Migraine

Question 1

Gabapentin and pregabalin

Common indications

Answer 1

1. Both drugs are used for focal epilepsies (with or without secondary generalisation), usually as an add-on treatment when other anti-epileptic drugs (e.g. CBZ) provide inadequate control
2. Both drugs are used for neuropathic pain. Pregabalin in particular is recommeded as a 2nd line option in painful diabetic neuropathy (alternate to duloxetine) and as a first line option in other painful neuropathies
3. Gabapentin can be used in migraine prophylaxis
4. Pregabalin is used in GAD

Question 2

Gabapentin and pregabalin

MOA

Answer 2

• Gabapentin + pregabalin are closely related to GABA, the major inhibitory neurotransmitter in the brain. However MOA is unrelated to GABA
• It binds to voltage-sensitive Ca2+ channels, where it presumably prevents inflow of Ca and in doing so prevents release of neurotransmitter
• This interferes with synaptic transmission and reduces neuronal excitability

Question 3

Gabapentin and pregabalin

Adverse effects

Answer 3

• Gabapentin and pregabalin are generally better tolerated than other antiepiletic drugs.
• Their main side effects are drowsiness, dizzieness and ataxia, which usually improve over the first few weeks of treatment

Question 4

Gabapentin and pregabalin

Warnings

Answer 4

• Both drugs depend on the kidneys for their elimination, so their doses should be reduced in renal impairment

Question 5

Gabapentin and pregabalin

Important interactions

Answer 5

• The sedative effects of gabapentin and pregabalin may be enahanced when combined with other sedating drugs (e.g. BZ)
• Other than this, gabapentin and pregabalin are notable in having relatively few drug interactions- in stark contrast to most other antiepileptic drugs
• This makes them particularly useful where combination regimens are considered necessary

Question 6

Gabapentin and pregabalin

Communication

Answer 6

• Explain that you are offering a medicine which you anticipate will reduce the severity of the symptoms (frequency of fits)
• Explain that the medicine commonly causes some drowsiness or dizziness
• For this reason, you will prescribe a low dose initially, then increase this gradually (make sure they are clear on the dosing instructions)
• Explain that these side effects should improve over the first few weeks
• They should avoid driving until they are confident that the symptoms have settled

Question 7

Clonidine

Indications

Answer 7

• HTN
• Prevention of migraine
• Prevention of headache
• Prevention of menopausal symptoms (Flushing/Vasomotor condition)

Question 8

Clonidine

MOA

Answer 8

• Anti-HTN- Centrally acting alpha2-adrenoreceptors, reducing sympathetic tone, resulting in a fall in diastolic and systolic BP and HR
• Reduces responsiveness of peripheral vessels to constrictor and dilator stimuli, thereby preventing the vascular changes associated with migraine
• The same direct action on peripheral vessels moderates the vascular changes associated with menopausal flushing

Question 9

Clonidine

Adverse effects

Answer 9

• Postural hypotension, Dizziness
• Depression
• Sedation
• Dry mouth
• Fatigue
• headache

Question 10

Clonidine

Warnings

Answer 10

• Contraindicated in
  
  • Severe bradyarrhythmia, AV block
• Cautions
  
  • Constipation
  • HF
  • Depression
  • Raynauds
  • Elderly- STOPP criteria

Question 11

Clonidine

Interactions

Answer 11

• Anything that can increase the hypotensive effect
• Mirtazapine- also inhibits a2-adrenoreceptors
• Use of BB/digoxin- increased risk of bradycardia
• Orthostatic hypotension may be provoked or aggravated by concomitant administration of TCA. NB- TCA can also antagonise clonidine
  *

Question 12

Clonidine

Monitoring

Answer 12

• BP- Including postural/orthostatic
• HR