Interferon alfa Theophylline

Peg Interferon Alfa 2b (PEG-Intron) [Antiviral/ Immunomodulator] WARNING Can cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disord s. Monitor pts closely Uses Rx Hep C Action Immune modulation Dose 1 mcg/kg/wk SQ 1.5 mcg/kg/wk combined w/ ribavirin Caution [C, X if used w/ ribavirin /-] w/ Hx psychiatric Contra Autoimmune H, decompensated Uvct Dz, hemoglobinopathy Disp Vials 50, 80, 120, 150 mcg/0.5 mL Redipen 50, 80,120,150 mcg/5 mL reconstitute w/ 0.7 mL w/ sterile water SE D ession, insomnia, suicidal behavior, GI upset, neutropenia, thrombocytopenia, alopecia, pruritus Interactions t Myelosuppression W/ antineoplastics t effects OF doxorubicin, theophylline t neurotox W7 vinblastine EMS See Peg Interf on Alfa-2a may cause flu-like Sxs... 

Drug Interactions According to the product label, interactions between Intron A and other drugs have not been fully evaluated. Caution should be exercised when administering Intron A therapy in combination with other potentially myelo-suppressive agents such as zidovudine. Concomitant use of alfa interferon and theophylline decreases theophylline clearance, resulting in a 100% increase in serum theophylline levels. 

Contraindications to interferon alfa therapy include hepatic decompensation, autoimmune disease, and history of cardiac arrhythmia. Caution is advised in the setting of psychiatric disease, epilepsy, thyroid disease, ischemic cardiac disease, severe renal insufficiency, and cytopenia. Alfa interferons are abortifacient in primates and should not be administered in pregnancy. Potential drug-drug interactions include increased theophylline levels and increased methadone levels. Co-administration with didanosine is not recommended because of a risk of hepatic failure, and co-administration with zidovudine may exacerbate cytopenias. 

INTERFERON ALFA BRONCHODILATORS -THEOPHYLLINE t theophylline levels Inhibition of theophylline metabolism Monitor theophylline levels before, during and after co-administration... 

A study in 5 patients with stable ehronic active hepatitis B and 4 healthy subjects found that 20 hours after being given a single 9- or 18-million unit intramuscular injection of interferon (recombinant human interferon alfa A), the clearance of theophylline (given as intravenous aminophylline) was approximately halved (range 33 to 81%) in 8 of the 9 subjects. The mean theophylline elimination half-life was increased from 6.3 to 10.7 hours (1.5 to sixfold increases). In the healthy subjects the theophylline clearances were noted to have returned to their former values 4 weeks after the study. ... 

Another study, in 11 healthy subjects given interferon alfa Roferon-A) 3 million units daily for 3 days, found that the terminal half-life and AUC of theophylline (given as aminophylline) were only increased by 10 to 15%, with a similar decrease in clearance. In 7 patients with cancer interferon alfa Intron-A) 3 million units given 3 times a week for 2 weeks decreased the clearance of a single 150-mg oral dose of theophylline by 33%. ... 

Interferon alfa inhibits the liver enzymes concerned with the metabolism of some drugs, such as theophylline. Therefore the metabolism of theophylline is reduced, and it accumulates. Interferon beta also appears to inhibit liver enzymes. ... 

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