Exam aid · Lab and clinical values

Therapeutic Ranges & Targets

Ranges, sampling times and the clinical targets most often asked in hospital pharmacist papers.

Tables to memorise

Cover the right-hand column and test yourself before checking.

Drug	Range / when to sample
Digoxin	0.5–0.9 ng/mL (heart failure); ≥ 6 h post-dose
Lithium	0.4–1.0 mmol/L; 12 h post-dose
Phenytoin (total)	10–20 mg/L; trough
Carbamazepine	4–12 mg/L; trough, after autoinduction
Theophylline	10–20 mg/L (often 5–15)
Gentamicin (once daily)	Trough < 1 mg/L; nomogram-guided
Vancomycin	AUC/MIC 400–600 (serious MRSA)
Valproate	50–100 mg/L (poor correlation with effect)
Ciclosporin, tacrolimus	Trough, protocol-specific

Measure	Common target
Blood pressure (most adults)	< 140/90 mmHg; < 130/80 in many high-risk groups
HbA1c (most adults with diabetes)	< 7%
INR on warfarin (AF, VTE)	2.0–3.0
aPTT on heparin infusion	1.5–2.5 × control
LDL in very high CV risk	< 1.4 mmol/L and ≥ 50% reduction
Paracetamol maximum (adult)	4 g/day (lower in low weight or alcohol use)

Steady state takes 4–5 half-lives; sample after that unless loading was given.
Digoxin sampled less than 6 h after a dose is falsely high.
Hypokalaemia makes a 'normal' digoxin level toxic.
Lithium toxicity is precipitated by dehydration, NSAIDs, ACE inhibitors and thiazides.
Correct phenytoin for low albumin or measure the free level.

Lithium at 12, Digoxin after 6: Lithium levels 12 h post-dose; digoxin at least 6 h post-dose.

Attempt MCQs on these topics while the sheet is fresh. Anything you get wrong goes to your incorrect list for the next round.