Effects of JP789 on the Pharmacokinetics of Digoxin - Assignment Example

POTENTIAL EFFECTS OF JP789 ON THE PHARMACOKINETICS OF DIGOXIN By + Potential Effects of JP789 on the Pharmacokinetics of Digoxin P-gp, also known as ABCB1, or CD243, is a membrane transporter found in high concentration in the intestinal epithelium, blood brain barrier, liver, and kidney (Fenner et al., 2009). Along with cytochrome P450, CD243 limits the bioavailability of drugs by reducing their cellular uptake. For example, it inhibits the bioavailability of orally administered drugs by transporting them back into the intestinal lumen (Finch & Pillans, 2014). In humans, P-gp is found in abundance in the proximal renal tubules, the apical membrane of mucosal cells of the intestine, placental trophoblasts, the billiary membrane of hepatocytes, and capillary endothelial cells of the testis and brain. In these tissues, CD243 helps protect the tissue from cytotoxic effects of toxins. Further still, P-gp promotes the excretion of drugs into the bile ducts of the liver, excretion of drugs into urine, and excretion of drugs into the capillaries of the BBB (Schinkel et al., 1995; Horn & Philip, 2004). Different studies have been conducted in which various inhibitors of P-gp (MDR1) have been used to evaluate the bioavailability of drugs following the inhibition of MDR1. In one such study, the investigators used Dipyridamole to inhibit MDR1. The study hypothesized that inhibition of dipyridamole inhibition will result in increased bioavailability of digoxin. The study found out that dipyridamole increases the absorption of digoxin at the intestine and the plasma levels of digoxin were increased (Celine et al., 2003). In another study, the effect of MDR1 inhibition was measured on the effect of drug interaction between digoxin and quinidine. Quinidine enhances plasma concentration of digoxin by inhibiting MDR1. The co-administration of quinidine and digoxin resulted in an elevated concentration of digoxin and reduced excretion in urine (Fromm et al., 1999). Another study on mice indicated that absence of MDR 1 resulted in reduced excretion of digoxin (Funakoshi et al., 2003), dexamethasone, and Cyclosporin A (Schinkel et al., 1995). Rifampin is an inducer of CD243. A study conducted to determine the bioavailability of digoxin following the administration of rifampin revealed that the plasma concentration of digoxin dropped significantly. The drop has been accounted for by the understanding that rifampin induces the activity of MDR 1. JP 789 inhibits the action of MDR1 and therefore it can be hypothesized that during the interaction study, JP789 will result in an increase in the plasma concentration of digoxin and its reduced excretion in kidney and other organs. Digoxin in circulation exists in the bound and unbound form. About 25% of digoxin in circulation exists bound to albumin (Dasqupta, 2002). The unbound form of digoxin is the pharmacologically active component of digoxin in circulation. Digoxin has a narrow therapeutic window and the margin of error is very little. The difference between its toxic tissue concentration and the therapeutic concentration is small. Although there is variation between different individuals, the accepted therapeutic concentration is 0.5 to 2.0µg/l (Sharma, 2009). Drag/regiment DRAG DOSAGE ROUTE Digoxin 0.5ml/ q.i.d per OS JP789 TD / q.i.d per OS Justification, 0.5 ml digoxin per OS is the therapeutic dose of digoxin,in this study were going to use the therapeutic dose for two drags in order to obtain the maximal desired effect. The shall administer the drag per OS, administer drag per OS will make it easy to administer the drag to the study participant, once a day administer the drag will make it easier and minimize any errors that may occur with the study participant nd taking the drag more than once a day for example if the study participant was were to take the drag three times a day, a participant can forget to take drag during the study. Currently the prevalence of heart failure in UK is around1.2 million people, there is enough evidence that digoxin can treat heart failure. JP 789 is believed to increase the plasma concentration of digoxin. This study shall prove whether JP789 can increase the plasma concentration of digoxin (unbound digoxin). If JP789 can increase the plasma concentration of digoxin JP890 can be used in the treatment and management heart failure in UK. This study shall provide critical information as to whether JP789 can be used in the treatment and management of When the concentration of unbound digoxin exceeds therapeutic concentrations, toxic effects such as seizures, heart failure, cardiac disrthythmias, and death may occur. Different companies have developed ELISA based immunoassays for the measurement of the quantity and or concentration of unbound digoxin in circulation. After measuring the unbound form, the bound can be determined. A good example of an immunoassay used to measure the unbound digoxin in circulation is time resolved fluorometry using monoclonal and polyclonal antibodies. JP789 Drug interaction Study Synopsis Protocol This study shall hypothesize that co-administration of JP789 with digoxin will result in increased bioavailability of digoxin. The null hypothesis is that co-administration of JP789 with digoxin will not result in increased bioavailability of digoxin. The objective of this protocol is to determine whether the new drug will affect the plasma concentration of digoxin. To this end, the study will use ten healthy male volunteers who are aged between 25 and 35, and have a body weight of 84+- 9kg. In order to address the objective, it is necessary to use healthy individuals whose physiology is intact. Using patients will introduce an element of variability, and confounding factors because the medication they are using may alter effects of the drugs under study. The study has chosen males in the age group of 25 to35 because at this age, they have finished the maturation process associated with teenage. Teenagers are still growing and experience a vast array of hormonal influences. Using males in the study will reduce the element of variability that may be introduced into the study when women participate, because of their hormonal cycling (Fields, 2014). The study will obtain ethical approval before commencement. The study participants will fast the night before and will not consume caffeine and alcohol for the time that the study will be in progress. Caffeine increases urination while alcohol may cause complications of the heart such as cardiac arrhythmias, high blood pressure and cardiomyopathies (American Heart Association, 2014). The study volunteers will undergo an EGD (esophaogastroduodenoscopy) without sedation so as to prevent any drug interaction that may occur between the study drugs and sedatives. Biopsies of the small intestines will be obtained and preserved under formalin for immunohistochemistry, and frozen in liquid nitrogen for western blot. On the following day, the study participants will be divided into 2 groups. One group will receive one dose of JP789 per OS q.i.d together with 0.5mg of digoxin per OS q.i.d for 4 days. The other group, the control, received only the 0.5mg of digoxin per os q.i.d for 4 days. The study participants are not to eat any food 10 hours before the administration of digoxin, and 4 hours after administration of digoxin. Digoxin was co-administered with JP789 among members of the intervention group. This would allow time for the drug interactions to occur at the intestines without interference. Venous blood samples (5mililiter) will be collected before the administration of digoxin and 0.5, 1, 2, 5, 7, 10, 18, and 24 hours after the administration of digoxin. The blood samples will be centrifuged and the plasma will be stored at -20°C in order to prevent the samples from degenerating. Total urine will be collected over the period that the study will be in progress for all the study participants. An electrocardiogram machine will be used to monitor the heart activity of the participants because the drugs under study influence the activity of the heart. Automatic fluorescent polarization immunoassay (TDx; Abbot Laboratories, Illinois, USA) will be used to determine the concentration of digoxin in plasma and urine samples of the patients. The study shall measure the pharmacologically active component of digoxin, the unbound form. The limit set for the study for quantification will be 0.1ng/ml. For immunohistochemical staining, 2.5 micrometer thick paraffin sections will be prepared from the intestinal specimens. Modified ABC technique (Fritz et al., 1993; Chu et al., 1993) will be used to immunostain the CYP3A subfamily using polyclonal antibodies from the rabbit that have been raised against the human CYP3A subfamily (Guengrich et al., 1986). The primary and secondary antibodies will then be diluted at 1:200 and then treated with neuraminidase for 2 hours. Hydrogen peroxide together with diaminobenzidine will be used to stain all the samples. In this study, rabbit anti-mouse antibody will be used as the secondary antibodies. In order to detect the P-gp, monoclonal anti P-gp antibody from sigma chemicals Missouri USA was used. The alkaline phosphatase (APAAP) method was used to determine P-gp (Sternberger et al., 1970). In order to quantify the P-gp, a histoanalyzer will be used. Western blot technique will also be used to analyze the P-gp. The developed western blot films will be scanned using an ELscript400 densitometer and using the ZeroDscan software, the optical density of the P-gp will be determined. Pharmacokinetic calculations will also be conducted where the trapezoidal rule will be used to calculate the area AUC of digoxin concentration from 0 to 3 and from 0 to 24hrs. Dose per AUC will be used to determine the systemic clearance. Using the data, the times when the digoxin concentration will be at its peak and the concentration of digoxin at its peaks will also be determined. Terminal log linear data points will be used to estimate the half life of digoxin. For statistical analysis, the Mann-Whitney test will be used to compare the quantitative pharmacokinetic and immunohistochemistry parameters in the two groups of study participants. Changes in the levels of P-gp and time when digoxin concentration was maximum was tested wuing the Wilcoxon rank test. Spearman rank test will be used to determine the correlation between intestinal specimen P-gp and plasma AUC of digoxin. Like many studies that have been conducted before, the inhibition of induction of MDR1 or CD 243 will have direct impact on the plasma and urine concentrations of digoxin. When the activity of P-gp is inhibited, the plasma concentration of digoxin increases and the excretion in urine reduced. Also when the activity of P-gp is induced, the plasma concentration of digoxin reduces and its concentration in urine increases. JP789, a new drug, inhibits the activity of P-gp. 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Absence of the MDR1a P-glycoprotein in mice affects tissue distribution and pharmacokinetics of dexamethasone, digoxin, and cyclosporin A. Journal of Clinical Investigation, 96, 1698-1705. SHARMA, R., GUY, A., RUDENSKI, E., LAMERTON, E., & KAIRA, P. 2009. The limitations of routine total digoxin immunoassay in patients with advanced chronic kidney disease. QJM, 102: 747-752. STERNBERGER, LA, HARDY, PH, CUCULIS, JJ, & MEYER, HG. 1970. The unlabeled antibody enzyme method of immunohistochemistry. Preparation and properties of soluble antigen-antibody complex (horseradish peroxidase–antihorseradish peroxidase) and its use in identification of spirochaetes. J Histochem Cytochem,18, 315-334. Read More