Clinical Pharmacokinetics
Therapeutic drug
monitoring,
calculated.
Dosing, correction and monitoring tools built for the pharmacy bench — vancomycin, aminoglycosides, phenytoin, methotrexate, acetaminophen and more.
CrCl
CrCl / IBW
Cockcroft-Gault, ideal & adjusted body weight
VAN
Vancomycin
Loading dose, population & patient-specific PK, AUC
AG
Aminoglycosides
Gentamicin & amikacin — MDD, SDD Hartford, neonates
PHT
Phenytoin
Corrected level, loading dose, Graves-Cloyd, M-M adjustment
APAP
Acetaminophen
Rumack-Matthew nomogram, hepatotoxicity risk
MTX
Methotrexate
Leucovorin rescue dose lookup, high-dose monitoring
Rx
Drug Reference
Digoxin, lithium, immunosuppressants, AEDs
TDM
Sampling Guide
Serum sampling times reference for all drugs
i
About
References, disclaimer and clinical notes
For use by qualified healthcare professionals only. All results must be interpreted in the full clinical context of the patient.
∑Formula Reference
▼
Ideal Body Weight (IBW) — Male
IBW = 50 + 2.3 × (height_inches − 60)
height_inches = height (cm) ÷ 2.54
Ideal Body Weight (IBW) — Female
IBW = 45.5 + 2.3 × (height_inches − 60)
Adjusted Body Weight (ABW)
ABW = IBW + 0.4 × (actual_BW − IBW)
Applied only when actual_BW > IBW × 1.2 (i.e. obese patient)
Creatinine Clearance (Cockcroft-Gault) ⚠ verify
CrCl = (140 − age) × weight ÷ (0.814 × SCr)
age = patient age in years
weight = ABW if obese, otherwise actual body weight (kg)
SCr = serum creatinine in µmol/L
Result × 0.85 if patient is female
weight = ABW if obese, otherwise actual body weight (kg)
SCr = serum creatinine in µmol/L
Result × 0.85 if patient is female
Source: Cockcroft-Gault equation, 1976. Coefficient 0.814 = 72 ÷ 88.4 (mg/dL→µmol/L conversion).
Patient Details
Results
Reference — Renal Function Classification
| Stage | CrCl (mL/min) | Dose Adjustment |
|---|---|---|
| Normal | ≥ 90 | Full dose |
| Mild impairment | 60–89 | Usually full dose |
| Moderate impairment | 30–59 | Dose reduction often needed |
| Severe impairment | 15–29 | Significant reduction needed |
| Renal failure | < 15 | Use with extreme caution |
∑Formula Reference — Vancomycin
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Loading Dose
LD = dose_per_kg × weight (15–20 or 25–30 mg/kg)
weight = actual body weight (kg)
Incremental Loading Dose
Incremental LD = (C_desired − C_current) × 0.7 × weight
C_desired / C_current = target / measured level (mcg/mL) · 0.7 = population Vd (L/kg)
Elimination Rate Constant (Ke) — Population (Matzke) ⚠ verify
Ke = 0.00083 × CrCl + 0.0044
CrCl = creatinine clearance (mL/min)
Source: Matzke GR et al., Antimicrob Agents Chemother, 1984.
Half-life / Volume of Distribution
t½ = 0.693 ÷ Ke | Vd = 0.7 × weight (L)
Cmax / Cmin (Steady-State)
Cmax = (D÷t_inf)×(1−e^(−Ke×t_inf)) ÷ (Ke×Vd×(1−e^(−Ke×τ)))
Cmin = Cmax × e^(−Ke×(τ−t_inf))
D = dose (mg) · t_inf = infusion time (h) · τ = dosing interval (h)
AUC₂₄
AUC₂₄ = (D ÷ Vd ÷ Ke) × (24 ÷ τ)
Target range: 400–600 mg·h/L
Patient-Specific Ke (2-level method)
Ke = ln(Cpost ÷ Cpre) ÷ (t_post − t_pre)
Cpre / Cpost = trough / peak level (mcg/mL) · t_pre / t_post = sample times (h)
New Dose (from patient PK)
D_new = C_target×Ke×Vd×(1−e^(−Ke×τ)) ÷ ((1−e^(−Ke×t_inf))×e^(−Ke×(τ−t_inf)))
C_target = desired trough level (mcg/mL)
Two Steady-State / Two Random Levels (Michaelis-Menten)
Km = (D1×L2 − D2×L1) ÷ (D2 − D1) | Vmax = D1×(Km+L1)÷L1
D_new = Vmax × C_desired ÷ (Km + C_desired)
D1, D2 = two different doses · L1, L2 = corresponding steady-state levels
Loading & Incremental Loading Dose
Loading Dose
Population PK — Predict Level from Dose
Uses population Ke (Matzke equation). Enter CrCl from the CrCl tab.
Estimated Levels
Patient-Specific PK — Two Measured Levels
Cpre: 30 min before dose | Cpost: 1 h after end of infusion. Collect at steady state (3rd–4th dose).
Patient PK & New Dose
One Steady-State Concentration
Obtain one steady-state trough level. Use population Vd (0.7 L/kg) to back-calculate patient Ke, then suggest new dose.
Estimated PK & New Dose
Two Steady-State Concentrations (Different Doses)
Obtain two steady-state trough levels at two different doses. Used to estimate patient Vmax & Km (Michaelis-Menten).
Michaelis-Menten PK & New Dose
Two Random Levels Post 1st Dose — Renal Impaired Patients
For renally impaired patients. Obtain two random levels after the 1st dose, at least 2 half-lives apart.
Patient PK & Suggested New Dose
Therapeutic Targets & Sampling Times
| Indication | Target Trough (mcg/mL) |
|---|---|
| Non-complicated infection | 10–15 |
| Complicated infection | 15–20 |
| Continuous infusion (SS) | 15–25 |
| AUC/MIC target | 400–600 mg·h/L |
Sampling:
• Trough: 30 min before next dose (3rd–4th dose, steady state)
• Peak: 1 h after 1-h infusion completed
• After LD: 2–3 h after administration
• Continuous infusion: 12–24 h after starting (any time at SS)
• With LD: 12–24 h after LD | Without LD: 7–10 days (normal renal) / 7–14 days (renal impaired)
• Trough: 30 min before next dose (3rd–4th dose, steady state)
• Peak: 1 h after 1-h infusion completed
• After LD: 2–3 h after administration
• Continuous infusion: 12–24 h after starting (any time at SS)
• With LD: 12–24 h after LD | Without LD: 7–10 days (normal renal) / 7–14 days (renal impaired)
∑Formula Reference — Aminoglycosides
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Elimination Rate Constant (Ke) — Population ⚠ verify
Ke = 0.00293 × CrCl + 0.014
CrCl = creatinine clearance (mL/min)
Volume of Distribution (Vd)
Vd (Gentamicin) = 0.26 × weight | Vd (Amikacin) = 0.25 × weight
weight = body weight (kg)
Cmax / Cmin (Steady-State, MDD)
Cmax = (D÷t_inf)×(1−e^(−Ke×t_inf)) ÷ (Ke×Vd×(1−e^(−Ke×τ)))
Cmin = Cmax × e^(−Ke×(τ−t_inf))
D = dose (mg) · t_inf = infusion time (h) · τ = dosing interval (h)
Patient-Specific Ke & New Dose (MDD)
dt = τ − t_inf − 0.5 | Ke = ln(Cpost ÷ Cpre) ÷ dt
D_new = D_current × (C_target ÷ Cpost)
Cpre / Cpost = measured trough / peak (mcg/mL) · 0.5 h = sampling delay after infusion
Suggested Dosing Interval
τ_new = round(3 × t½ ÷ 6) × 6
Rounds interval to nearest practical 6-hour block (≈3 half-lives)
SDD Hartford — Dose
Dose (Gentamicin) = 5 mg/kg × ABW | Dose (Amikacin) = 15 mg/kg × ABW
SDD Hartford — Interval (by CrCl)
CrCl ≥60 → q24h | 40–59 → q36h | <40 → q48h
Confirmed using random level taken 6–14 h post-dose against Hartford nomogram
Neonatal Dosing
Fixed dose/interval bands by gestational age (GA) and postnatal age (PNA) — see table in Neonates tab. Not formula-derived; based on published paediatric dosing protocols.
MDD — Predict Cmax & Cmin from Current Dose
Estimated Cmax & Cmin
MDD — Patient PK & New Dose
Cpre: 30 min before dose | Cpost: 30 min after 30-min infusion. Collect at steady state (3rd–4th dose).
Patient PK & Suggested New Dose
Single Daily Dose — Hartford Nomogram
SDD Dose & Interval
Neonates / Paediatrics
Neonatal Dosing
Target Ranges
| Parameter | Gentamicin | Amikacin |
|---|---|---|
| MDD Peak (Cmax) | 5–10 mcg/mL | 25–40 mcg/mL |
| MDD Trough (Cmin) | <2 mcg/mL | <10 mcg/mL |
| Synergistic Trough | <1 mcg/mL | — |
| MDD+Dialysis Trough | <2 mcg/mL | <10 mcg/mL |
| SDD Peak target | 10–30 mcg/mL | 60 mcg/mL (adjustable) |
| Neonates Peak (MDD) | 5–12 mcg/mL | 20–30 mcg/mL |
| Neonates Trough | <1 mcg/mL | <5 mcg/mL |
| Neonates+Synergy Trough | <1 mcg/mL | — |
| MDD + Dialysis Trough | <2 mcg/mL | <10 mcg/mL |
DFP (Dosing Frequency Period):
• Gentamicin DFP: interval based on CrCl — used in SDD Hartford nomogram
• Amikacin DFP: similarly interval-based
• Target DFP is read from Hartford nomogram (6–14 h post-dose level)
• Gentamicin DFP: interval based on CrCl — used in SDD Hartford nomogram
• Amikacin DFP: similarly interval-based
• Target DFP is read from Hartford nomogram (6–14 h post-dose level)
∑Formula Reference — Phenytoin
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Step 1 — Check Albumin (assume normal if unavailable)
Albumin ≥ 2.5 g/dL → no correction needed, use measured level directly
Step 2 — If Albumin < 2.5 g/dL: Corrected Concentration (CrCl ≥10 mL/min or unknown)
C_corrected = C_measured ÷ (0.9 × (Albumin ÷ 4.4) + 0.1)
C_measured = lab-reported total phenytoin level (mcg/mL)
Albumin = serum albumin (g/dL)
Albumin = serum albumin (g/dL)
Step 2 — If Albumin < 2.5 g/dL AND CrCl < 10 mL/min
C_corrected = C_measured ÷ (0.48 × 0.9 × (Albumin ÷ 4.4) + 0.1)
Dose Adjustment (Michaelis-Menten, two dose-level pairs)
Km = (D1×L2 − D2×L1) ÷ (D2 − D1)
Vmax = D1 × (Km + L1) ÷ L1
D_new = Vmax × C_desired ÷ (Km + C_desired)
D1, D2 = two doses tried (mg/day) · L1, L2 = corresponding corrected steady-state levels (mcg/mL) · C_desired = target level
Loading Dose — Phenytoin-naïve / Incremental (already on phenytoin)
Naïve: LD = Cp_desired × Vd × BW ÷ (S × F)
Incremental: LD = (Cp_desired − Cp_measured) × Vd × BW ÷ (S × F)
Vd = volume of distribution (L/kg) — enter manually (guide ranges: Neonate premature 1–1.2, term 0.8–0.9 · Infant 0.7–0.8 · Pediatric 0.7 · Adult 0.65–0.7 L/kg)
S = salt factor (IV/Capsule 0.92, Susp/Chew Tab 1) · F = bioavailability (all routes = 1)
S = salt factor (IV/Capsule 0.92, Susp/Chew Tab 1) · F = bioavailability (all routes = 1)
Graves-Cloyd Method — Single-Level Dose Adjustment
D_new = D_old × (Css_desired ÷ Css_old)0.2
D_old = current dose (mg/day) · Css_old = current steady-state level (mcg/mL) · Css_desired = target level (mcg/mL)
Verified against Graves NM et al., Ther Drug Monit 1986;8(4):427-33 (original exponent 0.2, n=59). A later re-analysis of the same dataset reported b=−0.804, i.e. exponent 0.196 — essentially the same value. The "0.199" in the source slide appears to be an OCR/legibility artifact of 0.2/0.196.
Time to Withhold Therapy — Toxic Level → Desired Level
T (days) = [Km × ln(Cp_measured ÷ Cp_desired) + (Cp_measured − Cp_desired)] × Vd ÷ Vm
Cp_measured = current toxic level · Cp_desired = target level (mcg/mL) · Vd = Vd/kg × body weight (L) · Vm = Vm/kg × body weight (mg/day) · Km in mg/L
Adult — Local population: Vm 8.45 mg/kg/day, Km 6.72 mg/L | Adult — Literature: Vm 7 mg/kg/day, Km 4 mg/L
Infant: Vm 10–14 mg/kg/day (midpoint 12 used), Km 6 mg/L
Vd: Adult 0.65–0.7 L/kg (midpoint 0.675) · Infant 0.7–0.8 L/kg (midpoint 0.75)
Infant: Vm 10–14 mg/kg/day (midpoint 12 used), Km 6 mg/L
Vd: Adult 0.65–0.7 L/kg (midpoint 0.675) · Infant 0.7–0.8 L/kg (midpoint 0.75)
⚠ Pediatric/Neonatal Km & Vm not provided in source guide — calculator currently supports Adult and Infant only.
Corrected Phenytoin Concentration
Always check Albumin (and CrCl/BUSE-Creat) first — if unavailable, assume normal. If Albumin ≥2.5 g/dL: no correction needed, use the measured level as-is. If Albumin <2.5 g/dL, the correction equation is applied automatically below (renal-failure variant only if CrCl is also <10 mL/min).
Corrected Concentration
Loading Dose — Naïve / Incremental
Leave Cp Measured blank for a phenytoin-naïve patient (uses the naïve formula). Enter a value to calculate an incremental loading dose for a patient already on phenytoin. Vd is entered manually — guide ranges: Neonate premature 1–1.2, term 0.8–0.9 · Infant 0.7–0.8 · Pediatric 0.7 · Adult 0.65–0.7 L/kg.
Loading Dose
Dose Adjustment — Two Dose-Level Pairs (Michaelis-Menten)
Suggested New Dose
Graves-Cloyd Method — Single-Level Dose Adjustment
Uses a single steady-state level (instead of two dose-level pairs) to predict a new dose. Formula verified against Graves NM et al., Ther Drug Monit 1986;8(4):427-33 (exponent 0.2).
Suggested New Dose
Time to Withhold Therapy — Toxic Phenytoin Level
For use when the level is in the toxic range and therapy needs to be withheld until it decays to a safe/desired level (Michaelis-Menten elimination). Km/Vm data is only available for Adult and Infant in the source guide — Pediatric/Neonatal values were not provided, so this calculator does not cover those groups yet.
Time to Withhold Therapy
Therapeutic Ranges & Sampling
| Indication | Target Range |
|---|---|
| Epilepsy | 10–20 mcg/mL |
| Status epilepticus | 15–40 mcg/mL |
| Refractory status epilepticus | >70 mcg/mL |
| Psychiatric disorders | 50–125 mcg/mL |
Sampling:
• IV: 2 h after end of infusion
• Oral: At least 6 h after dose
• Dose change monitoring: 2–5 days after initiation/change
• High-risk group (enzyme-inducing drugs: CBZ, PHY, Phenobarbitone, Rifampicin; HIV; Alcoholics): more frequent monitoring
• IV: 2 h after end of infusion
• Oral: At least 6 h after dose
• Dose change monitoring: 2–5 days after initiation/change
• High-risk group (enzyme-inducing drugs: CBZ, PHY, Phenobarbitone, Rifampicin; HIV; Alcoholics): more frequent monitoring
∑Formula Reference — Acetaminophen
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Rumack-Matthew Treatment Line
Treatment_line = 150 × 10^(−(t−4) × log₁₀(150÷4.7) ÷ 20)
t = hours post-ingestion (valid range: 4–24 h only)
Line passes through 150 mcg/mL at 4 h and 4.7 mcg/mL at 24 h
Line passes through 150 mcg/mL at 4 h and 4.7 mcg/mL at 24 h
Possible Risk Line
Risk_line (standard) = Treatment_line × 0.75
Risk_line (high-risk group) = Treatment_line × 0.50
High-risk = enzyme inducers, chronic alcohol use, malnutrition/fasting
Source: White S. & Rumack B., Annals of Emergency Medicine, 2005.
Toxicity Assessment
For single acute ingestion only. Obtain level at 4 h post-ingestion. Unknown time: two samples 2 h apart.
Risk Assessment
Rumack-Matthew Nomogram
References: 1. MOH Malaysia, 2019. Clinical PK Pharmacy Handbook, 2nd Ed. 2. White & Rumack, 2005. AEM 45(5):563. 3. Bauer, 2008. Applied Clinical Pharmacokinetics.
Sampling time is based on the patient's specific MTX protocol — typically 24, 48, 72 (and 96) hours post-infusion start.
Leucovorin Rescue Dose Lookup
Leucovorin Recommendation
Leucovorin Rescue Protocol Summary
| Hours | MTX (µmol/L) | Leucovorin (mg/m² QID) |
|---|---|---|
| Post 24 h | 10.1–12 | 90 |
| Post 24 h | 12.1–18 | 150 |
| Post 24 h | >18 | 300 |
| Post 48 h | 1.1–1.8 | 15 |
| Post 48 h | 1.9–2.8 | 30 |
| Post 48 h | 2.9–8.5 | 90 |
| Post 48 h | 8.6–18 | 150 |
| Post 48 h | >18 | 300 |
| Post 72 h | 0.1–0.29 | 10 |
| Post 72 h | 0.3–1.8 | 15 |
| Post 72 h | 1.9–2.8 | 30 |
| Post 72 h | 2.9–9.8 | 90 |
| Post 72 h | 9.9–19 | 150 |
| Post 72 h | >19 | 300 |
| Post 96 h | Same brackets as 72 h | — |
At 96 h, refer to the same concentration brackets as 72 h. Further serum MTX levels may be done daily thereafter.
Acceptable Range — High-Dose Methotrexate
| Time | Acceptable Level |
|---|---|
| 24 hours | 5–10 µmol/L |
| 48 hours | 0.5–1 µmol/L |
| 72 hours | <0.1 µmol/L |
| Random | <0.05 µmol/L (undetectable) |
Sampling: Based on the patient's specific protocol.
Hydration & urine alkalinisation (pH >7) mandatory throughout to prevent nephrotoxicity.
Renal function: Monitor SCr — impaired clearance prolongs MTX exposure and toxicity risk.
Hydration & urine alkalinisation (pH >7) mandatory throughout to prevent nephrotoxicity.
Renal function: Monitor SCr — impaired clearance prolongs MTX exposure and toxicity risk.
Digoxin
| Indication | Target Range |
|---|---|
| Heart Failure (CHF) | 0.5–0.9 ng/mL |
| Atrial Fibrillation (AF) | 0.8–2.0 ng/mL |
| General range | 0.8–2.0 ng/mL |
Sampling: At least 6 h post dose (trough preferred; must be post-distribution phase)
Time to SS: 5–7 days (normal renal); longer in renal impairment
Toxicity >2 ng/mL — nausea, bradycardia, arrhythmia
Tube: Plain/SST (avoid EDTA — causes falsely high levels in some assays)
Time to SS: 5–7 days (normal renal); longer in renal impairment
Toxicity >2 ng/mL — nausea, bradycardia, arrhythmia
Tube: Plain/SST (avoid EDTA — causes falsely high levels in some assays)
Lithium
| Indication | Target Range |
|---|---|
| Acute mania (treatment) | 0.8–1.2 mmol/L |
| Maintenance (prophylaxis) | 0.5–1.0 mmol/L |
| General therapeutic range | 0.5–1.5 mmol/L |
Sampling: 12 h post last dose (trough) — standardized 12-h level
Time to SS: 4–5 days
Toxicity: >1.5 mmol/L — tremor, ataxia; >2.0 mmol/L — severe toxicity
Note: Narrow therapeutic index. Monitor renal function, thyroid, calcium regularly.
Time to SS: 4–5 days
Toxicity: >1.5 mmol/L — tremor, ataxia; >2.0 mmol/L — severe toxicity
Note: Narrow therapeutic index. Monitor renal function, thyroid, calcium regularly.
Immunosuppressants
⚠ EDTA tube required for Cyclosporin, Tacrolimus, and Sirolimus. Plain tube gives falsely LOW levels due to drug binding to red cells.
| Drug | Target Range | Indication |
|---|---|---|
| Cyclosporin (CSA) | ~100–500 mcg/L | Varies by organ/phase |
| Tacrolimus | 4–24 ng/mL | Varies by organ/phase |
| Sirolimus | 5–20 ng/mL | Varies by organ/phase |
Cyclosporin (CSA):
• Induction phase: ~600–1700 mcg/L (whole blood trough)
• Maintenance: ~100–500 mcg/L (indication-specific)
• Sampling: Pre-dose trough (C0), or 2 h post dose (C2 monitoring)
• Blood: Adult 3 mL, Paed 2 mL
Tacrolimus / Sirolimus:
• Sampling: Pre-dose trough (immediately before next dose)
• Ranges are indication- and centre-specific
• Time to SS: 2–4 days (Tacrolimus); 3–5 days (Sirolimus)
• ESRD affects elimination: Sirolimus t½ up to 15–20 days
• Induction phase: ~600–1700 mcg/L (whole blood trough)
• Maintenance: ~100–500 mcg/L (indication-specific)
• Sampling: Pre-dose trough (C0), or 2 h post dose (C2 monitoring)
• Blood: Adult 3 mL, Paed 2 mL
Tacrolimus / Sirolimus:
• Sampling: Pre-dose trough (immediately before next dose)
• Ranges are indication- and centre-specific
• Time to SS: 2–4 days (Tacrolimus); 3–5 days (Sirolimus)
• ESRD affects elimination: Sirolimus t½ up to 15–20 days
Antiepileptic Drugs (AEDs)
| Drug | Therapeutic Range | Sampling |
|---|---|---|
| Phenytoin | 10–20 mcg/mL | ≥6 h post oral dose |
| Phenobarbitone | 15–40 mcg/mL | Pre-dose trough |
| Carbamazepine (CBZ) | 4–12 mcg/mL | Pre-dose trough |
| Valproate (VPA) | 50–100 mcg/mL | Pre-dose trough |
| Psychiatric (VPA) | 50–125 mcg/mL | Pre-dose trough |
Time to SS:
• Phenytoin: 5–14 days (nonlinear PK — variable)
• Phenobarbitone: 2–3 weeks (induction phase)
• Carbamazepine: 2–4 days (initial); re-check after 2–4 weeks due to autoinduction
• Valproate: 2–4 days
Dose change monitoring: Recheck level 2–5 days after any dose change (except Phenobarbitone and CBZ — longer).
• Phenytoin: 5–14 days (nonlinear PK — variable)
• Phenobarbitone: 2–3 weeks (induction phase)
• Carbamazepine: 2–4 days (initial); re-check after 2–4 weeks due to autoinduction
• Valproate: 2–4 days
Dose change monitoring: Recheck level 2–5 days after any dose change (except Phenobarbitone and CBZ — longer).
Methotrexate (High-Dose)
For the full Leucovorin rescue dose lookup calculator, see the dedicated Methotrexate module on the home screen.
| Time Post Infusion | Acceptable Level (µmol/L) |
|---|---|
| 24 hours | 5–10 |
| 48 hours | 0.5–1 |
| 72 hours | < 0.1 |
| Random | < 0.05 (undetectable) |
Sampling: Based on patient's specific protocol; levels typically at 24, 48, 72 (and 96) h post infusion start
Leucovorin rescue: Continue until MTX level <0.1 µmol/L
Hydration & urine alkalinisation (pH >7) mandatory to prevent nephrotoxicity
Renal function: Monitor SCr — impaired clearance → prolonged toxicity
Leucovorin rescue: Continue until MTX level <0.1 µmol/L
Hydration & urine alkalinisation (pH >7) mandatory to prevent nephrotoxicity
Renal function: Monitor SCr — impaired clearance → prolonged toxicity
Other Drugs — General Reference
| Drug | Target Range | Sampling Time |
|---|---|---|
| Theophylline | 10–20 mcg/mL | Trough (pre-dose) |
| Amiodarone | 0.5–2.5 mg/L | Any time (long t½) |
| Gentamicin (synergy) | 3–5 mcg/mL (peak) | 30 min post infusion |
| Flucytosine (5-FC) | 25–50 mg/L | 2 h post dose (peak) |
Blood sample notes:
• Adult: 3 mL plain tube (unless EDTA specified)
• Paediatric: 2 mL
• EDTA tube required: Cyclosporin, Tacrolimus, Sirolimus only
• Adult: 3 mL plain tube (unless EDTA specified)
• Paediatric: 2 mL
• EDTA tube required: Cyclosporin, Tacrolimus, Sirolimus only
Vancomycin
| Method | Sample | Timing |
|---|---|---|
| Intermittent — Trough | Pre-dose | 30 min before next dose (3rd–4th dose) |
| Intermittent — Peak | Post-infusion | 1 h after 1-h infusion completed |
| After Loading Dose | Post-LD | 2–3 h after administration |
| Continuous Infusion | Any time (SS) | 12–24 h after starting infusion |
| With LD | — | 12–24 h after LD |
| Without LD | — | 7–14 days (time to SS) |
Aminoglycosides — MDD
| Dose | Sample | Timing |
|---|---|---|
| 3rd or 4th dose | Trough (pre) | 30 min before dose |
| 3rd or 4th dose | Peak (post) | 30 min after 30-min infusion completed |
| 2nd dose (neonates) | 1st sample | Post 2 hours |
| 2nd dose (neonates) | 2nd sample | Post 6 hours |
Aminoglycosides — SDD (Hartford)
| Timing | Notes |
|---|---|
| 6–14 h post first dose | Random level to determine dosing interval |
| After 24 h (after 1st stat dose) or pre-HD | For renal impaired patients |
| Adults: 5–7 days | Or any two post-sampling ≥2 half-lives apart |
Not applicable if drug infused over more than 1 hour.
Phenytoin
| Route | Timing |
|---|---|
| IV | 2 h after end of infusion (if rapid concentration needed) |
| Oral | At least 6 h after dose |
| After dose change | 2–5 days after initiation/change |
Acetaminophen (Toxicity)
| Scenario | Timing |
|---|---|
| Single acute ingestion | 4 h post ingestion (minimum) |
| Unknown ingestion time | 2 samples × 2 h apart |
| Toxicity assessment | Valid for 4–24 h post-ingestion only |
Other Drugs
| Drug | Sampling Time | Time to SS |
|---|---|---|
| Digoxin | ≥6 h post dose (trough) | 5–7 days |
| Lithium | 12 h post last dose | 4–5 days |
| Cyclosporin | Pre-dose trough (C0) or 2 h post (C2) | Varies |
| Tacrolimus | Pre-dose trough | 2–4 days |
| Sirolimus | Pre-dose trough | 3–5 days |
| Phenobarbitone | Pre-dose trough | 2–3 weeks (induction) |
| Carbamazepine | Pre-dose trough | 2–4 days (re-check at 2–4 wks) |
| Valproate | Pre-dose trough | 2–4 days |
| MTX (high-dose) | 24/48/72 h post infusion | N/A |
Blood sample: Adult 3 mL · Paediatric 2 mL · Plain tube (except EDTA for Cyclosporin/Tacrolimus/Sirolimus)
References
1. Ministry of Health Malaysia, 2019. Clinical Pharmacokinetics Pharmacy Handbook, 2nd Edition.
2. White S. & Rumack B., 2005. The Acetaminophen Toxicity Equations. Annals of Emergency Medicine, 45(5):563-564.
3. Bauer L., 2008. Applied Clinical Pharmacokinetics, 2nd ed. McGraw-Hill.
4. Hartford Nomogram — Aminoglycosides Single Daily Dose.
5. Matzke GR et al. Vancomycin pharmacokinetics in patients with various degrees of renal function. Antimicrob Agents Chemother, 1984.
6. Rozario F.D., Soo H.H., Hu M., Chew P.H., 2020. Sarawak Handbook of Medical Emergencies, 4th Ed. Malaysia: CE Publishing.
2. White S. & Rumack B., 2005. The Acetaminophen Toxicity Equations. Annals of Emergency Medicine, 45(5):563-564.
3. Bauer L., 2008. Applied Clinical Pharmacokinetics, 2nd ed. McGraw-Hill.
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Credits
© All rights reserved.
Created by Charlie Ting · Validated by Pharmacist Rachel Wang Li Ting
Created by Charlie Ting · Validated by Pharmacist Rachel Wang Li Ting
⚠ For clinical use by trained pharmacists only. Always verify calculations independently.
This application is a clinical decision support tool. All pharmacokinetic calculations are population-based estimates. Results must always be interpreted within the full clinical context of the individual patient. The developers accept no liability for clinical decisions made based on outputs from this tool.