Magnesium

Daylesford, Victoria – a place with abundant mineral springs, some high in Magnesium

I’m on an electrolyte role! Today, Magnesium – important both physiologically and pharmacologically.

The therapeutic benefits of Magnesium have been known for at least 400 years, when Epsom Salts (MgSO4) were first discovered to have a laxative effect!

Miller’s Anaesthesia Ch59 is an excellent resource on electrolytes.

BT_PO1.72 Describe the function, distribution and physiological importance of sodium, potassium, magnesium, calcium and phosphate ions

BT_PO 1.57 Describe the pharmacology of antiarrhythmic agents and their clinical applications including magnesium (and lots more)

SS_OB1.12 Describe the pharmacology of agents used for the treatment of pre-eclampsia including magnesium, hydralazine and labetolol

Magnesium is largely an extracellular ion T/F

Magnesium acts as a physiological calcium antagonist T/F

Magnesium is a co-factor for the production of ATP during oxidative phosphorylation T/F

Hypermagnesaemia predisposes patients to Torsades de Pointes T/F

A Mg2+ ion blocks the open NMDA receptor channel at normal RMP preventing ion flux T/F

Magnesium causes smooth muscle relaxation throughout the body T/F

Magnesium has class I and class IV anti-arrhythmic effects T/F

BT_PO 1.60 : Digoxin

Describe the pharmacology of drugs used to manage acute or chronic cardiac failure, including: sympathomimetics, phosphodiesterase inhibitors, digoxin, diuretics, ACE inhibitors, nitrates and beta blockers

 

A guest post from an ex PEX chair :

Agatha Christie knew a lot about poisoning, probably as a result of working with a pathologist.  (https://bookshop.theguardian.com/catalog/product/view/id/323440/).  After reading this book, you would have to be brave to go into an English garden.
   
One of her garden poisons was foxglove, which made me think of digoxin.   As did the recent death of Miles Vaughan Williams, who classified anti arrhythmics.   So often we see digoxin toxicity in clinical practice.     An old drug, but one that continues to be used, and is loved by examiners because it allows for candidates to demonstrate  an understanding of many different facets of pharmacology.    

TRUE/FALSE  Digoxin is highly protein bound, hence the introduction of another highly protein bound drug is likely to precipitate toxicity

TRUE/FALSE  Digoxin is primarily excreted renally, and frequently patients who are prescribed digoxin may have borderline or impaired renal function which may precipitate toxicity

TRUE/FALSE  Overdosage of digoxin may be treated using Digibind (R)  which is an example of an immunoglobulin which binds to digoxin to cease its therapeutic effect

TRUE/FALSE  Hypokalaemia is frequently seen in digoxin toxicity, reflecting digoxin’s inhibition of the Na/Ca pump

TRUE/FALSE  The bioavailability of digoxin is reasonably high (approx 70%) allowing for oral loading doses to be only slightly slower in reaching therapeutic effects compared with intravenous loading doses