Pharmacokinetics

From Diabetes in Pets

Pharmacokinetics (abbreviated as PK in medical reading material) is basically the study of how a drug travels through the body. It's a "road map", if you will, of the "trip" drugs take through one's system^[1].

By measuring things like the plasma concentration of the drug over a given time period, measuring them in both the same and in different subjects, many "maps" are created. Studying them provides a picture of how a given drug behaves in most who use or take it. Things like the life or halflife of a drug in the system, onset, peak, absorption, and duration all come from pharmacokinetic measurements^[2]. It's pharmacokinetics which allows a doctor to know how Drug X at Y mg dosage will work in a patient--when the drug begins working, when it works hardest, or peaks, and when the drug wanes and is leaving the system^[3][4]. This knowledge is why you are sometimes told to take medications more than once a day.

We tend to focus more on the pharmacokinetics of insulins^[5][6][7], dealing with diabetes, but all drugs have pharmacokinetic profiles.

[edit] Insulin pharmacokinetics

Pharmacokinetics of Insulin Preparations[8]

Insulin Preparations

Onset (hr)

Peak (hr)

Duration (hr)

Rapid-Acting

R/Neutral

0.5 to 1

2.5 to 5

8 to 12

Lispro

0.25 to 0.5

0.5 to 1.5

2 to 5

Aspart

0.17 to 0.33

1 to 3

3 to 5

Glulisine

0.17 to 0.33

1 to 3

3 to 5

Intermediate-Acting

NPH Isophane

1 to 1.5

6 to 14

16 to 24

Lente[9]

1 to 3

6 to 14

20+

70/30-30/70

0.5 to 1

2 to 12

24

50/50

0.5 to 1

2 to 12

24

Novolog 70/30 Mix

0.25

1 to 3

24

Humalog 75/25 Mix

0.25

0.5 to 1.5

24

Long-Acting

Ultralente[10]

6

14 to 18

18 to 24

PZI[11]

4 to 6

14 to 18

24 to 36

Glargine

1.1

N/A

24

Detemir

0.8 to 2

N/A

up to 24

These are human activity profiles.

[edit] Further Reading

• Pharmacokinetic Concepts--WSAVA 2002

[edit] References

1. ↑ Merck Veterinary Manual-Disposition & Fate of Drugs
2. ↑ Merck Veterinary Manual-Drug Concentration in Blood
3. ↑ Merck Veterinary Manual-Pharmacokinetics-Overview
4. ↑ Merck Veterinary Manual-Drug Clearance-Elimination
5. ↑ Essentials of Insulin Pharmacokinetics-Wiener Klinische Wochenschrift--English Translation--1988
6. ↑ Insulin Pharmacokinetics-Diabetes Care-1984
7. ↑ Type I Diabetes and Insulin Therapy-Nursing Clinics of North America-Hirsch-Farkas-Hirsch 1993
8. ↑ Pharmacy Times-Guide to Insulin Preparations
9. ↑ Endotext.com-Insulin Pharmacology
10. ↑ Endotext.com-Insulin Pharmacology
11. ↑ NetDoctor-UK Hypurin Protamine Zinc