Pharmacology

Scombroid Poisoning

When there is too much histamine in fish, people should beware.

The Scombroid family of fish includes tuna and mackerel. When stored improperly, there can be too much histamine, which is not degraded by cooking. This causes symptoms of histamine excess, such as urticaria and all the usual culprits of unwellness.

The clinical diagnosis is based on history of multiple people being affected, rather than a single person with an allergy, as well as the redness of the presentation. Theoretically, the fish’s histamine can be measured. Histamine metabolites should show in the urine.

An antihistamine medication is the answer to this issue, such as the H1 antagonist diphenhydramine.

References

  1. Sicari V, Patel P, Zabbo CP. Diphenhydramine. [Updated 2025 Mar 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526010/.
  2. Liddiard, S., Nickson, C. and Nickson, S.L. (2024). Scombroid Poisoning. [online] Life in the Fast Lane • LITFL. Available at: https://litfl.com/scombroid-poisoning/.

Professor Or Serial Killer? The Sequel

Various tasteful games are played in life. Some of them range from Drummer Or Serial Killer? to Professor Or Serial Killer?

I’d like to introduce a new variation: Medication Or Elf From The Lord Of The Rings?

Levemir: Medication Or Elf?

This is…

(obligatory drum roll)

…a medication. It’s a form of long-acting insulin.

Ritonavir: Medication Or Elf?

This is…

(next obligatory drum roll)

…also a medication. It’s an anti-HIV agent whose mechanism is HIV-1 protease inhibition.

References

  1. NPS Medicinewise. 2020. Levemir FlexPen. [online] Available at: <https://www.nps.org.au/medicine-finder/levemir-flex-pen-injection> [Accessed 2 February 2021].
  2. NPS Medicinewise. 1997. Ritonavir. [online] Available at: <https://www.nps.org.au/australian-prescriber/articles/ritonavir> [Accessed 2 February 2021].

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

Dornase Alfa

Dornase alfa is a mucolytic medication used in the treatment of cystic fibrosis. By cutting apart extracellular DNA, it makes mucus thinner.

References

  1. Genentech. (2018). How Pulmozyme works. [online] Available at: http://www.pulmozyme.com/how-pulmozyme-CF-treatment-works [Accessed 20 Jan. 2018].
  2. Yang, C., Chilvers, M., Montgomery, M., & Nolan, S. J. (2016). Dornase alfa for cystic fibrosis. The Cochrane Database of Systematic Reviews, 4, CD001127.

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!