Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Interferons may slow down how quickly your liver processes theophylline type medicines.
What might happen:
The amount of theophylline in your blood may increase and cause toxic side effects, which may include loss of appetite, nausea, vomiting, nervousness, agitation, headache, fast and/or irregular heartbeat, or seizures.
What you should do about this interaction:
Make sure that your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. Your doctor may want to check the amount of theophylline in your blood more often while you are taking interferon and for a while after you stop taking interferon. Your doctor may need to change the amount of theophylline that you take while you you are taking interferon.If you experience any loss of appetite, nausea, vomiting, nervousness, agitation, headache, fast and/or irregular heartbeat, or seizures, contact your doctor right away.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Williams SJ, Baird-Lambert JA, Farrell GC. Inhibition of theophylline metabolism by interferon. Lancet 1987 Oct 24;2(8565):939-41.
2.Jonkman JH, Nicholson KG, Farrow PR, Eckert M, Grasmeijer G, Oosterhuis B, De Noord OE, Guentert TW. Effects of alpha-interferon on theophylline pharmacokinetics and metabolism. Br J Clin Pharmacol 1989 Jun; 27(6):795-802.
3.Pegasys 135 PFS (interferon alfa-2a) UK summary of product characteristics. Roche Products Limited June 20, 2002.
4.Pegasys (peginterferon alfa-2a) US prescribing information. Genentech USA, Inc. September, 2014.
5.Intron A (interfeon alfa-2b) US prescribing information. Schering Corporation December, 2011.
6.Okuno H, Takasu M, Kano H, Seki T, Shiozaki Y, Inoue K. Depression of drug-metabolizing activity in the human liver by interferon-beta. Hepatology 1993 Jan;17(1):65-9.
7.Wittayalertpanya S, Mahachai V. Caffeine clearance in patients with chronic viral hepatitis: before and after interferon therapy. J Med Assoc Thai 2001 Jun;84 Suppl 1:S189-96.