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Liposomal methylprednisolone in rats: dose-proportionality and chronic-dose pharmacokinetics/pharmacodynamics
1Department of Pharmaceutics, School of Pharmacy, State University of New York at Buffalo 14260, USA.
Purpose:
Methylprednisolone (MPL) encapsulated in liposomes (L-MPL) targets the immune system and enhances immunosuppressive activity of the steroid. We performed dose-dependent and chronic dose studies of L-MPL versus MPL.
Methods:
Male Lewis rats received 10 mg/kg i.v. bolus doses of L-MPL (Solu-Medrol). Plasma samples were obtained over an 8 day period and MPL concentrations were assayed by HPLC. Immunosuppressive effects were measured as inhibition of ex vivo splenocyte proliferation induced with PHA.
Results:
Drug concentrations declined in a similar manner over the first few hours following MPL or L-MPL. Free MPL was cleared from plasma by 6 hr, while the same dose of L-MPL resulted in persistence over an 8-day period. Dose-dependent changes in pharmacokinetic parameters were observed for both free and liposomal drug. Increasing the dose from 2 to 10 mg/kg led to increased clearance from 5.9 to 10.5 (MPL) and from 1.8 to 2.3 L/hr/kg (L-MPL). Blastogenesis was suppressed over 5 days with return to the baseline at day 8 (L-MPL); free MPL produced immunosuppression only over 10 hr. Multiple 2 mg/kg i.v. doses of L-MPL versus MPL twice a week produce plasma drug profiles similar to those obtained after single doses, indicating that neither free nor liposomal steroid accumulates in tissues. Liposomes without drug simultaneously administered with MPL caused partial prolongation of plasma steroid half-life (8.4 hr).
Conclusions:
These studies clarify factors causing prolonged drug persistence and immunosuppression with L-MPL. Nonlinear disposition, irregular pharmacokinetics, and secondary effects of the liposomes are complicating factors in use of L-MPL.
Insights
Liposomal methylprednisolone (L-MPL) offers prolonged immunosuppression compared to free MPL, persisting for 5 days versus 10 hours. This enhanced drug persistence is due to complex pharmacokinetic factors.
Area of Science:
- Pharmacology
- Immunology
- Drug Delivery Systems
Background:
- Methylprednisolone (MPL) is a steroid with immunosuppressive properties.
- Encapsulating MPL in liposomes (L-MPL) aims to enhance its targeted delivery and prolong its activity.
- Understanding the pharmacokinetics and pharmacodynamics of L-MPL is crucial for optimizing its therapeutic use.
Purpose of the Study:
- To compare the dose-dependent and chronic effects of liposomal methylprednisolone (L-MPL) versus free methylprednisolone (MPL).
- To investigate the pharmacokinetic profile and immunosuppressive duration of L-MPL in vivo.
- To elucidate factors contributing to the prolonged persistence and immunosuppression observed with L-MPL.
Main Methods:
- Male Lewis rats were administered intravenous bolus doses of L-MPL or MPL.
- Plasma concentrations of MPL were measured over 8 days using High-Performance Liquid Chromatography (HPLC).
- Immunosuppressive effects were assessed by measuring the inhibition of ex vivo splenocyte proliferation induced by phytohemagglutinin (PHA).
Main Results:
- Free MPL was cleared from plasma within 6 hours, while L-MPL persisted for 8 days.
- L-MPL suppressed splenocyte proliferation for 5 days, compared to only 10 hours for free MPL.
- Dose-dependent changes in clearance were observed for both MPL and L-MPL, with L-MPL showing nonlinear disposition.
Conclusions:
- Liposomal encapsulation significantly prolongs the persistence and immunosuppressive activity of methylprednisolone.
- Nonlinear disposition and secondary effects of liposomes complicate the pharmacokinetics of L-MPL.
- Further research is needed to fully understand and optimize the clinical application of L-MPL.