EMT Pharmacology

What is Adrenaline Mechanism of Action?

• Adrenaline stimulates alpha and beta receptors, with the predominant effects occurring at alpha 1, beta 1 and beta 2 receptors.

• Alpha 1 stimulation causes smooth muscle contraction, vasoconstriction of blood vessels and stimulation of glycogenolysis and gluconeogenesis.

• Beta 1 stimulation causes an increase in inotropy (cardiac contractility), an increase in chronotropy (heart rate) and an increase in dromotropy (speed of electrical conduction within the heart).

• Beta 2 stimulation causes smooth muscle relaxation, skeletal muscle vasodilation, bronchodilation, and stabilisation of mast cell membranes, reducing histamine release.

Adrenaline Medication Indications:

• Anaphylaxis.

• Severe asthma.

• Imminent respiratory arrest from COPD. 

• Stridor causing moderate or severe respiratory distress. 

• IN for clinically significant epistaxis. 

• Topical for clinically significant bleeding from a wound.

Adrenaline Medication Contraindications:

None

Adrenaline Medication Cautions:

• Myocardial ischaemia. Adrenaline will increase myocardial oxygen consumption.

• Tachydysrhythmias. Adrenaline will usually make tachydysrhythmias worse.

EMT Adrenaline Administration

• Topical: dilute each mg of adrenaline to a total of 10ml using 0.9% NaCl. This solution is 1:10,000 and contains 0.1mg/ml. Apply topically in addition to direct pressure.

• IN: dilute each mg of adrenaline to a total of 10ml using 0.9% NaCl. This solution is 1:10,000 and contains 0.1 mg/ml. Administer the appropriate dose into each bleeding nostril using a mucosal atomising device, in addition to direct pressure.

• Nebulised: 5mg administer undiluted.

• IM: 0.5mg undiluted. The preferred IM site is the lateral thigh. If this site is not suitable use the lateral upper arm.

Adrenaline Dosage for Anaphylaxis

Adults: 0.5mg adrenaline IM

Child: peads. Drug dose tables

• repeat every 10mins if patient isn’t improving

• repeat every 5mins if patient is deteriorating

Adrenaline Dosage for Asthma

In severe asthma that aren’t improving after initial nebulised bronchodilators (salbutamol and ipratropium).

            Adult: 0.5mg adrenaline IM

            Child: peads. Drug dose tables

           *repeat every 10mins if deteriorating and no IV adrenaline is being given.

Adrenaline Dosage for Stridor

5mg nebulised adrenaline if stridor causing mod.-severe respiratory distress

            *repeat every 10mins as required

Adrenaline Dosage for Epistaxis

• 0.2mg (2 ml of 1:10,000) per bleeding nostril for a patient aged ≥12yrs.

• 0.1mg (1 ml of 1:10,000) per bleeding nostril for a child aged 5-11 years.

• Seek clinical advice if the patient is a child aged <5yrs. 

*repeat once after 20mins if the bleeding does not stop or recurs and TXA is not available.

Adrenaline Dosage for Wound Bleeding

Dilute adrenaline to 1:10,000 using 0.9% of sodium chloride.

Soak a dressing in 1:10,000 adrenaline. Place the dressing into the wound or over the bleeding site, and continue to provide pressure over the wound.

Common Adverse Effects of Adrenaline Medication:

• Tachycardia.

• Tachydysrhythmia.

• Myocardial ischaemia.

• Ventricular ectopy.

• Hypertension.

• Nausea and vomiting.

• Tremor, anxiety and sweating.

• Hyperglycaemia.

Usual Onset of Effect Adrenaline Medication:

• IM: 2-5 minutes.

• Nebulised, IN and topical: on contact with the target site.

Usual Duration of Effect Adrenaline Medication:

• The cardiovascular effects last 5-15 minutes.

• The mast cell membrane effects may last for several hours.

Usual Preparation of Adrenaline Medication:

Ampoule containing 1mg in 1ml

What is the Mechanism of Action of Aspirin?

• Aspirin (acetylsalicylic acid) has antiplatelet, antipyretic, anti-inflammatory and analgesic effects. In the out-of-hospital setting aspirin is only administered for its antiplatelet activity.

• Aspirin inhibits the enzyme cyclooxygenase which results in a reduction in the formation of prostaglandins and thromboxane.

Aspirin Medication Indications:

• Myocardial ischaemia

• STEMI

Aspirin Medication Contraindications:

• Known severe allergy.

• Third trimester of pregnancy.

Aspirin Medication Cautions:

• Known bleeding disorder. Aspirin will increase the risk of bleeding, however the balance of risk is usually in favour of administering aspirin. 

• Clinically significant bleeding. Aspirin will increase the risk of bleeding and the nature and risk of the bleeding must be taken into account. 

• Known worsening of bronchospasm with NSAIDs. Some patients with asthma or COPD have known worsening of bronchospasm with NSAIDs (including aspirin) and a decision must be made based on the balance of risk. If there is a clear history of significant bronchospasm with NSAIDs, aspirin should be withheld.

Aspirin Medication Dosage:

300mg

Aspirin Medication Administration:

Administer PO. Dispersible tablets may be chewed or dissolved in water.

Aspirin Medication Common Adverse Effects:

• Increased bleeding.

• Although indigestion, gastrointestinal ulceration and gastrointestinal bleeding are commonly listed as adverse effects, these are only associated with long-term administration.

Aspirin Medication Usual Onset of Effects:

30 - 60 mins

Aspirin Medication Usual Duration of Effects:

3-5 days for the antiplatelet activity. This is because platelets exposed to aspirin are impaired for the life of the platelet which is 7-10 days. Approximately 10% of platelets are replaced each day.

Aspirin Medication Usual Preparation:

300 mg dispersible tablets.

If patient has taken aspirin?

• If the patient still has the tablets in their mouth, ask them to spit the tablets out and administer an additional 300 mg of dispersible aspirin.

• If the patient has chewed and swallowed 300 mg of aspirin (including enteric coated aspirin), do not administer additional aspirin.

• If the patient has swallowed (without chewing) 300 mg of enteric coated aspirin, administer an additional 300 mg of dispersible aspirin. This is because absorption of the enteric coated aspirin will be delayed.

• If it is unclear what the patient has taken, administer an additional 300 mg of dispersible aspirin. 

What is Glucagon Medication Mechanism of Action:

Glucagon increases the blood glucose level by stimulating glycogenolysis (the breakdown of glycogen into glucose), predominantly within the liver.

Glucagon Medication Indications:

Hypoglycaemia when the patient cannot safely swallow glucose/food and IV access cannot be obtained.

Glucagon Medication Contraindications:

Known severe allergy

Glucagon Medication Cautions:

None

Glucagon Medication Dosage:

• 1 mg IM once for an adult or child aged greater than or equal to five years.

• 0.5 mg IM once for a child aged less than five years.

Glucagon Medication Administration:

• Dissolve the powder using the syringe within the kit and administer IM.

• The preferred site is the lateral thigh as this has the best absorption. If this site is not suitable use the lateral upper arm.

Glucagon Medication Common Adverse Effects:

None

Glucagon Medication Usual Onset of Effect:

5 - 10 mins

Glucagon Medication Usual Duration of Effect:

15 - 60 mins

Glucagon Medication Preparation:

Ampoule containing 1mg as powder.

• Glucagon relies on stored glycogen being available to exert its effect and if glycogen stores are not available, glucagon may be ineffective. Examples include if the patient:

• Does not have diabetes.

• Has sepsis.

• Is a young child.

• Has undergone strenuous exercise.

• Has not eaten food for more than 12 hours.

• Is suffering from adrenal insufficiency.

• Is suffering from chronic hypoglycaemia.

• Is suffering from alcohol-induced hypoglycaemia.

What is the Mechanism of Action of Glucose Gel?

Glucose gel provides a source of glucose that can be easily swallowed and is rapidly absorbed.

Glucose Gel Indications:

• Hypoglycaemia in adults and children provided the patient is conscious enough to be able to swallow safely.

• Hypoglycaemia in neonates.

Glucose Gel Contraindications:

None

Glucose Gel Cautions:

None

Glucose Gel Dosage:

• 10-20 g for all ages.

• Administer one sachet and repeat every ten minutes if hypoglycaemia persists or recurs.

Glucose Gel Common Adverse Effects:

None

Glucose Gel Usual Onset of Effects:

5 - 10 mins

Glucose Gel Usual Duration of Effects:

30 - 60 mins

Glucose Gel Usual Preparation:

• There are multiple different brands.

• Most are a sachet containing 10-20 g glucose.

What is the Mechanism of Action of GTN (Glyceryl Trinitrate) Spray:

• GTN is a vasodilator. It acts on vascular smooth muscle to cause venous and arterial vasodilation, with the predominant effect being on veins.

• The mechanism of action is not clear, but it appears that GTN results in the formation of nitric oxide which is a vasodilator. GTN causes: 

  • A reduction in venous return (preload) to the heart. This reduces ventricular filling and cardiac output which reduces myocardial oxygen demand.

  • Arterial dilation which reduces peripheral resistance (afterload). This reduces the force the left ventricle must overcome to eject blood into the arteries which reduces myocardial oxygen demand.

  • Dilation of the coronary arteries which may increase coronary blood supply, though this is not usually clinically significant.

GTN (Glyceryl Trinitrate) Spray Indications:

• Myocardial ischaemia.

• Cardiogenic pulmonary oedema.

• Control of hypertension associated with autonomic dysreflexia.

• STEMI

GTN (Glyceryl Trinitrate) Spray Contraindications:

• Known severe allergy.

• Systolic BP less than 110 mmHg. 

• Heart rate less than 40/minute. 

• Heart rate greater than 150/minute. 

• Ventricular tachycardia.

GTN (Glyceryl Trinitrate) Spray Cautions:

• STEMI, particularly STEMI involving the RV. GTN may cause a significant fall in cardiac output and if there are signs of low cardiac output GTN should be withheld. 

• The patient is frail. 

• Signs of shock. The patient’s reduced cardiac output may fall further with GTN administration. 

• Dysrhythmia. This may cause a reduced cardiac output which may fall further with GTN administration. 

• Has taken a phosphodiesterase inhibitor in the last 24 hours. See common interactions. 

• Known aortic or mitral stenosis. With aortic or mitral stenosis, cardiac output may be reduced as a result of the narrowed valve and a fall in preload may cause a further fall in cardiac output.

GTN (Glyceryl Trinitrate) Spray Dosage:

• Myocardial ischaemia: 0.4mg every 5mins. Consider increasing the dosing interval to 10minutes if a caution is present. 

• STEMI: 0.4mg with caution. Withhold if signs of poor perfusion are present. 

• Cardiogenic pulmonary oedema: 0.8mg every 5mins Consider increasing the dosing interval to ten minutes if a caution is present. Increase the dose and frequency if the patient is not improving.

• Control of hypertension: 0.4mg every 5mins.

GTN (Glyceryl Trinitrate) Spray Administration:

• Spray under the tongue. If this cannot be achieved it is acceptable to spray into the mouth. 

• If GTN is administered in the presence of a caution: 

  • The patient should be lying flat. 

  • IV access should have been obtained whenever possible. 

  • The dosing interval should be increased to ten minutes. 

  • Be ready to administer 0.9% NaCl IV if there is a significant fall in cardiac output or blood pressure.

GTN (Glyceryl Trinitrate) Spray Common Adverse Effects:

• Hypotension.

• Flushing.

• Headache.

• Tachycardia.

• Feeling light-headed.

GTN (Glyceryl Trinitrate) Spray Usual Onset of Effect:

1 - 2 mins

GTN (Glyceryl Trinitrate) Spray Usual Duration of Effect:

15 - 30 mins

GTN (Glyceryl Trinitrate) Spray Usual Preparation:

Metered dose bottle delivering 0.4 mg doses.

What is the Mechanism of Action of Ibuprofen?

• Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) that is predominantly used for treating pain. 

• Ibuprofen inhibits the activity of the enzyme prostaglandin synthetase, reducing prostaglandin production and causing a reduction in inflammation, pain and fever. 

Ibuprofen Indications: 

• Mild to moderate pain, usually in combination with paracetamol. 

• Moderate to severe pain, usually in combination with other medicines.

Ibuprofen Contraindications: 

• Known severe allergy. 

• Pregnancy. 

• The presence of sepsis, dehydration, shock or clinically significant bleeding. Ibuprofen can worsen renal impairment and increase the risk of bleeding. 

• Known worsening of bronchospasm with NSAIDs. Some patients with asthma or COPD have known worsening of bronchospasm with NSAIDs. If there is a clear history of significant bronchospasm with NSAIDs, ibuprofen must not be administered.

Ibuprofen Cautions: 

• The patient has taken ibuprofen within the last 4 hours. 

• Abdominal pain, particularly if the patient is very unwell or vomiting.  

• Age greater than or equal to 75 years, particularly if frail. In this setting, renal impairment is likely and ibuprofen may worsen renal impairment.

Ibuprofen Dosage:

• 600 mg for an adult weighing greater than 80 kg.

• 400 mg for an adult weighing 80 kg or less. 

• See the paediatric drug dose tables for a child.

Ibuprofen Administration:

• Administer PO. 

• Children unable to swallow tablets may be administered ibuprofen syrup, or tablets that have been crushed and placed in a soft food such as jam or honey

Ibuprofen Common Adverse Effects:

• Renal impairment. 

• Increased bleeding. 

• Although indigestion, gastrointestinal ulceration and gastrointestinal bleeding are commonly listed as adverse effects, these are only associated with chronic administration.

Ibuprofen Usual Onset of Effects:

30 - 60 mins

Ibuprofen Usual Duration of Effects:

4 - 6 hours

Ibuprofen Usual Preparation:

• 200 mg tablets. 

• Syrup containing 20 mg/ml.

What is the Mechanism of Action of Ipratropium?

• Ipratropium is a bronchodilator.

• Ipratropium is an anticholinergic agent with predominantly antimuscarinic activity. It antagonises (blocks) acetylcholine receptors, causing vagal inhibition resulting in bronchodilation.

Ipratropium Indications:

• Bronchospasm secondary to asthma or COPD. 

• Prominent bronchospasm secondary to airway burns, smoke inhalation or chest infection.

Ipratropium Contraindications:

Known severe allergy

Ipratropium Cautions:

None

Ipratropium Dosage:

0.5 mg for adults and children once only.

Ipratropium Administration:

Administer nebulised undiluted (in combination with 5mg of salbutamol) using: 

• Air as the driving gas for COPD. 

• Oxygen as the driving gas for asthma.

Ipratropium Common Adverse Effects:

• Tachycardia.

• Dry mouth.

• Blurred vision. This usually only occurs with repeated doses.

Ipratropium Usual Onset of Effects:

2 - 5 mins

Ipratropium Usual Duration of Effects:

6 hours

Ipratropium Usual Preparation:

Ampoule containing 0.5mg in 2ml

What is the Mechanism of Action of Loratadine?

• Loratadine is a non-sedating antihistamine.

• Loratadine antagonises (blocks) peripheral histamine receptors, blocking the action of histamine and reducing itching and redness.

Loratadine Indications:

• Minor allergic reactions confined to skin involvement.

• Itch or rash associated with anaphylaxis, provided all systemic signs of anaphylaxis are improving.

Loratadine Contraindications:

• Known severe allergy.

• Age less than one year.

Loratadine Cautions:

Pregnancy

Loratadine Dosage:

• 20 mg for an adult or child aged greater than or equal to 12 years.

• 10 mg for a child aged 1-11 years.

Loratadine Administration:

• Administer PO.

• Always ask a parent (or guardian) if a young child can swallow tablets. Loratadine may be crushed and placed in a soft food such as jam or honey.

Loratadine Common Adverse Effects:

None

Loratadine Usual Onset of Effects:

30 - 60 mins

Loratadine Usual Duration of Effects:

12 - 24 hours

Loratadine Usual Preparation:

10mg tablets

What is the Mechanism of Action of Methoxyflurane?

• Methoxyflurane is an inhalational analgesic. 

• The mechanism of action is not clear.

Methoxyflurane Indications:

Moderate to severe pain, when there will be a significant delay in an opiate being administered.

Methoxyflurane Contraindications:

• Known severe allergy. 

• Personal or family history of malignant hyperthermia. 

• Known renal impairment.

• Methoxyflurane administered within the last week. Frequent administration increases the risk of renal impairment.

Methoxyflurane Cautions:

• Age greater than or equal to 75 years, particularly if frail.

• Pre-eclampsia. In this setting, renal impairment is likely and methoxyflurane may worsen renal impairment. 

• Administration within a confined space.

• Acute exacerbation of chronic pain.

Methoxyflurane Dosage:

• Maximum of 6 ml (two doses) for a patient aged greater than or equal to 12 years. 

• Maximum of 3 ml (one dose) for a child aged less than 12 years. 

Methoxyflurane Administration:

• Whenever possible, have the patient self-administer methoxyflurane.

• Administer 3 ml (one dose) at a time and always use the charcoal filter. Using a charcoal filter maximises the amount of exhaled methoxyflurane that is absorbed, limiting exposure to personnel. 

• Instruct the patient to breathe out through the inhaler. 

• Do not administer supplementary oxygen via the inhaler as this significantly increases the amount of methoxyflurane lost through evaporation.

• Place the inhaler in a closed plastic bag if the methoxyflurane has not been fully used. It may subsequently be reused by the same patient.

• An ambulance is not considered a confined space. Maximising ventilation (for example, having ventilation fans on) reduces occupational exposure. Consider not administering methoxyflurane in an ambulance if the patient cannot cooperate with breathing out through the inhaler.

Methoxyflurane Common Adverse Effects:

• Sedation

• Light-headed

• Bad taste

Methoxyflurane Usual Onset of Effect:

1 - 2 mins

Methoxyflurane Usual Duration of Effect:

2 - 5 mins after stopping administration

Methoxyflurane Usual Preparation:

3 ml bottle accompanying a plastic inhaler.

Is methoxy cautioned/contraindicated for Renal failure with dialysis, Kidney stones and/or renal colic?

No

What is the Mechanism of Action of Ondansetron?

• Ondansetron is an antiemetic.

• Ondansetron antagonises (blocks) serotonin receptors centrally in the brain and peripherally in the gastrointestinal tract, resulting in a reduction in nausea and vomiting.

Ondansetron Indications:

Clinically significant nausea and/or vomiting.

Ondansetron Contraindications:

• Known severe allergy.

• Age less than one year.

• Suspected serotonin syndrome.

Ondansetron Cautions:

None