Therapeutic Drug Monitoring Clinical Guide FOURTH EDITION
Total Page:16
File Type:pdf, Size:1020Kb
DIAGNOSTICS Therapeutic Drug Monitoring Clinical Guide FOURTH EDITION 1 Therapeutic Drug Monitoring Clinical Guide FOURTH EDITION Authors Mike Hallworth, MA, MSc, FRCPath Former Consultant Biochemist Royal Shrewsbury Hospital United Kingdom Ian Watson, MSc, PhD, FRCPath Former Consultant Biochemist and Toxicologist University Hospital Aintree Liverpool, United Kingdom Editors of the David Holt, DSc, PhD Third Edition Susan Tett, PhD, BPharm (Hons), MPS Steven H. Wong, PhD, DABCC (TC), FACB 2 CONTENTS THERAPEUTIC DRUG MONITORING . 5 RUFINAMIDE . 81 WHY IS TDM NECESSARY? . 6 TIAGABINE . 83 WHICH DRUGS SHOULD BE MONITORED? . 8 TOPIRAMATE . 85 PRACTICAL CONSIDERATIONS . 10 VALPROATE . 87 CALCULATION OF DOSAGE ADJUSTMENT . 15 VIGABATRIN . 89 OTHER APPROACHES TO OPTIMIZING THERAPY — ZONISAMIDE . 91 PHARMACOGENETICS AND BIOMARKERS . 17 ANTIFUNGALS . 94 EFFECTIVENESS OF TDM – DOES IT HELP PATIENTS? . 19 POSOCONAZOLE/VORICONAZOLE . 95 REFERENCES . 21 ANTINEOPLASTICS . 98 WEBSITES . 23 BUSULFAN . 99 DRUG DATA PROFILES . 24 METHOTREXATE . 101 PREFACE . 24 ANTIRETROVIRALS . 104 ADDICTION THERAPEUTICS . 28 ANTIRETROVIRALS . 105 BUPRENORPHINE . 29 BRONCHODILATOR, ANALEPTIC . 108 METHADONE . 31 THEOPHYLLINE . 109 ANALGESICS . 34 CAFFEINE . 111 ACETAMINOPHEN (PARACETAMOL) . 35 CARDIAC AGENTS . 114 ACETYLSALICYLIC ACID (ASPIRIN) . 37 ANTI-ARRHYTHMICS MORPHINE . 39 AMIODARONE . 115 ANTIBIOTICS . 42 DISOPYRAMIDE . 117 AMINOGLYCOSIDES FLECAINIDE . 119 AMIKACIN . 43 LIDOCAINE . 121 GENTAMICIN . 45 CARDIAC GLYCOSIDES TOBRAMYCIN . 47 DIGOXIN . 123 OTHER ANTIBIOTICS IMMUNOSUPPRESSIVE AGENTS . 126 TEICOPLANIN . 49 CICLOSPORIN/CYCLOSPORINE . 127 VANCOMYCIN . 51 MYCOPHENOLATE . 129 ANTIEPILEPTICS . 54 SIROLIMUS . 131 CARBAMAZEPINE . 55 TACROLIMUS . 133 CLONAZEPAM . 57 PSYCHOACTIVE AGENTS . 136 ESLICARBAZEPINE ACETATE . 59 TRICYCLIC ANTIDEPRESSANTS ETHOSUXIMIDE . 61 AMITRIPTYLINE . 137 FELBAMATE . 63 OTHERS GABAPENTIN . 65 CLOZAPINE/OLANZAPINE . 139 LACOSAMIDE . 67 FLUOXETINE . 141 LAMOTRIGINE . 69 HALOPERIDOL . 143 LEVETIRACETAM . 71 LITHIUM . 145 OXCARBAZEPINE . 73 GLOSSARY . 147 PHENOBARBITAL/PRIMIDONE . 75 COMMON TRADE NAMES . 150 PHENYTOIN/FOSPHENYTOIN . 77 PREGABALIN . 79 3 4 THERAPEUTIC DRUG MONITORING during the 1960s and the development of the fundamental concepts of pharmacokinetics and pharmacodynamics. Therapeutic drug monitoring (TDM) is the use of drug concentration measurements in body fluids as an aid to the management of drug The scene was thus set for the surge of publications in the early 1970s therapy for the cure, alleviation or prevention of disease.1 It has on improving individualization of therapy by the monitoring of drug long been customary to adjust the dosage of drugs according to the concentration and appropriate adjustment of dose – the beginnings of characteristics of the individual being treated and the response TDM as we know it. The remaining barrier to widespread adoption obtained. Physicians have been most ready to do this when the of the concept — the availability of appropriate analytical methods — pharmacological response can be easily established by clinical means was removed during the 1970s by the development of commercially (e.g., antihypertensive drugs, analgesics, hypnotics) or by laboratory available homogeneous immunoassays for therapeutic drugs. The markers (e.g., anticoagulants, hypoglycemic agents, lipid-lowering ability to provide accurate and precise results simply and quickly drugs, hormone preparations). If there is a wide margin between the resulted in the explosive growth of TDM applications in the second MONITORING DRUG THERAPEUTIC toxic dose and the therapeutically effective dose, then monitoring half of the 1970s. may be unnecessary (e.g., penicillins). However where this is not the case and the drug’s action cannot readily be assessed clinically (e.g., in WHY IS TDM NECESSARY? the prophylaxis of seizure or mania) or when toxic effects cannot be As stated above, there are a number of drugs for which desired (or detected until severe or irreversible (e.g., aminoglycoside antibiotics, toxic) effects cannot readily be assessed clinically, but are related to immunosuppressants), then dosage individualization is much more the amount of drug in the body. In such cases, the logical approach difficult, though no less important. TDM now has an established place to control the effect of the drug is to limit the amount that is given to in enabling optimization of therapy with such agents. However, it must the patient. Pragmatically, using standard doses that will produce a be emphasized that clinical and other criteria remain important and satisfactory response in the majority of patients can achieve this. Such TDM should never be the sole basis for individualization of therapy. an approach has been widely used in medicine and is undoubtedly TDM has been established for a tightly defined group of drugs. It must effective for a large number of drugs (e.g., penicillins). The rapid be considered as a process where it (1) begins with a clinical question, development of pharmacogenomics is changing the crude “one dose (2) continues by devising a sampling strategy to answer that question, fits all” paradigm and will be discussed further later in this chapter. (3) determines one or more drug or metabolite concentrations using a For many (but not all) drugs, the primary determinant of clinical suitable method, and (4) interprets the results appropriately. response is the concentration that can be achieved at the site of action TDM has been routinely practised in clinical laboratories since the (the cell receptor, locus of infection, etc.). Often, wide variations in mid-1970s, following initial research work showing its potential value. drug concentration above a minimum or threshold level will make Buchthal2 showed in 1960 that there was a relationship between little difference to the clinical effect. However, for some drugs the plasma concentrations of phenytoin in patients being treated for desired effect (and various unwanted effects) may be very sensitive to epilepsy and the degree of seizure control attained. Baastrup and the drug concentration at a given time. Dr. Bernard Brodie suggested Schou demonstrated the relationship between plasma concentration in a keynote lecture given in 1967 that the marked heterogeneity of and pharmacological effect for lithium in 1967.3 This work coincided biological species with regard to drug metabolism meant that it would with the rise of clinical pharmacology as an independent discipline be preferable to relate drug effects to the plasma drug concentration rather than the dose. 5 6 BACK TABLE TO OF CONTENTS The problem with an approach based on standard dosing for some drugs PROCESSES INVOLVED IN DRUG HANDLING is illustrated in Figure 1, which shows the frequency distribution.