At a Glance
Why Get Tested?
To determine the concentration of theophylline or caffeine in the blood to establish an appropriate dose and to maintain a therapeutic level
When to Get Tested?
At the start of drug therapy and at regular intervals to monitor the drug's concentration; when indicated, to detect low or excessive (potentially toxic) concentrations
A blood sample drawn from a vein in your arm or from pricking an infant's heel
Test Preparation Needed?
The Test Sample
What is being tested?
Theophylline and caffeine are methylxanthines – drugs that ease breathing and stimulate respiration. These tests measure the amount of theophylline or caffeine in the blood to help establish an appropriate dose and to maintain a therapeutic level.
Theophylline is one of several medications that may be taken by children and adults who have asthma and by adults who have chronic obstructive pulmonary disease (COPD). It is a bronchodilator with a narrow therapeutic window – too little theophylline is ineffective, too much can cause toxicity. Chronic theophylline toxicity is associated with an increased risk of seizures. Both acute and chronic toxicity can be life-threatening.
Theophylline may also be prescribed to treat apnea in premature neonates, but caffeine citrate is the preferred medication. Apnea compromises the amount of oxygen available to the body. It is a common and serious condition in premature neonates that must be promptly treated and closely monitored. While both medications can reduce episodes of apnea, caffeine has fewer side effects and, thus, a lower risk of toxicity. At very high doses, symptoms similar to those found with theophylline toxicity may be seen.
Establishing and maintaining therapeutic doses can be a challenge. Both theophylline and caffeine levels may need to be monitored because the range of concentrations in which the drugs are effective but not toxic is narrow and in some cases the dose given does not always correlate well with concentrations in the blood. The rate at which the drugs are metabolized will vary from person to person and is decreased in both the very young and the elderly. The drug levels may also be affected by underlying conditions such as liver disease, hypothyroidism, and by acute infection or illness. Many drugs interact and interfere with the metabolism of theophylline. They may increase or decrease its rate of metabolism.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm. In infants, blood may be collected by pricking a heel.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
Form temporarily unavailable
Due to a dramatic increase in the number of questions submitted to the volunteer laboratory scientists who respond to our users, we have had to limit the number of questions that can be submitted each day. Unfortunately, we have reached that limit today and are unable to accept your inquiry now. We understand that your questions are vital to your health and peace of mind, and recommend instead that you speak with your doctor or another healthcare professional. We apologize for this inconvenience.
This was not an easy step for us to take, as the volunteers on the response team are dedicated to the work they do and are often inspired by the help they can provide. We are actively seeking to expand our capability so that we can again accept and answer all user questions. We will accept and respond to the same limited number of questions tomorrow, but expect to resume the service, 24/7, as soon as possible.
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Yew, D. and Laczek, J. (Updated 2011 May 6) Caffeine Toxicity. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/821863-overview through http://emedicine.medscape.com. Accessed February 2012.
Hymel, G. (Updated 2011 July 12). Theophylline Toxicity in Emergency Medicine. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/818847-overview through http://emedicine.medscape.com. Accessed February 2012.
(2011 February 1). How Is Asthma Treated and Controlled? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/asthma/treatment.html through http://www.nhlbi.nih.gov. Accessed February 2012.
Heller, J. (Updated 2011 January 19). Aminophylline overdose. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002572.htm. Accessed February 2012.
(Updated 2012 January 6). Asthma Medicines: Long-term Control. Healthychildren.org [On-line information]. Available online at http://www.healthychildren.org/English/health-issues/conditions/allergies-asthma/pages/Asthma-Medicines-Long-term-Control.aspx through http://www.healthychildren.org. Accessed February 2012.
(© 1995–2012). Test ID: CAFF8754 Caffeine, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8754 through http://www.mayomedicallaboratories.com. Accessed February 2012.
(© 1995–2012). Test ID: THEO8661 Theophylline, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8661 through http://www.mayomedicallaboratories.com. Accessed February 2012.
Wise, R. (Modified 2010 January). Chronic Obstructive Pulmonary Disease. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed February 2012.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 367, 582.
Sources Used in Previous Reviews
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1280, 1490-1491.
Ram, F. (2006 March 8). Use of Theophylline in Chronic Obstructive Pulmonary Disease: Examining the Evidence. Medscape From Current Opinion in Pulmonary Medicine [On-line information]. Available online at http://www.medscape.com/viewarticle/524508 through http://www.medscape.com. Accessed on 9/14/08.
Kirkland, L. and Horn, A. (2008 May 29). Toxicity, Theophylline. eMedicine [On-line information]. Available online at http://www.emedicine.com/med/TOPIC2261.HTM through http://www.emedicine.com. Accessed on 9/14/08.
(© 2008). What is Asthma? American Lung Association [On-line information]. Available online at http://www.lungusa.org/site/c.dvLUK9O0E/b.4061173/apps/s/content.asp?ct=5314727 through http://www.lungusa.org. Accessed on 9/14/08.
(2007 December). Asthma Medications Chart. American Lung Association [On-line information]. Available online at http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=263990 through http://www.lungusa.org. Accessed on 9/14/08.
Buck, M. (2008 June). Caffeine Citrate for the Treatment of Apnea of Prematurity. Pediatric Pharmacotherapy v14 (6) [On-line information]. Available online at http://www.healthsystem.virginia.edu/internet/pediatrics/pharma-news/ through http://www.healthsystem.virginia.edu. Accessed on 9/14/08.
Natarajan, G. et. al. (2007 May 1). Therapeutic Drug Monitoring for Caffeine in Preterm Neonates: An Unnecessary Exercise? Pediatrics Vol. 119 No. 5 May 2007, Pp. 936-940. [On-line information]. Available online at http://pediatrics.aappublications.org/cgi/content/abstract/119/5/936 through http://pediatrics.aappublications.org. Accessed on 9/14/08.
(2007 August 1, Reviewed). Theophylline. MedlinePlus Drug Information [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a681006.html. Accessed on 9/14/08.
Perez, E. (2008 January 23). Aminophylline overdose. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002572.htm. Accessed on 9/14/08.
(© 2007). American Academy of Allergy, Asthma and Immunology. Tips to Remember: Asthma and allergy medications [On-line information]. Available online at http://www.aaaai.org/patients/publicedmat/tips/asthmaallergymedications.stm through http://www.aaaai.org. Accessed on 9/14/08.
Pesce, A. et. al. (1998). Standards of laboratory practice: theophylline and caffeine monitoring. Clinical Chemistry 44:5 1124–1128 [On-line information]. Available online at http://www.clinchem.org/cgi/content/full/44/5/1124 through http://www.clinchem.org.
Klein, J. (2008 June 26, Modified). Management of Neonatal Apnea. Iowa Neonatology Handbook: Pulmonary [On-line information]. Available online at http://www.uihealthcare.com/depts/med/pediatrics/iowaneonatologyhandbook/pulmonary/managementapnea.html through http://www.uihealthcare.com. Accessed on 9/21/08.
Baselt, R.C., (2002). Disposition of Toxic Drugs and Chemicals in Man, Sixth Edition. Biomedical Publications, Foster City, CA. Caffeine, Pp. 149 – 152; Theophylline, Pp. 1013 – 1017.
Hammett-Stabler, C.A., and A. Dasgupta (2007). Therapeutic Drug Monitoring Data: A Concise Guide, Third Edition. AACC Press, Washington, D.C., Pp. 222 – 230.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006. Appendix, Pp. 2304 and 2314.