Clinical Chemistry Ii - Toxicology 2019.docx

UNIVERSITY OF SANTO TOMAS FACULTY OF PHARMACY | DEPARTMENT OF MEDICAL TECHNOLOGY THERAPEUTIC DRUG MONITORING PHARMACOLOGY PRINCIPLES 

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PHARMACODYNAMICS  processes of interaction of pharmacologically active substances with target sites, and the biochemical and physiologic consequences leading to therapeutic or adverse effects.  Drug Receptors  determine the quantitative relations between dose or concentration of drug and pharmacologic effects. The affinity determines concentration of drug required to form significant drugreceptor complexex  limit the maxiimal effect a drug may produce  responsible for selectivity of action  mediate actions of pharmacologic agonists and antagonists  Dose-Response  response is concentration dependent until a maximal effect is reached which then marks the plateau where there is saturation at the receptor or overload of a transport process PHARMACOKINETICS  Processes of uptake of drugs by the body, distribution into the tissue, biotransformations/metabolisms they undergo, and elimination of the drug and its metabolites from the body  Absorption  Depends on drug’s dissociating from its dosing form, dissolving in gastrintestinal fluids, then diffusing across the biological membrane barriers into the bloodstream.  Bioavailability – fraction of the drug absorbed in the systemic circulation Bioavailability > 70% is most desirable for drugs to be orally useful  Distribution  Metabolism  Biontransformation  Occurs at the liver  Phase I  Phase II  Clearance

THEREPAUETIC-DRUG MONITORING  

PEAK TROUGH

ANTI-EPILEPTIC DRUGS 

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PHENYTOIN | DILANTIN o Diphenylhydantoin o Primary or secondary generalized tonic-clonic seizures, partial or complex-partial seizures, and status epilepticus o Principal Metabolite : 5-(p-hydroxyphenyl)-5-phenyldantoin o Therapeutic Range : 10 – 20 ug/mL (40-79 umol/L) o Side Effect independent of plasma concentration: Gingival Hyperplasia o Toxic Effect Manifestations  > 20 ug/mL : Seizure Control not enhanced; Nystagmus and Ataxia  > 35 ug/mL : precipitate seizure activity o Specimen Collection  Peak : if px displays signs of intoxication; 4-5 hrs after the dose (up to 8 hrs)  Trough :monitor adequacy of therapy Carbamazepine | Tegretol o Same use with phenytoin with the addition of treating pain associated with trigeminal neuralgia and as a mood-stabilizing drug in bipolar disorder o

Endocrinology/wynlor| 1