liminfoTDM Reference
Free reference guide: TDM Reference
About TDM Reference
The TDM (Therapeutic Drug Monitoring) Reference is a searchable clinical cheat sheet covering therapeutic drug levels, peak/trough targets, toxicity thresholds, and pharmacokinetic parameters for drugs with narrow therapeutic indices. It organizes 25 entries into six categories: Basic Concepts (TDM overview, therapeutic range, peak/trough, PK parameters, steady state, Bayesian dosing), Antibiotics (vancomycin AUC/MIC, aminoglycosides traditional and extended-interval), Cardiovascular (digoxin, warfarin/INR), Neuropsychiatric (lithium, valproic acid, phenytoin, carbamazepine, phenobarbital, lamotrigine, levetiracetam), Immunosuppressants (cyclosporine, tacrolimus, sirolimus, mycophenolic acid), and Other Drugs (theophylline, high-dose methotrexate).
Each entry provides the therapeutic concentration range, recommended blood draw timing, toxicity signs and levels, half-life, and clinical pearls such as the Winter-Tozer correction for phenytoin or the Hartford Nomogram for aminoglycosides. The reference reflects current guidelines including the 2020 vancomycin AUC-guided dosing consensus.
All content loads in your browser with no server processing. The interface supports keyword search, category filtering, dark mode, and responsive layouts for use at the pharmacy workstation or bedside on a tablet.
Key Features
- Vancomycin TDM: AUC/MIC 400-600 target (2020 guideline), trough ranges, and nephrotoxicity thresholds
- Aminoglycoside monitoring: traditional peak/trough targets and extended-interval Hartford Nomogram dosing
- Neuropsychiatric drugs: lithium, valproic acid, phenytoin (with Winter-Tozer), carbamazepine autoinduction
- Immunosuppressant levels: cyclosporine C0/C2, tacrolimus, sirolimus, mycophenolic acid AUC targets
- Digoxin and warfarin/INR monitoring with toxicity signs and clinical target ranges
- Pharmacokinetic fundamentals: Vd, clearance, half-life, steady state, and Bayesian dose adjustment
- High-dose methotrexate TDM with 24/48/72-hour level thresholds and leucovorin rescue criteria
- Blood draw timing guidance: peak vs trough, distribution phase considerations, steady-state requirements
Frequently Asked Questions
What is the current vancomycin TDM recommendation?
The 2020 consensus guideline recommends AUC-guided monitoring with a target AUC of 400-600 mg*h/L and AUC/MIC ratio of at least 400, replacing the older trough-only approach. Trough levels of 15-20 mcg/mL for serious infections and 10-15 mcg/mL for general infections remain listed as supporting data. Nephrotoxicity risk increases with troughs above 20 mcg/mL.
How are aminoglycoside dosing strategies covered?
Two dosing strategies are detailed. Traditional dosing lists peak and trough targets for gentamicin/tobramycin (peak 5-10, trough <2 mcg/mL) and amikacin (peak 20-35, trough <10 mcg/mL). Extended-interval (once-daily) dosing uses 5-7 mg/kg for gentamicin/tobramycin and 15-20 mg/kg for amikacin, with the Hartford Nomogram applied to a random level drawn 6-14 hours post-dose.
What phenytoin-specific information is included?
The reference covers the total therapeutic range (10-20 mcg/mL), free level target (1-2 mcg/mL), and the nonlinear Michaelis-Menten pharmacokinetics that cause disproportionate level changes with small dose adjustments. It includes the Winter-Tozer equation for correcting levels in patients with low albumin, and toxicity milestones: nystagmus above 20 and ataxia above 30 mcg/mL.
Which immunosuppressant drugs are covered?
Four immunosuppressants are included: cyclosporine (trough C0 100-400 ng/mL, C2 800-1400 ng/mL), tacrolimus (trough 5-20 ng/mL by transplant phase), sirolimus (trough 5-15 ng/mL with 57-63 hour half-life), and mycophenolic acid (AUC0-12 target 30-60 mg*h/L). Each entry notes transplant-phase-specific targets, toxicity profiles, and assay considerations.
How does this reference explain steady state and blood draw timing?
The steady-state entry explains that 4-5 half-lives are needed to reach steady state, with examples like vancomycin (24-60 hours) and digoxin (7-10 days). Peak levels should be drawn after distribution is complete (e.g., 30 min post-IV for aminoglycosides, 6-8 hours for digoxin), and trough levels should be drawn within 30 minutes before the next dose.
What Bayesian dose adjustment information is provided?
The reference describes the Bayesian approach to dose individualization: using population pharmacokinetic parameters as prior information, incorporating patient-specific measured concentrations and timing, and computing posterior individual parameter estimates via MAP (Maximum A Posteriori). Software tools listed include NONMEM, InsightRx, DoseMeRx, and MwPharm.
Is lithium monitoring information included?
Yes. Lithium TDM covers acute-phase targets (0.8-1.2 mEq/L), maintenance targets (0.6-0.8 mEq/L, 0.4-0.6 for elderly), trough blood draw timing (12 hours pre-dose), toxicity thresholds (moderate above 1.5 with tremor/confusion, severe above 2.5 with seizure/coma), and the 18-24 hour half-life.
Who should use this TDM reference?
It is designed for clinical pharmacists, hospital pharmacists performing TDM consultations, physicians managing patients on narrow-therapeutic-index drugs, pharmacy students studying clinical pharmacokinetics, and nurses who draw drug levels. The format provides quick bedside access to therapeutic ranges and blood draw timing.