Monday 25 October 2010

Digoxin Toxicity - Predisposing Factors


Digoxin Toxicity Predisposing Factors (System Related):
  • General - Old age
  • Cardiac - Myocardial ischaemia
  • Respiratory - Acute hypoxia
  • Hepatobiliary - Reduced hepatic clearance
  • Metabolic - Electrolyte disturbance, Hypokalaemia, Hypercalcaemia
  • Endocrine - Hypothyroidism
  • Renal - Reduced renal clearance, Renal insufficiency
  • Pharmacology - Drug interactions
Drug Interactions:
  • Amiodarone
  • Anticholinergic drugs
  • Captopril
  • Clarithromycin
  • Diltiazem
  • Erythromycin
  • Ibuprofen
  • Nifedipine
  • Quinidine
  • Verapamil
Image: Digoxin Molecule Wikipedia Public Domain

Wednesday 6 October 2010

Hexamethonium Man (Paton, 1954)


“He is a pink complexioned person, except when he has stood for a long time, when he may get pale and faint. His handshake is warm and dry. . . . He is thin because his appetite is modest; he never feels hunger pains and his stomach never rumbles. . . . As old age comes on he will suffer from retention of urine and impotence but frequency, precipitancy, and strangury will not worry him.”

Background:
  • This description by Paton, in 1954, summarises the effects of pharmacologic blockade of ganglionic transmission.
  • Hexamethonium blocks ganglionic nicotinic acetylcholine receptors.
  • Hexamethonium thus causes dysfunction of the efferent sympathetic & parasympathetic pathways.
Consequences of this disruption include:
  • Erectile dysfunction
  • Impaired bladder emptying
  • Orthostatic hypotension
  • Saliva production decreased
  • Sweating absence (anhidrosis)
  • Tear production decreased

Reference:
Paton WD. Transmission and block in autonomic ganglia. Pharmacol Rev 1954;6:59-67

Image: from http://ridzuanzaidi.blogspot.com/
Tags: Anhidrosis - Autonomic Nervous System - Erectile Dysfunction - Hexamethonium - Hypotension - Man - Orthostatic Hypotension - Parasympathetic Nervous System - Sympathetic Nervous System - Sweating
Posted by Medicalchemy
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Medicalchemy Toxicology Blog

This Medicalchemy (TM) blog will be about Toxicology related topics.

Tags: Blog - Toxicology
Posted by Medicalchemy
Medicalchemy Group: Images - Mnemonics - Anatomy - Cardiology - Dermatology - Drugs - Endocrinology - Gastroenterology - Genetics - Geriatrics - Gynecology-Haematology-Immunology- Infection - Metabolic Medicine - Nephrology - Neuroscience - Nutrition - Obstetrics - Oncology - Ophthalmology - Orthopaedics - Otolaryngology - Pathology-Pharmacology - Physiology- Psychiatry -Public Health - Respiratory - Surgery - Toxicology - Vascular.