nhs forth valley formulary 11 - Community Pharmacy

Forth Valley Formulary Eleventh Edition 2012/13Appendix 12Therapeutic Drug Monitoring GuidelinesDrugTime tosteady stateDRUGSIdeal Sampling time Target range CommentsCarbamazepine2-3 weeks(newtherapy)2-4 days(dosechange)7-10 days(depends onrenalfunction)Pre dose (not critical) 4 – 12 mg/L Metabolised bythe liver,autoinductionSee BNF forinteractionsDigoxin> 6 hours post dose 0.5 – 2.0μg/L Mainly renalexcretionSee BNF forinteractionsLithium 5-7 days 12 hours post dose 0.4-1.0 mmol/L Renal excretionPhenytoin 2-3 weeks Pre dose (not critical) 10-20 mg/L Metabolised inliver. Non linearincrease inconc with dose.Theophylline 2-3 days 8-12 hours 10-20 mg/L Metabolised inpost dosethe liver.Valproic acid 3 days Pre dose 40-100 mg/L Metabolised inthe liver. Levelsdo not correlatewell withtherapeuticeffectPage 79