Sorted By Test Name - Mayo Medical Laboratories

TOPI
81546
Reference Values:
Class IgE kU/L Interpretation
0 Negative
1 0.35-0.69 Equivocal
2 0.70-3.49 Positive
3 3.50-17.4 Positive
4 17.5-49.9 Strongly positive
5 50.0-99.9 Strongly positive
6 > or =100 Strongly positive Reference values
apply to all ages.
Clinical References: Homburger HA: Allergic diseases. In Clinical Diagnosis and Management by
Laboratory Methods. 21st edition. Edited by RA McPherson, MR Pincus. New York, WB Saunders
Company, 2007, Chapter 53, Part VI, pp 961-971
Topiramate, Serum
Clinical Information: Topiramate is a broad spectrum, anti-epileptic drug used to for various types of
seizures, Lennox-Gastaut syndrome (a type of childhood onset epilepsy), and migraine prophylaxis.
Topiramate blocks sodium channels, potentiates gamma-aminobutyric acid (GABA) activity, and inhibits
potentiation of the glutamate receptor, allowing the drug to block seizure spread. Topiramate shows
favorable pharmacokinetics, with good absorption, low protein binding, and minimal metabolism.
Elimination is predominantly renal as unaltered topiramate, with an elimination half-life of 20 to 30
hours. Serum concentrations of other anticonvulsant drugs are not significantly affected by the concurrent
administration of topiramate, with exception in individual patients on phenytoin exhibiting increased
phenytoin plasma concentrations after addition of topiramate. Coadministration of phenytoin or
carbamazepine decreases topiramate serum concentrations. Changes in co-therapy with phenytoin or
carbamazepine for patients stabilized on topiramate therapy may require dose adjustment due to these
instructions; therapeutic drug monitoring can assist this. As with other renally eliminated anticonvulsant
drugs, patients with impaired renal function exhibit decreased topiramate clearance.
Useful For: Monitoring serum concentrations of topiramate, particularly in patients with renal disease
or those coadministered phenytoin or carbamazepine Assessing compliance Assessing potential toxicity
Interpretation: Most individuals display optimal response to topiramate with serum levels 2.0
mcg/mL to 20.0 mcg/mL. Some individuals may respond well outside of this range, or may display
toxicity within the therapeutic range, thus interpretation should include clinical evaluation. Toxic levels
have not been well established. Therapeutic ranges are based on specimens drawn at trough (ie,
immediately before the next dose).
Reference Values:
2.0-20.0 mcg/mL
Clinical References: 1. Patslos PN, Berry DJ, Bourgeois BF, et al: Antiepileptic drugs-best practice
guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug
monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia 2008 Jul;49(7):1239-1276 2.
Johannessen SI, Tomsom T: Pharmacokinetic variablility of newer antiepileptic drugs: when is
monitoring needed? Clin Pharmacokinet 2006;45(11):1061-1075 3. Snozek CL, Rollins LA, Peterson
PW, Langman LJ: Comparison of a new serum topiramate immunoassay to fluorescence polarization
immunoassay. Ther Drug Monit 2010 Feb;32(1):107-111
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 1766