Pentoxifylline
Pentoxifylline. Methylxanthine — increases red blood cell flexibility, decreases blood viscosity, mild antiplatelet effect. Used for… Oral half-life 1.6 h.
Methylxanthine — increases red blood cell flexibility, decreases blood viscosity, mild antiplatelet effect. Used for intermittent claudication symptoms (modest effect) and cutaneous ulcers (off-label for vasculitis).
PK: MY EXTENDED-RELEASE PRIOR IS REFUTED, AND FOR AN INSTRUCTIVE REASON. I expected the nifedipine defect — modified-release values under an immediate-release label — but EVERY candidate source used an extended-release product BECAUSE THAT IS THE ONLY MARKETED ORAL FORM. There is no immediate-release label to mismatch, this record dose block is the standard extended-release regimen, and its absorption rate is slower than its elimination rate, which correctly encodes flip-flop for a release-limited product. CLASS 6 IS ALSO ACQUITTED, verbatim: after a 200 mg INTRAVENOUS dose, "plasma levels declined in a biphasic manner, with a terminal t1/2 of 1.63 +/- 0.8 hr. Plasma clearance was 1333 +/- 481 ml/min and the volume of distribution was 168 +/- 82.3 l". The stored volume was that figure rounded and its pairing with F was correct all along. The real defects are smaller: F 0.20 is the LOW ENDPOINT of "bioavailability averaged 20% to 30%", where a stated mean exists elsewhere at 0.33, and the half-life was verbatim nowhere. A CLASS-13 FLAG IS RAISED AND DISMISSED: the implied absolute clearance exceeds hepatic blood flow, which would normally be impossible, but its own literature explains it — "suggesting an extrahepatic metabolism". The active metabolite runs higher than the parent and is unmodelled.
Pharmacokinetics
- Oral — t½ 1.6 h · F 33% · Vd 168 L
Sources: PMID:10478991, PMID:3965236, PMID:2178853