midodrine

see also:

• alpha adrenergic agonists
• sympathomimetics
• Autonomic dysfunction and autonomic neuropathy

• midodrine is a pro-drug of desglymidodrine which is a peripherally active, selective, alpha adrenergic 1 agonist which is primarily used for the Rx of symptomatic Autonomic dysfunction and autonomic neuropathy|dysautonomia and postural hypotension]] as a result of its widespread vasoconstriction actions
• unlike most sympathomimetics, it does not act on beta adrenergic receptors and does not usually produce the usual tachycardia

• symptomatic Autonomic dysfunction and autonomic neuropathy|dysautonomia and postural hypotension]] where other treatments have failed
• refractory recurrent vasovagal syncope / neurocardiogenic syncope
• dialysis associated hypotension

• urinary retention risk / benign prostatic hyperplasia (BPH)
• hypertension
• phaeochromocytoma
• severe heart disease
• hyperthyroidism
• orthostatic hypotension in diabetics
• hepatic insufficiency
• known hypersensitivity
• children, pregnancy and lactation - safety data not available

• midodrine 2.5-10mg orally tds given 3-4hrly during waking hours when likely to be upright and not after evening meal or within 4hrs of bedtime - maximum daily dose is 30-40mg
• may need to adjust dose in renal impairment

• desglymidodrine concentration peaks at 1hr post-dose and has a half life of 3hrs being mainly renally excreted

• supine hypertension
• reflex bradycardia
• tachyarrhythmias
• urinary retention
• raised intra-ocular pressure esp. if vision problems and on fludrocortisone
• toxicity if renal impairment

• severe hypertension which may cause:
  • reflex bradycardia
  • stroke (CVA) / intracranial haemorrhage
  • acute coronary syndromes
  • aortic dissection
  • acute pulmonary oedema (APO)
  • encephalopathy
• urinary retention may occur
• piloerection
• rarely, may cause profound cardiovascular collapse and the shocked hypotensive patient

• usual ABC's
• ECG and cardiac monitoring
• bloods for co-ingestions as per usual overdoses (eg. ethanol, paracetamol)
• if altered conscious state, CT scan to exclude intracranial haemorrhage
• if normal conscious state and likely ingestion of more than 2mg/kg within the last hour, consider activated charcoal
• Rx hypertension - options:
  • nitrates
  • iv labetalol
  • iv phentolamine
• Rx hypotension caused by bradycardia
  • iv atropine
• bladder scan to check for acute urinary retention and Rx with IDC as indicated
• observe for at least 6hrs after significant overdose
• consider discussing with clinical toxicologist if significant overdose as limited experience to date