Warfarin And Antibiotics Interactions

Mechanisms

  • Antibiotics kills intestinal bacteria that make vitamin K
  • Antibiotics inhibit CYP450 enzymes that normally metabolise warfarin

Result

  • Increased INR

References

  1. Baillargeon, J., Holmes, H. M., Lin, Y., Raji, M. A., Sharma, G., & Kuo, Y.-F. (2012). Concurrent Use of Warfarin and Antibiotics and the Risk of Bleeding in Older Adults. The American Journal of Medicine, 125(2), 183–189. http://doi.org/10.1016/j.amjmed.2011.08.014
Advertisements

Potato Gems Of Medical Trivia

A man walks into Bar UC for refuge. The bartender, Sanjay, provides him with a pocket translator his work experience apprentice fetched for him and the man places his order.

Gynaecomastia

  • Benign proliferation of male breast tissue
  • Caused by hormonal imbalance
    • Not enough testosterone compared to oestrogen
    • Medications inducing this include: spironolactone, cimetidine, TCAs, digoxin chemotherapy, metoclopramide and anabolic steroids
    • Conditions inducing this include: liver cirrhosis through SHBG disturbance, hypogonadism, ageing, tumours, renal failure, hyperthyroidism, starvation because testosterone levels drop but oestrogen remains the same
  • Pseudogynaecomastia is fat
  • Imitators: pseudogynaecomastia, breast cancer, mastitis

Cyclophosphamide

  • Affects rapidly dividing cells, like cancer, hair and gut
  • Side effects:
    • Gastrointestinal: nausea, vomiting, loss of appetite, diarrhoea
    • Hair loss
    • Poor wound healing
    • Weird skin and nails

A lady who is almost 80, her wheelchair and her son pass by the bar. She tells bystanders, “Life is quick! You know why? There is too much sin in the world!”

Pulmonary Hypertension

  • High blood pressure in arteries of the lung
  • Causes:
    • Idiopathic
    • Left heart disease
    • Lung disease
    • Pulmonary emboli
    • Secondary to other random conditions
  • Can lead to right heart failure

Sildenafil

  • Trade name: Viagra
  • PDE5 inhibitor
    • Memory aid: PDE5 and Viagra
    • Mechanism: inhibition of PDE5 enzyme –> inhibits second messenger cGMP breakdown —> nitric oxide-mediated vasodilation
  • Indications: pulmonary hypertension, erectile dysfunction

One of the patrons, an overweight redneck, appears to have something stuck in his ears. His wife looks on unsympathetically.

Corticosteroids

  • Many side effects

An irritated farmer waving a pitchfork is on the television in the bar.

Giant Cell Arteritis

  • Average onset age is 72 and minimum is generally 50
  • Symptoms:
    • Headache
    • Joint pain of shoulders and hips, like polymyalgia rheumatica
    • Facial pain, like jaw claudication
    • Scalp pain
    • Visual changes, like blurred vision and blindness
    • Fever
  • Look for temporal artery biopsy and ESR
  • Treat with corticosteroids

Human Herpesvirus Associations

Sometimes, memory aids and mnemonics fall conveniently into place. Other times, the only way to remember something is through its inconvenience, by taking the opposite of whatever it totally should have been.

HHV-6

  • Associated with roseola
  • Memory aid: roseola has 7 letters, which is inconveniently not 6 but certainly less than 8

HHV-8

  • Associated with Kaposi sarcoma
  • Memory aid: Kaposi has 6 letters, so it is not HHV-6, while Kaposi’s has 8 characters in it

Types Of Multiple Sclerosis

Time heals all wounds except relapsing-remitting MS.

And primary-progressive MS.

And secondary-progressive MS.

And whole bunch of other age-related illnesses, like glaucoma, age-related macular degeneration and malignancy.

At least time is good for adhesive capsulitis, alternatively known as frozen shoulder!

Multiple sclerosis

MS is a chronic disease involving immune-mediated attacks on the central nervous system. Demyelination causes mayhem.

As a parallel, Guillan-Barre acutely affects the peripheral nervous system. When it’s chronic, it’s called chronic inflammatory demyelinating polymyopathy.

Symptoms

Neurological symptoms ensue after the disease has passed a threshold.

  • Optic neuritis, characterised by painful visual loss in an eye
  • Numbness, weakness
  • Ataxia, spasticity
  • Fatigue
  • Pain
  • Sexual and urinary dysfunction, such as detrusor overactivity causing urgency

Clinically isolated syndrome is a one-off presentation of demyelination that can progress to MS.

Investigations

MRI can show brain lesions.

CSF analysis can show inflammation.

Evoke potential measurement can show demyelination.

Treatment

Ongoing: immunotherapy agents.

Acute relapse: high-dose corticosteroids.

Spasticity: baclofen

Spasms: benzodiazepines

Mobility: fampridine

Paroxysmal symptoms: carbamazepine

Urinary symptoms: oxybutynin

Pregnancy

The risk of MS relapse is lower during pregnancy and higher in the first 3 months after giving birth.

Summary of major demyelinating illnesses

Central nervous system: clinically isolated syndrome (acute), MS (chronic)

Peripheral nervous system: Guillan-Barre (acute), CIDP (chronic)

References

  1. MS Australia. (2001). Types of MS | MS Australia. [online] Available at: https://www.msaustralia.org.au/about-ms/types-ms [Accessed 20 Jan. 2018].
  2. National Multiple Sclerosis Society. (n.d.). Definition of MS. [online] Available at: https://www.nationalmssociety.org/What-is-MS/Definition-of-MS [Accessed 20 Jan. 2018].
  3. Johns Hopkins Medicine. (n.d.). Guillain-Barre and CIDP. [online] Available at: https://www.hopkinsmedicine.org/neurology_neurosurgery/centers_clinics/peripheral_nerve/conditions/guillain_barre_and_cidp.html [Accessed 20 Jan. 2018].
  4. Multiple sclerosis. In: eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited (eTG November 2017 edition); 2017 Nov.

Why Don’t NSAIDs Cause Malignancy?

Do topical NSAIDs increase the risk of skin cancer? After all, NSAIDs dampen inflammation and immune suppression is a factor that can promote malignancy. The answer is no!

For, on the contrary, research focuses more on the potential of using NSAIDs in the fight against cancer. How can this be?

Think of the mechanism of NSAIDs. They’re non-steroidal anti-inflammatory drugs, meaning they’re medications that reduce inflammation without being from the corticosteroid class.

NSAIDs indirectly inhibit prostaglandin synthesis by directly inhibiting COX enzymes. This provides anti-inflammatory effects and analgesia.

Prostaglandins play a starring role in situations such as fever.

In contrast, other things that are associated with increased malignancy risk have different ways of working.

For example, HIV impacts CD-4 T cells.

Meanwhile, chemotherapy agents have different mechanisms. For example, vincristine disruptively acts on microtubules.

Let’s not forget UV rays, which wreak havoc on the DNA process by inducing mutations.

These are just some of the villains of medicine. Thankfully, there are emerging medications that meet them in combat. But that’s a story for another day!

Hypersensitivity Reactions

Type I: Allergy and anaphylaxis

Type II: Cytotoxic and complement-mediated

Type III: Immune complex

Type IV: Delayed-type hypersensitivity

References

  1. McDaniel, B. (2014, November 24). Type 1, 2, 3 & 4 Hypersensitivity. Retrieved from Stomp on Step 1, http://www.stomponstep1.com/hypersensitivity-type-1-2-3-4-urticaria-anaphylaxis-immune-complexes-i-ii-iii-iv/.
  2. Ghaffar, A. Hypersensitivity reactions. Retrieved from Microbiology and Immunology On-line, http://www.microbiologybook.org/ghaffar/hyper00.htm.