosing. Other advanced lipid formulations may also achieve slower release times.

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