Pentoxifylline

Pharmaceutical

Pharmaceuticals -> Listed in ZINC15

Pharmaceuticals

Pharmaceuticals -> Used in Switzerland

Breast Feeding; Lactation; Hematologic Agents; Phosphodiesterase Inhibitors; Platelet Aggregation Inhibitors; Xanthines

FDA approved drugs -> Active ingredient

FDA approved drugs -> Active ingredient

Pharmaceuticals

Positive

2.07

2.7

Agilent XCT

Electrospray ionization

formic acid (5.3nM)

172.0 Ų [M+Na]+ [CCS Type: DT; Buffer gas: N2; Ionization: ESI+; Dataset: TOXCAST; Source Identifier: DTXSID7023437]

158.5 Ų [M+H]+ [CCS Type: TW; Method: calibrated with polyalanine and drug standards]

167.95 Ų [M+Na]+ [CCS Type: TW; Method: calibrated with polyalanine and drug standards]

This chemical does not meet GHS hazard criteria for 4.5% (3 of 67) of reports.

Warning

H302 (95.5%): Harmful if swallowed [Warning Acute toxicity, oral]

P264, P270, P301+P317, P330, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 67 reports by companies from 5 notifications to the ECHA C&L Inventory.

Chronic therapy with pentoxifylline has not been associated with elevations in serum enzyme levels, although the rigor with which liver test abnormalities were sought in patients taking the drug was not always clear. Despite its use for more than 3 decades, pentoxifylline has been linked to only rare and not completely convincing cases of clinically apparent liver injury. Nevertheless, adverse effects of hepatitis, jaundice, cholestasis and increased liver enzymes are listed in product labels for pentoxifylline. In reported cases, the time to onset was 3 to 4 weeks and the pattern of liver enzyme elevations was distinctly cholestatic (Case 1). Autoimmune and immunoallergic features were not present. The injury was self-limited and there have been no reports of acute liver failure, chronic hepatitis or vanishing bile duct syndrome associated with pentoxifylline therapy.

Drug Induced Liver Injury Rank (DILIrank 2.0)

Pentoxifylline

Ambiguous-DILI-concern

5

Adverse reactions

DOI:10.1016/j.drudis.2016.02.015

Pentoxifylline

Pharmaceutical

Smith, C.D. and Nowell, L.H., 2024. Health-Based Screening Levels for evaluating water-quality data (3rd ed.). DOI:10.5066/F71C1TWP

Pentoxifylline

28.0

118.3

The usual dosage of pentoxifylline in extended-release tablet form is one tablet (400 mg) three times a day with meals.

Data used to generate the benchmarks include the following: Lowest Daily Dose (LDD): 1200 mg/day, Lowest Therapeutic Dose (LTD): 15.0 mg/kg-day, and Screening Dose: 0.005 mg/kg-day.

19-Nov-19

C04AD03

C - Cardiovascular system

QC - Cardiovascular system

Pentoxifylline, a synthetic dimethylxanthine derivative structurally related to [theophylline] and [caffeine], exhibits hemorheological, anti-oxidative, and anti-inflammatory properties and is traditionally indicated in the treatment of peripheral arterial disease (PAD). In PAD patients with concurrent cerebrovascular and coronary artery diseases, pentoxifylline treatment has occasionally been associated with angina, arrhythmia, and hypotension. Concurrent use with [warfarin] should be associated with more frequent monitoring of prothrombin times. Also, patients with risk factors complicated by hemorrhages, such as retinal bleeding, peptic ulceration, and recent surgery, should be monitored periodically for bleeding signs.

Patients with peripheral arterial disease (PAD) may suffer from intermittent claudication, exertional leg pain that resolves upon rest, which is underscored by a complex etiology including vascular dysfunction (reduced limb perfusion, angiogenesis, and microcirculatory flow), systemic inflammation, and skeletal muscle dysfunction. Pentoxifylline (PTX), (3,7-dimethyl-1-(5-oxohexyl)-3,7-dihydro-1H-purine-2,6-dione) or 1-(5-oxohexyl)-3,7-­dimethylxanthine, is a methyl-xanthine derivative that acts to lower blood viscosity by increasing erythrocyte flexibility, reducing plasma fibrinogen, inhibiting neutrophil activation, and suppressing erythrocyte/platelet aggregation; it also has antioxidant and anti-inflammatory effects. Although the precise mechanism of action has yet to be elucidated, numerous studies have suggested several effects of PTX. The classical interpretation of PTX's broad effects is due to its ability to act, _in vitro_, as a non-specific cyclic-3',5'-phosphodiesterase (PDE) inhibitor at millimolar concentrations; specifically, it has been proposed that inhibition of PDE type III and IV isozymes leads to elevated cyclic adenosine monophosphate (cAMP) levels, which mediate diverse downstream effects. This view has been challenged, specifically by observing those plasma concentrations of PTX in routine clinical use are typically only around 1μM, far lower than those used to inhibit PDEs _in vitro_. Instead, several studies have suggested that PTX can modulate adenosine receptor function, specifically the Gα-coupled A2A receptor (A2AR). Whether PTX acts directly as an A2AR agonist is unclear, although it can clearly increase the response of A2AR to adenosine. A2AR activation activates adenylyl cyclase, which increases intracellular cAMP levels; this observation may explain PTX's ability to increase intracellular cAMP in a PDE-independent fashion. Elevated cAMP levels have numerous downstream effects. cAMP-mediated activation of protein kinase A (PKA) suppresses nuclear translocation of NF-κB, which suppresses transcription of pro-inflammatory cytokines such as tumour necrosis factor (TNF-α), interleukin-1 (IL-1), and IL-6 as well as TNF-induced molecules such as adhesion molecules (ICAM1 and VCAM1) and the C-reactive protein (CRP). PTX has also been shown to prevent the downstream phosphorylation of p38 MAPK and ERK, which are responsible for assembling the NADPH oxidase involved in the neutrophil oxidative burst. This effect is due to a PKA-independent decrease in Akt phosphorylation and a PKA-dependent decrease in phosphorylation of p38 MAPK and ERK. This transcriptional regulation at least partially explains the anti-inflammatory and anti-oxidative properties of PTX. Also, activated PKA can activate the cAMP response element-binding protein (CREB), which itself blocks SMAD-driven gene transcription, effectively disrupting transforming growth factor (TGF-β1) signalling. This results in lower levels of fibrinogenic molecules such as collagens, fibronectin, connective tissue growth factor, and alpha-smooth muscle actin. Hence, disruption of TGF-β1 signalling may explain the anti-fibrotic effects of PTX, including at least some of the decrease in blood viscosity. The picture is complicated by the observation that PTX metabolites M1, M4, and M5 have been shown to inhibit C5 Des Arg- and formyl-methionylleucylphenylalanine-induced superoxide production in neutrophils and M1 and M5 significantly contribute to PTX's observed hemorheological effects. Overall, PTX administration is associated with decreased pro-inflammatory molecules, an increase in anti-inflammatory molecules such as IL-10, and decreased production of fibrinogenic and cellular adhesion molecules.

Pentoxifylline (PTX) metabolism is incompletely understood. There are seven known metabolites (M1 through M7), although only M1, M4, and M5 are detected in plasma at appreciable levels, following the general pattern M5 > M1 > PTX > M4. As PTX apparent clearance is higher than hepatic blood flow and the AUC ratio of M1 to PTX is not appreciably different in cirrhotic patients, it is clear that erythrocytes are the main site of PTX-M1 interconversion. However, the reaction likely occurs in the liver as well. PTX is reduced in an NADPH-dependent manner by unknown an unidentified carbonyl reductase to form either [lisofylline] (the (R)-M1 enantiomer) or (S)-M1; the reaction is stereoselective, producing (S)-M1 exclusively in liver cytosol, 85% (S)-M1 in liver microsomes, and a ratio of 0.010-0.025 R:S-M1 after IV or oral dosing in humans. Although both (R)- and (S)-M1 can be oxidized back into PTX, (R)-M1 can also give rise to M2 and M3 in liver microsomes. _In vitro_ studies suggest that CYP1A2 is at least partly responsible for the conversion of [lisofylline] ((R)-M1) back into PTX. Unlike the reversible oxidation/reduction of PTX and its M1 metabolites, M4 and M5 are formed via irreversible oxidation of PTX in the liver. Studies in mice recapitulating the PTX-ciprofloxacin drug reaction suggest that CYP1A2 is responsible for the formation of M6 from PTX and of M7 from M1, both through de-methylation at position 7. In general, metabolites M2, M3, and M6 are formed at very low levels in mammals.

Pentoxifylline is a known human metabolite of lisofylline.

SD6QCT3TSU

PENTOXIFYLLINE

Established Pharmacologic Class [EPC] - Blood Viscosity Reducer

Physiologic Effects [PE] - Hematologic Activity Alteration

Pentoxifylline is a Blood Viscosity Reducer. The physiologic effect of pentoxifylline is by means of Hematologic Activity Alteration.

PENTOXIFYLLINE

Compounds which inhibit or antagonize the biosynthesis or actions of phosphodiesterases.

Drugs or agents which antagonize or impair any mechanism leading to blood platelet aggregation, whether during the phases of activation and shape change or following the dense-granule release reaction and stimulation of the prostaglandin-thromboxane system.

Drugs used to protect against ionizing radiation. They are usually of interest for use in radiation therapy but have been considered for other purposes, e.g. military.

Drugs used to cause dilation of the blood vessels.

Substances that eliminate free radicals. Among other effects, they protect PANCREATIC ISLETS against damage by CYTOKINES and prevent myocardial and pulmonary REPERFUSION INJURY.

Oral pentoxifylline (PTX) is almost completely absorbed but has low bioavailability of 20-30% due to extensive first-pass metabolism; three of the seven known metabolites, M1, M4, and M5 are present in plasma and appear soon after dosing. Single oral doses of 100, 200, and 400 mg of pentoxifylline in healthy males produced a mean tmax of 0.29-0.41 h, a mean Cmax of 272-1607 ng/mL, and a mean AUC0-∞ of 193-1229 ng\*h/mL; corresponding ranges for metabolites 1, 4, and 5 were 0.72-1.15, 114-2753, and 189-7057. Single administration of a 400 mg extended-release tablet resulted in a heightened tmax of 2.08 ± 1.16 h, lowered Cmax of 55.33 ± 22.04 ng/mL, and a comparable AUC0-t of 516 ± 165 ng\*h/mL; all these parameters were increased in cirrhotic patients. Smoking was associated with a decrease in the Cmax and AUCsteady-state of metabolite M1 but did not dramatically affect the pharmacokinetic parameters of pentoxifylline or other measured metabolites. Renal impairment increases the mean Cmax, AUC, and ratio to parent compound AUC of metabolites M4 and M5, but has no significant effect on PTX or M1 pharmacokinetics. Finally, similar to cirrhotic patients, the Cmax and tmax of PTX and its metabolites are increased in patients with varying degrees of chronic heart failure. Overall, metabolites M1 and M5 exhibit plasma concentrations roughly five and eight times greater than PTX, respectively. PTX and M1 pharmacokinetics are approximately dose-dependent, while those of M5 are not. Food intake before PTX ingestion delays time to peak plasma concentrations but not overall absorption. Extended-release forms of PTX extend the tmax to between two and four hours but also serves to ameliorate peaks and troughs in plasma concentration over time.

Pentoxifylline is eliminated almost entirely in the urine and predominantly as M5, which accounts for between 57 and 65 percent of the administered dose. Smaller amounts of M4 are recovered, while M1 and the parent compound account for less than 1% of the recovered dose. The fecal route accounts for less than 4% of the administered dose.

Pentoxifylline has a volume of distribution of 4.15 ± 0.85 following a single intravenous 100 mg dose in healthy subjects.

Pentoxifylline given as a single 100 mg intravenous infusion has a clearance of 3.62 ± 0.75 L/h/kg in healthy subjects, which decreased to 1.44 ± 0.46 L/h/kg in cirrhotic patients. In another study, the apparent clearance of either 300 or 600 mg of pentoxifylline given intravenously (median and range) was 4.2 (2.8-6.3) and 4.1 (2.3-4.6) L/min, respectively. It is important to note that, due to the reversible extra-hepatic metabolism of the parent compound and metabolite 1, the true clearance of pentoxifylline may be even higher than the measured values.