By S. Tukash. Belmont University.
Pores and channels produced by extensive polymer degradation are visualized in the micrograph cheap lozol 1.5 mg overnight delivery blood pressure ranges pregnancy. The release rate is determined by the polymer composition and molecular weight (Table 4 2.5 mg lozol with amex pulmonary hypertension 70 mmhg. The Lupron Depot microspheres are indicated for the treatment of male patients with prostate cancer and female patients suffering from endometriosis and anemia due to fibroids. Just prior to intramuscular injection, the diluent is withdrawn by a syringe and injected into the single-dose vial to homogeneously disperse the microspheres. An initial burst release of leuprolide from the microsphere depot occurs in vivo, followed by quasi-linear release for the rest of the time period. The efficacy of leuprolide depot formulations was found to be the same as the efficacy achieved with daily subcutaneous injections of 1 mg leuprolide formulation. Polymer degradation occurs via hydrolysis, the biscarboxyphenoxypropane monomer is excreted in the urine and the sebacic acid monomer is metabolized by the liver and is expired as carbon dioxide via the lung (Figure 4. Sebacic acid-rich copolymers display much faster degradation rates than biscarboxyphenoxy propane-rich copolymers. Changes in the ratio of the monomers are reported to provide various degradation rates ranging from 1 day to 3 years. To fabricate the implant, the polyanhydride and the drug moiety are dissolved in dichloromethane. The solution is spray dried to produce microspherical powders in which the drug is homogeneously dispersed. The powders are then compressed into a disk-shaped wafer, approximately 14 mm in diameter and 1 mm thick. Up to eight Gliadel wafers are implanted in the cavity created when a neurosurgeon removes the brain tumor. The wafers gradually degrade in the cavity and allows the delivery of high, localized doses of the anticancer agent for a long period, thereby minimizing systemic side-effects. The thin- disk type morphology of the wafer confers a high surface-to-volume ratio on the implant, so that the total surface area of the implant is kept almost constant over the time of polymer degradation, which facilitates a constant release of carmustine with time. This results in polymer degradation proceeding purely by surface erosion, which results in zero-order drug release from disk-shaped devices. Degradable block copolymers with polyethylene glycol, diglycolide, substituted caprolactones and l-valerolactone can also be synthesized.
Potential alternative portals of drug entry to the systemic circulation include the buccal purchase 2.5 mg lozol mastercard heart attack high bride in a brothel, sublingual cheap lozol 1.5 mg on-line blood pressure medication how long to take effect, nasal, pulmonary and vaginal routes. These routes are also being studied for the local delivery of drugs directly to the site of action, thereby reducing the dose needed to produce a pharmacological effect and also possibly minimizing systemic side-effects. Drug delivery technology is becoming increasingly sophisticated and current approaches take into account such factors as the influence of pharmacokinetic processes on drug efficacy, as well as the importance of drug timing and of drug targeting to the site of action. Emerging technologies are addressing a variety of issues, including bio-responsive drug release and the delivery of nucleic acid therapeutic entities. This book is concerned with the various routes of delivery under investigation, and these new and 3 emerging delivery technologies. However, a full appreciation of these concerns cannot be gained without first understanding: • the concept of bioavailability; • the process of drug absorption; • the pharmacokinetic processes; • the importance of timing for optimal drug therapy; • delivery considerations for the “new biotherapeutics”; • the limitations of conventional therapy. This chapter provides an overview of these considerations and highlights the necessity for advanced drug delivery systems, in order to optimize drug efficacy. In terms of drug efficacy, the bioavailability of a drug is almost as important as the potency of the active agent itself. Measuring a drug’s bioavailability thus involves measuring the rate and extent of drug absorption. This is ideally measured in terms of the clinical response of a patient; however, only a minority of clinical responses, such as blood pressure, can provide accurate quantitative data for analysis. A further method of assessment is the measurement of the drug concentration at the site of action; however, this cannot be achieved practically. For clinical purposes, it is generally accepted that a dynamic equilibrium exists between the concentration of drug at the site of action (C ) and the concentration of drug in blood plasma (C ). Thus Cs p p is generally used as an indirect indicator of the concentration of drug at its site of action and the most# commonly used method of assessing the bioavailability of a drug involves the construction of a Cp versus “Time” curve (Cp vs T curve). A typical Cp vs T curve following the administration of an oral tablet is given in Figure 1. At zero time (when the drug is first administered), the concentration of drug in the plasma is zero.
10 of 10 - Review by S. Tukash
Votes: 316 votes
Total customer reviews: 316