TDM and Toxicology Flashcards
What drugs need monitoring
Drugs that are always measured
-Lithium -Antibiotics -Vancomycin -Aminoglycosides -Immunosuppresants -Cyclosporin -Tacroliumus
Drugs that are occasionally measured
- Digoxin -Theophylline (obstructive airway disease)
- Anti-epileptics- phenytoin, carbamazepine, sodium valproate
What tests do we use to measure these drugs
Warfarin Diuretics, ACE inhibit, NSAIDs Spironolactone Statin Penicillamine
Warfarin- INR Diuretics and Ace inhibit- Renal U&E and potassium NSAIDs- renal U&E Spironolactone- Potassium Statin - LFTs Penicillamine- urine protein
What is lithium used for and why/ how is it monitored
- Bipolar disorder treatment
- Measure sodium for diabetes insipidus
- Measure renal function and TFTs
What antibiotics need monitored and how/ why are they monitored
- Need to measure ahminoglycosides and vancomycin
- Avoid toxicity- renal and auditory nerve
- Tailor dose to ensue therapeutic effect
- Peak and trough levels
Why is drug monitoring important in immunosuppressants
- Enough of a dose to prevent organ rejection but also prevent toxicity
- Immunosuppresants toxic to kidneys so monitor renal function
What is the initial assessment steps for a patient with an overdose
- Assess consciousness - head injury act
- Resp effort and cyanosis
- Cardio exam- pulse and BP
- Neuro exam
- Pupil size and reactivity- opiates
- Suicide assessment
What are the main self harm drugs
- Benzodiazepines
- Tricycylic antidepressants
- Paracetamol
- Aspirin
- Alcohol
Discuss the process of paracetamol toxicity and how it is managed
- Paracetamol converted to toxic metabolite N-acetyle-p-benzoquinonmine (NAPQI) which is normally inactivated by glutathione
- Depleated glutathione in overdose causes NAPQI to bind with sulphur groups on liver membranes causing liver cell necrosis
-Poisoning is 1st asymptomatic, liver failure occurs 72-96 hrs after and may need transplant
Management- measure paracetamol levels at presentation
- Level after 4 hrs- determine if treatment is needed
- Give acetylecysteine (replaces glutathione)
- Give within 8 hrs of overdose
- Increased risk in alcohol abuse, liver enzyme inducing drugs (phenytoin) they will metabolise paracetamol quicker
- Measure INR and creatin9ne
What are the symptoms of aspirin overdose and how is it managed
- Vomiting, sweating, tinnitus , blurred vision, early resp alkalosis then metabolic acidosis later
- Renal failure
Management:
Mild/moderate levels (<600mg/l) oral or IV rehydration and K+ supplements
Severe levels need specific elimination therapy
1. Activated oral charcoal (50g/4hrs) - prevents salicylate absorption
2. Alkalisation 1L 1.26 NaHCO3 over 2 hrs - repeated to keep urine pH >7.5
3. Haemodialysis- levels >1000mg in persistent acidosis or loss of conscious
What are the features and management of ethanol overdose
- Despressed consciousness and hypoglycaemia (esp in children)
- Supportive treatment- monitor fluids and glucose
What is the important thing about Benzodiazepine and tricyclic antidepressant overdose
- No specific treatment and can’t tell exact levels in overdose- only detects if they are present in blood
- Wont indicate if dosage was regular or excessive
- If resp rate falls with benzodiazepines you can give flumazenil
What is the management for lead and iron overdose
Lead= an occupational exposure
-Levels are monitored <4mmol/L -Abdo pain, anaemia, peripheral neuropathy, bone marrow suppression
Treatment: Remove source, chelation therapy, ca EDTA, penicillamine
Iron- emergency
- Abdo pain (gastric erosion) -Nausea -Hypotension -Hepatic injury
- Measure iron levels -Treatment= Chelation with desferrioxamine