Ketamine

CLINICAL USE

Anaesthetic agent, analgesic

DOSE IN NORMAL RENAL FUNCTION

All doses are expressed as the base: 1.15 mg ketamine hydrochloride ≡1 mg of baseAnaesthesia: IM Short procedures: initially 6.5–13 mg/ —kg (10 mg/kg usually gives 12–25 minutes of surgical anaesthesia)Painful diagnostic manoeuvres: initially —4 mg/kgIV Injection: Initially 1–4.5 mg/kg over at least —60 seconds (2 mg/kg usually gives 5–10 minutes of surgical anaesthesia)IV Infusion: Induction total dose of —0.5–2 mg/kg; maintenance 10–45 mcg/kg/min; adjust rate according to response if infusion requiredAnalgesia: IM: 1.5–2 mg/kg —IV Infusion: 2–3 mg/kg or infusion rate —5–10 mg/hour of a solution of 5 mg/mL

PHARMACOKINETICS

Molecular weight :274.2 (as hydrochloride)

%Protein binding :

20 to 50 :

%Excreted unchanged in urine : 2 (88% as metabolites)

Volume of distribution (L/kg) :4

half-life – normal/ESRD (hrs) :2–4/ Unchanged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function

10 to 20 : Dose as in normal renal function

<10 : Dose as in normal renal function

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unlikely dialysability. Dose as in normal renal function

HD :Not Dialysed. Dose as in normal renal function

HDF/high flux :Unknown dialysability. Dose as in normal renal function

CAV/VVHD :Not Dialysed. Dose as in normal renal function

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsAdrenergic-neurone blockers: enhanced hypotensive effectAntihypertensives: enhanced hypotensive effect

Antidepressants: stop MAOIs 2 weeks before surgery; increased risk of arrhythmias and hypotension with tricyclics

Antipsychotics: enhanced hypotensive effectMemantine: increased risk of CNS toxicity, avoid concomitant use

ADMINISTRATION

Reconstition

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Route

IV bolus, IV Infusion, IM

Rate of Administration

Injection: over at least 60 seconds Infusion: Depends on clinical indication

Comments

For infusion add to glucose 5% or sodium chloride 0.9%, dilute to 1 mg/mL. In the USA can dilute to 2 mg/mL in fluid restricted patients (Dollery)Incompatible with diazepam and barbituratesUse infusion solutions within 24 hours 100 mg/mL strength must be diluted with an equal volume of water for injection, sodium chloride 0.9% or glucose 5% before useMinimum volume 50 mg/mL (undiluted). (UK Critical Care Group, Minimum Infusion Volumes for fluid restricted critically ill patients, 3rd Edition, 2006)

OTHER INFORMATION

Contraindicated in patients with severe hypertension; 1–2 mg/kg can increase arterial systolic blood pressure by approximately 20–40 mmHgAvoid in those prone to hallucinations or psychotic disorders4–10% can be removed by haemodialysis .

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