Pharmacology

Question 1

What are the features of cocaine toxicity and how is it managed?

Answer 1

MOA:
- Blocks uptake of dopamine, noradrenaline and serotonin

Adverse effects:
CARDIO - coronary artery spasms, htn, QRS/QT prolong, aortic dissection
NEURO - seizures, mydriasis, hyperreflexia, hypertonia
PSYCH - agitation, psychosis, hallucinations
OTHER - ischaemic colitis if ingested, hyperthermia, metabolic acidosis, rhabdo

Management:
1. Chest pain - benzo + GTN
2. Hypertension - benzo + sodium nitroprusside

Question 2

What are the features of ecstasy poisoning and how is it managed?

Answer 2

Features:
CARDIO - tachycardia, htn
NEURO - agitation, anxiety, ataxia
OTHER - hyponatremia, hyperthermia, rhabdo

Management:
Supportive +/- dantrolene for hyperthermia

Question 3

What drugs are used in alcohol problem drinking?

Answer 3

Acute withdrawal - chlordiazepoxide

Promoting abstinence - disulfram (reaction when mixed with alcohol)

Reducing craving - acamprosate

Question 4

How is paracetamol overdose managed?

Answer 4

• Activated charcoal if ingested <1h ago
• Otherwise blood test +/- NAC after 4h
• Commence NAC without bloods if staggered OD
• Commence NAC without bloods if 8-24h
• Liver transplant (if pH<7.3 24h after ingestion or all of PT >100, creat >300, grade III/IV encephalopathy)

NAC is infused over 1h

Question 5

How does salicylate overdose (aspirin) present and how is it managed?

Answer 5

Features:
- Hyperventilation
- Tinnitus
- Mixed respiratory alkalosis and metabolic acidosis

Management:
- ABC
- Urinary alkalinization with IV bicarbonate
- Haemodialysis

Question 6

How is benzodiazepine overdose managed?

Answer 6

• Supportive care
• Flumazenil if severe (but risk of seizure)

Question 7

How is TCA overdose managed?

Answer 7

• IV bicarbonate to reduce the risk of seizureas and arrhythmias
• AVOID NORMAL ANTIARRHYTHMICS

Question 8

How is lithium toxicity managed?

Answer 8

Presents as coarse tremor, hyperreflexia, confusion, polyuria, seizure, coma

Precipitants:
- Dehydration and renal failure
- Drugs (diuretics esp thiazides, ACEi/ARBs, NSAIDs, metronidazole)

Management:
- Mild to moderate: IV saline
- Consider sodium bicarbonate
- Severe: haemodialysis

Question 9

How is beta-blocker overdose managed?

Answer 9

• Give atropine if bradycardia
• Give glucagon if refractory

Question 10

How is ethylene glycol poisoning managed?

Answer 10

• Fomepizole (works by inhibitingalcohol dehydrogenase)
• Haemodialysis if refractory

(ethylene glycol is found in hydraulic brake fluid, solvents, paints)

Question 11

How is methanol poisoning managed?

Answer 11

• Fomepizole
• Haemodialysis

Question 12

How does organophosphate insecticide poisoning present and how is it managed?

Answer 12

Features:
SLUD - salivation, lacrimuation, urination, defecation
Hypotension and bradycardia
Miosis and muscle fasciculations

Management:
- Atropine

Question 13

How does digoxin work and how is toxicity managed?

Answer 13

MOA:
- Cardiac glycoside used in rate control in AF management
- Decreases conduction through the AV node to decrease ventricular rate, and increases cardiac muscle contraction
- No routine monitoring

Toxicity:
- Measure concentrations 8-12 hours after last dose
- Presents as yellow vision, confusion, arrhythmias, gynaecomastia
- Precipitated by hypokalemia
- Manage with DIGIBIND (Digoxin-specific antibody fragments) and correct arrhythmias

Question 14

How is iron poisoning managed?

Answer 14

• Dexferrioxamine (chelating agent)

Question 15

How is lead poisoning managed?

Answer 15

• Dimercaprol or calcium edetate

Question 16

What are the features of carbon monoxide poisoning and how is it managed?

Answer 16

Features:
- Carbon monoxide has high affinity for Hb causing left shift of oxygen dissociation curve and tissue hypoxia
- Presents as headache, N&V, pink mucosa
- >3% carboxyHb or >10% in smokers

Management:
- 100% high flow oxygen ASAP for minimum of 6 hours
- Hyperbaric oxygen

Question 17

How is cyanide poisoning managed?

Answer 17

• Hydroxycobalamin
• Can also give combination of amyl nitrite, sodium nitrite and sodium thiosulfate

Question 18

How does amiodarone cause thyroid dysfunction?

Answer 18

1. Hypothyroidism
   - Due to high iodine content of amiodarone causing an autoregulary effect by inhibiting thyroxine formation
2. Thyrotoxicosis type 1
   - Excess iodine-induced thyroid hormone synthesis with goitre formation
   - Manage with carbimazole or potassium perchlorate
3. Thyrotoxicosis type 2
   - Destructive thyroiditis
   - Manage with steroids

Question 19

What are the side effects and contraindications of phosphodiesterase V inhibitors (PDE5)?

Answer 19

eg. sildenafil

Side effects:
- Visual disturbance (blue discolouration), AIN
- Nasal congestion and headache
- Flushing
- GI side effects

Contraindications:
- Pts on nitrates and realted drugs eg. nicoranidl
- Hypotension
- Recent stroke or MI (wait 6 months)

Question 20

What are the adverse effects and interactions of allopurinol?

Answer 20

Adverse effects:
DERM! (should stop immediately if develop a rash) - SCAR, DRESS, SJS

Interactions:
- Azathioprine; should reduce dose
- Cyclophosphamide; may cause marrow toxicity
- Theophylline; inhibits breakdown

Question 21

Which drugs cause urinary retention?

Answer 21

• Opiates
• Anticholinergics eg. antipsychotics/antihistamines
• Tricyclic antidepressants
• NSAIDs
• Disopyramide

Question 22

Which drugs cause lung fibrosis?

Answer 22

• Amiodarone
• RA drugs (methotrexate, sulfasalazine, gold)
• Cytotoxic agents (busulphan, bleomycin)
• Nitrofurantoin
• Dopamine agonists (bromocriptine, cabergoline, pergolide)

Question 23

How do you manage opiod overdose and dependence?

Answer 23

Overdose:
- Naloxone

Dependence:
- Methadone or buprenorphine
- Monitor compliance with urinalysis
- Should last 4 weeks in IP setting or 12 weeks in the community