(pen tox i' fi leen)
P : Contraindicated in pregnancy
L : Contraindicated in lactation
|| See TERMINOLOGY & ABBREVIATIONS ||
|Indication(s) & Dosage||Pentoxifylline is indicated for the treatment of patients with intermittent claudication on the basis of chronic occlusive arterial disease of the limbs. Pentoxifylline can improve function and symptoms but is not intended to replace more definitive therapy, such as surgical bypass, or removal of arterial obstructions when treating peripheral vascular disease.
The usual dosage of Pentoxifylline in extended-release tablet form is one tablet (400 mg) three times a day with meals.
While the effect of Pentoxifylline may be seen within 2 to 4 weeks, it is recommended that treatment be continued for at least 8 weeks. Efficacy has been demonstrated in double-blind clinical studies of 6 months duration.
Digestive and central nervous system side effects are dose related. If patients develop these effects it is recommended that the dosage be lowered to one tablet twice a day (800 mg/day). If side effects persist at this lower dosage, the administration of Pentoxifylline should be discontinued.
|Overdose||Overdosage with Pentoxifylline has been reported in pediatric patients and adults. Symptoms appear to be dose related. A report from a poison control center on 44 patients taking overdoses of enteric-coated pentoxifylline tablets noted that symptoms usually occurred 4â€“5 hours after ingestion and lasted about 12 hours. The highest amount ingested was 80 mg/kg; flushing, hypotension, convulsions, somnolence, loss of consciousness, fever, and agitation occurred. All patients recovered. In addition to symptomatic treatment and gastric lavage, special attention must be given to supporting respiration, maintaining systemic blood pressure, and controlling convulsions. Activated charcoal has been used to absorb pentoxifylline in patients who have overdosed.|
|Contraindications||Pentoxifylline should not be used in patients with recent cerebral and/or retinal hemorrhage or in patients who have previously exhibited intolerance to this product or methylxanthines such as caffeine, theophylline, and theobromine.|
At the first sign of anaphylactic/anaphylactoid reaction, Pentoxifylline must be discontinued.
Patients with chronic occlusive arterial disease of the limbs frequently show other manifestations of arteriosclerotic disease. Pentoxifylline has been used safely for treatment of peripheral arterial disease in patients with concurrent coronary artery and cerebrovascular diseases, but there have been occasional reports of angina, hypotension, and arrhythmia. Controlled trials do not show that Pentoxifylline causes such adverse effects more often than placebo, but, as it is a methylxanthine derivative, it is possible some individuals will experience such responses. Patients on Warfarin should have more frequent monitoring of prothrombin times, while patients with other risk factors complicated by hemorrhage (e.g., recent surgery, peptic ulceration, cerebral and/or retinal bleeding) should have periodic examinations for bleeding including, hematocrit and/or hemoglobin.
Carcinogenesis, Mutagenesis and Impairment of Fertility
Long-term studies of the carcinogenic potential of pentoxifylline were conducted in mice and rats by dietary administration of the drug at doses up to 450 mg/kg (approximately 19 times the maximum recommended human daily dose (MRHD) in both species when based on body weight; 1.5 times the MRHD in the mouse and 3.3 times the MRHD in the rat when based on body surface area). In mice, the drug was administered for 18 months, whereas in rats, the drug was administered for 18 months followed by an additional 6 months without drug exposure. In the rat study, there was a statistically significant increase in benign mammary fibroadenomas in females of the 450 mg/kg group. The relevance of this finding to human use is uncertain. Pentoxifylline was devoid of mutagenic activity in various strains of Salmonella (Ames test) and in cultured mammalian cells (unscheduled DNA synthesis test) when tested in the presence and absence of metabolic activation. It was also negative in the in vivo mouse micronucleus test.
|Adverse Drug Reaction(s)||Nausea, vomiting, dizziness, headache, flushing; angina, palpitations; occasional cardiac arrhythmias; hepatitis, jaundice; blood dyscrasias reported; agitation; sleep disturbances; hypotension; thrombocytopenia; intrahepatic cholestasis.
Potentially Fatal: Fatal haemorrhage (cerebral and GI tract); anaphylactoid reaction.
Although a causal relationship has not been established, there have been reports of bleeding and/or prolonged prothrombin time in patients treated with Pentoxifylline with and without anticoagulants or platelet aggregation inhibitors. Patients on Warfarin should have more frequent monitoring of prothrombin times, while patients with other risk factors complicated by hemorrhage (e.g., recent surgery, peptic ulceration) should have periodic examinations for bleeding including hematocrit and/or hemoglobin.
Concomitant administration of Pentoxifylline and theophylline-containing drugs leads to increased theophylline levels and theophylline toxicity in some individuals. Such patients should be closely monitored for signs of toxicity and have their theophylline dosage adjusted as necessary.
Pentoxifylline has been used concurrently with beta blockers, digitalis, diuretics, antidiabetic agents, and antiarrhythmics, without observed problems. Small decreases in blood pressure have been observed in some patients treated with Pentoxifylline plus nifedipine or captopril; periodic systemic blood pressure monitoring is recommended for patients receiving concomitant antihypertensive therapy. If indicated, dosage of the antihypertensive agents should be reduced.
Postmarketing cases of increased anticoagulant activity have been reported in patients concomitantly treated with pentoxifylline and vitamin K antagonists. Monitoring of anticoagulant activity in these patients is recommended when pentoxifylline is introduced or the dose is changed.
|Food Interaction||Food: May reduce rate but not extent of absorption; administer with meals to minimise GI effects.|
|Lab Interference||False-positive theophylline levels.|
|Pregnancy Category (FDA) and use in Specific Population||
Pregnancy Category C.Teratogenicity studies have been performed in rats and rabbits using oral doses up to 576 and 264 mg/kg, respectively. On a weight basis, these doses are 24 and 11 times the maximum recommended human daily dose (MRHD); on a body-surface-area basis, they are 4.2 and 3.5 times the MRHD. No evidence of fetal malformation was observed. Increased resorption was seen in rats of the 576 mg/kg group. There are no adequate and well controlled studies in pregnant women. Pentoxifylline should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Pentoxifylline and its metabolites are excreted in human milk. Because of the potential for tumorigenicity shown for pentoxifylline in rats, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness in pediatric patients have not been established.
Clinical studies of Pentoxifylline did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
The active metabolite is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.
|Storage||Oral: Store at 15-30 Â°C.|
Mode of Action
Pentoxifylline and its metabolites improve the flow properties of blood by decreasing its viscosity. In patients with chronic peripheral arterial disease, this increases blood flow to the affected microcirculation and enhances tissue oxygenation. The precise mode of action of pentoxifylline and the sequence of events leading to clinical improvement are still to be defined. Pentoxifylline administration has been shown to produce dose-related hemorrheologic effects, lowering blood viscosity, and improving erythrocyte flexibility. Leukocyte properties of hemorrheologic importance have been modified in animal and in vitro human studies. Pentoxifylline has been shown to increase leukocyte deformability and to inhibit neutrophil adhesion and activation. Tissue oxygen levels have been shown to be significantly increased by therapeutic doses of pentoxifylline in patients with peripheral arterial disease.
Pharmacokinetics and Metabolism
After oral administration in aqueous solution pentoxifylline is almost completely absorbed. It undergoes a first-pass effect and the various metabolites appear in plasma very soon after dosing. Peak plasma levels of the parent compound and its metabolites are reached within 1 hour. The major metabolites are Metabolite l (1-[5-hydroxyhexyl]-3,7-dimethylxanthine) and Metabolite V (1-[3-carboxypropyl]-3,7-dimethylxanthine), and plasma levels of these metabolites are 5 and 8 times greater, respectively, than pentoxifylline.
Following oral administration of aqueous solutions containing 100 to 400 mg of pentoxifylline, the pharmacokinetics of the parent compound and Metabolite l are dose-related and not proportional (non-linear), with half-life and area under the blood-level time curve (AUC) increasing with dose. The elimination kinetics of Metabolite V are not dose-dependent. The apparent plasma half-life of pentoxifylline varies from 0.4 to 0.8 hours and the apparent plasma half-lives of its metabolites vary from 1 to 1.6 hours. There is no evidence of accumulation or enzyme induction (Cytochrome P450) following multiple oral doses.
Excretion is almost totally urinary; the main biotransformation product is Metabolite V. Essentially no parent drug is found in the urine. Despite large variations in plasma levels of parent compound and its metabolites, the urinary recovery of Metabolite V is consistent and shows dose proportionality. Less than 4% of the administered dose is recovered in feces. Food intake shortly before dosing delays absorption of an immediate-release dosage form but does not affect total absorption. The pharmacokinetics and metabolism of Pentoxifylline have not been studied in patients with renal and/or hepatic dysfunction. The pentoxifylline AUC was increased and elimination rate decreased in an older population (60â€“68 years, n=6) compared to younger individuals (22â€“30 years, n=6).
After administration of the 400 mg extended-release Pentoxifylline tablet, plasma levels of the parent compound and its metabolites reach their maximum within 2 to 4 hours and remain constant over an extended period of time. Coadministration of Pentoxifylline tablets with meals resulted in an increase in mean Cmax and AUC by about 28% and 13% for pentoxifylline, respectively. Cmax for Metabolite 1 also increased by about 20%. The extended release of pentoxifylline from the tablet eliminates peaks and troughs in plasma levels for improved gastrointestinal tolerance.
|ATC Classification||C04AD03 - pentoxifylline; Belongs to the class of purine derivative agents used as peripheral vasodilators.|
Why is this medication prescribed?
Pentoxifylline is used to improve blood flow in patients with circulation problems to reduce aching, cramping, and tiredness in the hands and feet. It works by decreasing the thickness (viscosity) of blood. This change allows your blood to flow more easily, especially in the small blood vessels of the hands and feet.
This medication is sometimes prescribed for other uses; ask your doctor for more information.
How should this medicine be used?
Pentoxifylline may come as an extended-release (long-acting) tablet to take by mouth. It usually is taken three times a day. Do not break, crush, or chew the tablets; swallow them whole. Follow the directions on your prescription label carefully, and ask your doctor to explain any part you do not understand. Take pentoxifylline exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Although you may feel the effects of this medication in 2-4 weeks, you may need to take it for up to 8 weeks before you feel the full effect of pentoxifylline.
Pentoxifylline controls the symptoms of circulation problems, but does not cure them. Continue to take pentoxifylline even if you feel well. Do not stop taking pentoxifylline without talking to your doctor.
Other uses for this medicine
What special precautions should I follow?
- tell your doctor if you are allergic to caffeine-containing products (coffee, tea, colas), pentoxifylline, theobromine, theophylline or any other drugs.
- tell your doctor what prescription and nonprescription medications you are taking, especially anticoagulants ('blood thinners') such as warfarin and vitamins.
- tell your doctor if you have or have ever had kidney disease.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking pentoxifylline, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking pentoxifylline.
- you should know that this drug may make you drowsy or dizzy. Do not drive a car or operate machinery until you know how it affects you.
What special dietary instructions should I follow?
What should I do if I forget a dose?
What side effects can this medication cause?
If you experience either of the following symptoms, call your doctor immediately:
- fast heartbeat
What should I know about storage and disposal of this medication?
In case of emergency/overdose
In case of overdose, consult your doctor. If the victim has collapsed or is not breathing, consult local medical emergency services.
What other information should I know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to this medicine.
Do not let anyone else use your medication. If you still have symptoms and need further treatment, consult your doctor.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
Ref: U.S. National Library of Medicine.
This information is provided for reference only and not a replacement for and should only be used in conjunction with full consultation with a registered medical practitioner. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, mph-bd shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise.
|| See Brand Manufacturer's Prescribing Information |||| PENTOXIFYLLINE ||