Evaluating Predictive Methods & Product Performance in Healthy Adults for Pediatric Patients, A Case Study: Furosemide

Poorly absorbed medications such as furosemide are common and recent experiments suggest that improvement in absorption can occur if these types of medications are consumed with liquids such as milk. The purpose of this study is to evaluate the absorption of furosemide in normal adults when taken with bottled water, milk (Parmalat™ Whole Milk), baby formula (Similac Pro-Advance™), or Ensure Plus™. These results will be used to make models that predict how these liquids will affect drug absorption in children, potentially providing ways to improve medication absorption in children.

Low solubility drugs are common in the pharmacopeia and it has been estimated that more than 40% of new chemical entities developed by the pharmaceutical industry are practically insoluble in water. Exploratory in vitro studies by the CDER have recently demonstrated that the solubility, and thus potentially the bioavailability, of poorly soluble drugs may be highly enhanced when administered with milk (Parmalat™ Whole Milk) or baby formula (Similac Pro-Advance™).

While the reasons for variable bioavailability of furosemide are not well characterized, the effect of gastric pH, food and dosing liquids are commonly observed on the absorption of BCS Class IV drugs. Absorption variability is much greater in children due to developmental changes in factors such as gastric fluid, blood flow to the intestine, bile acid composition/secretion, intestinal surface area and drug metabolizing enzyme and transporter abundance. Therefore, it is critical to determine the physio-chemical physiological interactions for furosemide that can explain inter-subject and inter-dosing variability. An integrated in vitro, in silico and in vivo pharmacology approach to study the effect of dosing liquids on PK and PD of furosemide is novel. Quantitative understanding of factors affecting furosemide absorption will first be evaluated using in vitro tests such as solubility, dissolution and protein binding with the dosing liquids. The physiochemical information relevant to drug absorption and elimination will be curated from the literature to build the PBPK model. Such in vitro- in vivo extrapolation (IVIVE) linked PBPK modeling approach is crucial to better characterize furosemide's variable bioavailability. Another novel aspect of this study is that we will include renal metabolism of furosemide in the PBPK modeling. While plasma concentration will be critical in determining rate and extent of furosemide absorption, the renal elimination is the primary contributor to the PD response of furosemide as delivery of drug to the luminal surface of the renal tubule is required. PBPK modeling allows extrapolation of model to special population. For example, once the model is optimized and validated to predict effect of dosing liquids on adult PK of furosemide from in vitro data, this approach can be further extrapolated to children using pediatric gut physiological parameters. This novel approach will allow prediction of furosemide PK and PD in children without conducting a clinical study in this difficult to study population.

Eligibility Criteria:
Inclusion Criteria:

* Age 18-40
* 4 females and 4 males will be recruited
* Free from known significant chronic medical illness (i.e., hypertension, diabetes, atherosclerosis, chronic kidney disease, liver disease, lupus, taking medications with known interactions with furosemide, a history of syncope/falls, or any acute illness, such as influenza, gastroenteritis, dehydration, electrolyte imbalance, or thrombosis risks).
* Systolic Blood Pressure ≥90 mmHg at Screening Visit

Exclusion Criteria:

* Inability to read English or give informed consent
* Recent hospitalization within 6 months
* Pregnant or lactating
* Allergy or intolerance to furosemide
* Allergy or intolerance to milk, milk products or soy
* Inability to return for 4 consecutive weekly overnight visits at the study site
* Female subjects with low, or borderline low blood pressure, will be evaluated carefully prior to enrollment, to ensure the safety of all subjects involved in the research study.