Pharmacokinetics of metformin after enteral administration in insulin-resistant ponies.

The research investigates how the drug metformin behaves in the bodies of insulin-resistant ponies once orally or nasally consumed. The results indicate that the drug’s concentration, clearance, and average lifespan within the body are similar to those in humans, but less effective due to its low bioavailability in horses.

Research Methodology

• The study involved 8 insulin-resistant (IR) ponies. Metformin, with a dosage of 30 mg/kg, was provided to each pony via a nasogastric tube. This tube goes through the nose and into the stomach, permitting accurate and direct administration of medication.
• Blood samples were drawn at regular intervals over a 24-hour period to evaluate metformin concentration in plasma over time.
• The concentration of metformin in plasma was identified using a method called liquid chromatography-electrospray tandem mass spectroscopy, a widely accepted analytic method in pharmacokinetics studies.
• Pharmacokinetic variables were ascertained using a noncompartmental analysis. This is a more flexible approach for determining how a drug is absorbed, distributed, metabolized, and excreted in the body.
• Additionally, metformin was administered orally at lower doses (15 mg/kg, twice daily) to a subset of 4 ponies for an additional 20 days. Blood samples were collected every 2 days to understand the equilibrium concentration (Css) of metformin following a regular intake.

Research Findings

• The elimination half-life of metformin was approximately 11.7 hours. This refers to the time the body takes to eliminate half of the drug, crucial for determining the dosing interval.
• The peak plasma concentration was achieved roughly 54 mins after administration with a concentration of 748 ng/mL.
• The area under the curve, a measure of the exposure to the drug, was 355 microg.h/mL, and the apparent clearance rate was about 90.6 mL/min/kg. This rate indicates how quickly the drug is cleared from the body.
• The steady-state concentration (Css), achieved after regular doses over the 20-day period, was found to be 122 ng/mL.

Conclusions

• Although metformin is known to enhance insulin sensitivity without provoking insulin secretion, its bioavailability in ponies, or the proportion of the dose that enters the bloodstream and has an active effect, was found to be low.
• The measures such as half-life and clearance of metformin in ponies were comparable to those in humans. However, during long-term oral administration, the Css was lower than values associated with therapeutic efficacy in humans.
• The researchers concluded the apparent poor long-term effectiveness of metformin in ponies is likely due to low bioavailability rather than rapid elimination.