Milrinone
CLASS
- bipyridine
MECHANISM OF ACTION
- non receptor mediated inhibitor of cAMP phosphodiesterase III isoenzyme -> decrease the hydrolysis of cAMP
- increase cAMP (analogous to activating a Gs protein)
-> increase in adenyl cyclase
-> increase protein kinases
-> increased phosphorylation of proteins
-> net influx of Ca2+ into muscle
-> ‘inodilator’
-> inotropy
-> vascular and bronchial muscle relaxation
- inotropy + decreased SVR -> increased SV -> increased Q
- effective in patients on b-blockers and with b-adrenoceptor downregulation (as occurs in chronic CHF)
- less increase in myocardial O2 consumption and tachycardia than b-agonists, with lower filling pressures and lower pulmonary vascular resistance (PVR)
- titratable infusion, unlike levosimendan which has long duration of action
PHARMACEUTICS
- 1mg/mL vials
- dilute
- use within 24 hrs
DOSE
- loading dose 50mcg/kg
- infusion 0.375-0.75mcg/kg/min
INDICATION
- low cardiac output states (considered first line by some, rarely used by others)
ADVERSE EFFECTS
- hypotension -> consider adding noradrenaline
- bronchospasm (edit: really?)
- arrhythmias (rare, less tachycardia than b-agonists)
- thrombocytopaenia
- hepatic dysfunction
PHARMACOKINETICS
- Distribution – Vd 0.38L/kg, 70% protein bound
- Metabolism – minimal
- Elimination – t1/2 = 2.3 hrs, action ceases 8 hours post termination of infusion, renal elimination -> prolongs half life
EVIDENCE
- more successful weaning from bypass (proven in a small (n ~50) RCT vs placebo – 100% vs 33%)
Warrilow’s ‘case for milrinone’:
- inodilator
- effective in patient receiving beta blockers or with down regulation of cardiac adrenoreceptors (chronic cardiac failure)
- less tachyarrhythmias than b-agonists
- pulmonary vasodilator
- hypotension due to vasodilation (often needs noradrenaline, which also has some mild b-agonism)
- relatively cheap in short term
References and Links
CCC Pharmacology Series
Respiratory: Bosentan, Delivery of B2 Agonists in Intubated Patients, Nitric Oxide, Oxygen, Prostacyclin, Sildenafil
Cardiovascular: Adenosine, Adrenaline (Epinephrine), Amiodarone, Classification of Vasoactive drugs, Clevidipine, Digoxin, Dobutamine, Dopamine, Levosimendan, Levosimendan vs Dobutamine, Milrinone, Noradrenaline, Phenylephrine, Sodium Nitroprusside (SNiP), Sotalol, Vasopressin
Neurological: Dexmedetomidine, Ketamine, Levetiracetam, Lignocaine, Lithium, Midazolam, Physostigmine, Propofol, Sodium Valproate, Sugammadex, Thiopentone
Endocrine: Desmopressin, Glucagon Therapy, Medications and Thyroid Function
Gastrointestinal: Octreotide, Omeprazole, Ranitidine, Sucralfate, Terlipressin
Genitourinary: Furosemide, Mannitol, Spironolactone
Haematological: Activated Protein C, Alteplase, Aprotinin, Aspirin, Clopidogrel, Dipyridamole, DOACs, Factor VIIa, Heparin, LMW Heparin, Protamine, Prothrombinex, Tenecteplase, Tirofiban, Tranexamic Acid (TXA), Warfarin
Antimicrobial: Antimicrobial Dosing and Kill Characteristics, Benzylpenicillin, Ceftriaxone, Ciprofloxacin, Co-trimoxazole / Bactrim, Fluconazole, Gentamicin, Imipenem, Linezolid, Meropenem, Piperacillin-Tazobactam, Rifampicin, Vancomycin
Analgesic: Alfentanil, Celecoxib, COX II Inhibitors, Ketamine, Lignocaine, Morphine, NSAIDs, Opioids, Paracetamol (Acetaminophen), Paracetamol in Critical Illness, Tramadol
Miscellaneous: Activated Charcoal, Adverse Drug Reactions, Alkali Therapies, Drug Absorption in Critical Illness, Drug Infusion Doses, Epidural Complications, Epidural vs Opioids in Rib Fractures, Magnesium, Methylene Blue, Pharmacology and Critical Illness, PK and Obesity, PK and ECMO, Sodium Bicarbonate Use, Statins in Critical Illness, Therapeutic Drug Monitoring, Weights in Pharmacology
Toxicology: Digibind, Flumazenil, Glucagon Therapy, Intralipid, N-Acetylcysteine, Naloxone, Propofol Infusion Syndrome
- Warrillow SJ. The case for milrinone. Crit Care Resusc. 2008 Sep;10(3):180-1. PMID: 18798713. [Free fulltext]
- Yamada T, Takeda J, Katori N, Tsuzaki K, Ochiai R. Hemodynamic effects of milrinone during weaning from cardiopulmonary bypass: comparison of patients with a low and high prebypass cardiac index. J Cardiothorac Vasc Anesth. 2000 Aug;14(4):367-73. PMID: 10972598.
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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