GTN (glycerly trinitrate)

Question 1

Presentation

Answer 1

0.3 mg tablet
0.6 mg tablet
Transdermal GTN patch (50 mg 0.4 mg/hr release)

Question 2

Pharmacology

Answer 2

Principally a vascular smooth muscle relaxant

Actions:

• Venous dilatation promotes venous pooling and reduces venous return to the heart (reduces preload)
• Arterial dilation reduces systemic vascular resistance and arterial pressure (reduces afterload)

Effects:

• Reduced myocardial O2 demand
• Reduced systolic, diastolic and MAP BP, while usually still maintaining coronary perfusion pressure
• mild collateral coronary arterial dilatation may improve blood supply to ischaemic areas of myocardium
• mild tachycardia secondary to slight fall in BP
• preterm labour - uterine quiescence in pregnancy

Question 3

Metabolism

Answer 3

By the liver

Question 4

Indications

Answer 4

• Chest pain with ACS
• Acute LVF
• Hypertension associated with ACS
• Autonomic dysreflexia
• Preterm labour (consult)

Question 5

Contras

Answer 5

• known hypersensitivity
• BP < 110 mmHg tablet
• BP < 90 mmHg patch
• Sildenafil Citrate (Viagra) OR Vardenafil (Levitra) in previous 24hrs OR Tadalafil (Cialis) in previous 4 days (PDE5 inhibitors)
• HR > 150 bpm
• HR < 50 bpm (excluding autonomic dysreflexia)
• VT
• Inferior STEMI with BP < 160 mmHg
• Right Ventricular MI

Question 6

Precautions

Answer 6

• No previous administration
• Elderly pts
• Recent MI
• Concurrent use with other tocolytics

Question 7

Route of administration

Answer 7

• SL
• Buccal
• Transdermal
• Infusion (interhospital only)

Question 8

Side effects

Answer 8

• Tachycardia
• Hypotension
• Headache
• Skin flushing (uncommon)
• Bradycardia (occassionally)

Question 9

Special notes

Answer 9

Storage

• susceptible to heat and moisture. Store in original packaging
• do not administer pt’s own medication as it may not have been stored appropriately
• patches should be discarded prior to use-by date
• PDE5 inhibitors can be prescribed to both men and women so ask all pt’s
• Tadalafil (Cialis) may also be prescribed for benign prostatic hypertrophy
• IV infusion may be required for interhospital transfers as per treating doctors orders

Interhospital transfer:

• IV dose prescribed and signed by referring medical officer
• Infusions usually range 5-200 mcg/min, increasing 3-5 mcg/min

Question 10

S/L effects

Answer 10

Onset: 30 secs - 2 mins
Peak: 5-10 mins
Duration: 15-30 mins

Question 11

Intravenous effects

Answer 11

Onset: 30 secs - 1 min
Peak: 3-5 mins
Duration: 15-30 mins

Question 12

Transdermal effect

Answer 12

Onset: Up to 30 mins
Peak: 2 hours

Question 13

ACS with chest pain

Answer 13

Adult
- 600 mcg S/L, repeat @ 5 min titrated to pain or side effects

No prev admin / borderline BP / < 60 kg / elderly / frail
- 300 mcg S/L, repeat @ 5 min titrated to pain or side effects

All pts

• 50 mg patch, upper torso / arms
• remove patch if BP falls < 90 mmHg

Question 14

Pulmonary Oedema (Acute LVF)

Answer 14

SOB + crackles

Adult
- 600 mcg S/L, repeat @ 5 min titrated to pain or side effects

No prev admin / borderline BP / < 60 kg / elderly / frail
- 300 mcg S/L, repeat @ 5 min titrated to pain or side effects

All pts

• 50 mg patch, upper torso / arms
• remove patch if BP falls < 90 mmHg

Question 15

Autonomic Dysreflexia

Answer 15

If systolic BP remains > 160 mmHg after removing the stimulus

Adult
- 600 mcg S/L

No prev admin
- 300 mcg S/L

Repeat initial dose @ 10 min until either:

• symptoms resolve
• onset of side effects
• BP < 160 mmHg

Question 16

Preterm Labour

Answer 16

Birth not imminent < 34 weeks

• consult for 50 mg (0.4mg/hr) patch applied to abdomen
• consult for further 50 mg (0.4mg/hr) patch after 1 hour if contractions persist
• max 20 mg / 24 hr (2 patches)