Wk 3 Toxicology

7/31/2019 Wk 3 Toxicology

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PC 1.3,1.7,1.8 and element 4 session 3


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Study of poisons Any drugs are potential poisons when used

improperly or in excess doses Can be:

Acute

Chronic


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SKIN Rashes

Pruritus

Urticaria

Photosensitivity

GIT Discomfort & pain

Nausea & vomiting

Diarrhoea

Assessment -Assessment - Identifysymptoms


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Assessment -Assessment - Identifysymptoms CARDIOVASCULAR

Abnormalities in cardiac rhythm

Hypotension or hypertension

CCF

Bone marrow depression anaemia

CNS confusion & irritability

Alterations in gait

Tremors


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Assessment -Assessment - Identifysymptoms RENAL

Electrolyte imbalance

Urine retention

Polyuria

Fluid retention RESPIRATORY SYSTEM

Dyspnoea

Asthmatic response

BILIARY SYSTEM Jaundice

Impaired LFTs

Clotting changes


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AssessmentAssessment

Unusual behaviours Vital signs

Baseline T, P, R, BP

CNS symptoms Baseline conscious status alert, orientation

Coma or even death may result from an OD acute or chronic


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AssessmentAssessment

Drug monitoring Blood levels e.g. gentamycin

Therapeutic level Maintained administered at correct time to

optimize blood levels

Individualized dosage Lithium; phenytoin; warfarin

To avoid toxicity Some medications have small safety margin

before toxicity occurs e.g. digoxin


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Four common medications

Paracetamol Analgesic mild pain

Digitalis Cardiac glycoside

Morphine Opiate analgesic severe pain

Warfarin

Anticoagulant


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Toxicity paracetamol

Most common OTC worldwide Most common paediatric accidental exposure 8 grams can be a toxic level i.e. 16 tablets Rapidly absorbed from the small intestine Peak serum concentrations within:

1 2 hours of taking tablet formulation

30 minutes for liquid preparations

20% of ingested paracetamol undergoes 1st pass

metabolism Distribution within 4/24 of ingestion for tablet &

2/24 for liquid


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Half-life 1.5 3 hours General principals of OD

Resuscitation rarely required for an acute OD

Supportive management

Accidental Deliberate

Risk Assessment

Dose taken

Concentration Laboratory report suggestive of liver damage

Serum levels will indicate ifN-acetylcysteine required prevents/reduces liver damage


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Management- single accidental ingestion Children under 6 with observe

Seldom requires any other treatment

Adults 50 gram activated charcoal within 1 2

hours of ingestionTime of ingestion will alter managementType of preparation sustained release has

potential for slow absorption Gastric lavage may be required


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Subsequent management May develop severe hepatotoxicity and liver

failure


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Toxicity digitalis

Symptoms include: EyesBlurred vision, halos around objects

Allergic skin reaction

Hives, rash GITDiarrhoea, loss of appetite, nausea, stomach pain,

vomiting

Cardiac & blood

Irregular heartbeat, weakness Nervous systemConfusion, depression, drowsiness, fainting,

hallucinations, headache, lethargy


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Toxicity digitalis

Symptomatic treatment, may include: Activated charcoal

ECG digitalis depression in the QRS complex

Blood levels for digoxin, magnesium, potassium

Correction of electrolyte imbalances

Breathing support

Dialysis

Gastric lavage


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Toxicity morphine

Long term use patient tolerance increases Overdose symptoms:

Cyanosis - fingernails & lips

Cold, clammy skin

Constipation

Convulsions

Dizziness, fainting

Itching skin

Slow, shallow respiration rate

BP

Weak pulse


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Toxicity morphine

Overdose symptoms ctd: Muscle spasms

Sedation

Skeletal muscle flaccidity

Pinpoint pupils

Coma

IF patient is Comatose, has pinpoint pupils & shallow, short,

respirations or has stopped breathing requiresCPR and narcain ASAP to reverse effect onrespiratory system


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Toxicity morphine

Other drugs that affect morphine include: Sedatives

Tranquillizers

Muscle relaxants

May increase the side effects of morphine


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Toxicity warfarin

Anticoagulant Reduces the prothrombin (PT) i.e. the time it

takes the blood to clot

Commonly used to treat blood clots due tovarious causes Most important effect of warfarin OD is

bleeding

Nosebleeds, bright blood in stools, vomiting, easybruising, cuts take longer to stop bleeding

Antidote Vitamin K


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Toxicity warfarin

Patients on long term therapy requiremonitoring

INR (International Normalized Ratio) 2.0 - 3.0desirable range (2.5 optimal)

Patient may be on medication 6/52 6/12 Patients > 75 at greater risk of intracranial

bleeding when taking warfarin so the INR

target level usually reduced & can be as lowas 1.5 2.0


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Toxicity warfarin

Factors that effect dosage include: Old age, reduced body weight, impaired cardiac

function, impaired liver function

Drug interactions that can prolong the

PT e.g. Allopurinol

Chloramphenacol

Cimetidine

Ciprofloxacin

Metronidazole

tamoxifen


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Toxicity warfarin

Drug interactions that can interferewith protein binding e.g. Chloral hydrate; salicylates

Drug interactions that can reduce PT by

decreasing the effect of warfarin e.g. Inhibition of warfarin absorptionAluminum hydroxide; colestipol

Enhanced warfarin metabolismBarbiturates; phenytoin

Promote Vitamin K activityFoods with high Vitamin K content (>200 mcg) e.g.

brussel sprouts; chick peas; parsley; red leaf lettuce


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Toxicity warfarin

Emergency Treatment includes: Activated charcoal Baseline PT/INR

Blood transfusion if significant blood loss May require transfusion of clotting factors II,

VII, IX & X Vitamin K used if evidence of anticoagulation

exists. Dose varies with clinical situation,amount taken type i.e. short or long acting

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Wk 3 Toxicology