MD2140 – PharmaNUS

Category: MD2140 (page 1 of 6)

From Sensitivity to Tolerance: Understanding Aspirin Desensitisation

I was confused when I met a patient with documented aspirin sensitivity who was still taking low-dose aspirin every day. If aspirin can trigger bronchospasm, why would they continue using it? And how does this desensitisation process actually work?

This question opens the door to a critical intersection of pharmacology, immunology, and respiratory medicine. Aspirin sensitivity is common enough to matter clinically, yet nuanced enough that its mechanisms can be confusing when first studying the pharmacology of non-steroidal anti-inflammatory drugs (NSAIDs). Here is a concise guide to help you understand what’s going on and why desensitisation can be a life-changing intervention for some patients. Continue reading

Domperidone vs. Metoclopramide: A Pharmacological Face-Off

April 11, 2025 / phcdgs / 0 Comments

What is the difference between domperidone and metoclopramide? Why is domperidone not always preferred, as it has less risk of CNS adverse effects?

Gastrointestinal motility disorders and nausea are common clinical challenges, and two dopamine antagonists — domperidone and metoclopramide — are often used in their management. Although both act on dopamine D2 receptors, key differences in their pharmacokinetics, central nervous system penetration, and adverse effect profiles make the choice between them more than a matter of availability. Let’s unpack the differences.

Can allopurinol be taken during acute gouty attacks?

October 9, 2024 / phcdgs / 0 Comments

Is it safe to continue allopurinol therapy during an acute gout attack, or does it risk worsening the flare?

Acute gout attacks are characterized by painful joint inflammation caused by immune cells attacking urate crystals. While chronic management to lower blood urate levels is crucial for preventing flare-ups, the approach to using urate-lowering therapies such as allopurinol during an acute gout attack continues to evolve. This blog will clarify some of the clinical considerations and evidence surrounding the use of allopurinol during acute gout episodes.

The Dilemma: Traditional Teaching vs. Emerging Evidence. Traditionally, initiating or adjusting allopurinol during an acute attack was discouraged, as altering uric acid levels can exacerbate symptoms. This concept led to a common recommendation of holding off allopurinol until the acute phase subsides. However, recent evidence has challenged this approach, suggesting that allopurinol, if already in use, should be continued during acute attacks to maintain steady uric acid levels and prevent rebound hyperuricaemia.

Why does fingolimod have cardiac effects?

October 6, 2024 / phcdgs / 0 Comments

Fingolimod is prescribed as an immunosuppressant for managing multiple sclerosis, but why should clinicians be particularly cautious about its cardiovascular effects during initial dosing?

Fingolimod, an oral immunomodulatory drug approved for the treatment of multiple sclerosis (MS), has a unique mechanism of action that makes it highly effective in reducing MS relapses. However, like many medications, it comes with a specific set of adverse effects that need careful consideration, particularly its impact on the cardiovascular system. Here’s what you need to know.

How Does Fingolimod Work?
Fingolimod functions as a sphingosine-1-phosphate (S1P) receptor modulator. It sequesters lymphocytes in the lymph nodes, reducing their migration out, and preventing them from crossing into the central nervous system (CNS) where they would normally contribute to the inflammatory damage seen in MS. This modulation of S1P receptors is crucial to its therapeutic effect, but it also leads to unintended cardiovascular effects.

The Difference Between Mycophenolate Mofetil (MMF) and Mycophenolate Sodium (MPS)

October 2, 2024 / phcdgs / 0 Comments

What is the difference between mycophenolate mofetil (MMF) and mycophenolate sodium (MPS)

Understanding the nuances between different formulations of a drug is crucial to ensuring optimal patient care. Mycophenolate mofetil (MMF) and mycophenolate sodium (MPS) are two formulations of the immunosuppressant mycophenolic acid, commonly used to prevent organ rejection in transplant recipients and to manage autoimmune conditions. Despite their similar purposes, there are important differences between them that influence their clinical use.

The Discovery of Fingolimod: From Nature to the Clinic

October 1, 2024 / phcdgs / 0 Comments

Fingolimod is prescribed as an immunosuppressant for managing multiple sclerosis, but is it true that it originates from a parasitic fungus like Cordyceps?

Fingolimod was originally derived from myriocin, a compound isolated from a curious source: Isaria sinclairii, a type of parasitic fungus that is related to the well-known Cordyceps species. This fungus, which is prominent in traditional Chinese medicine for its rejuvenating properties, offered a glimpse into something incredible—its bioactive compounds showed a profound impact on immune modulation. Researchers began to understand that these molecules could interact with immune cells, leading to potential therapeutic effects.

Improved Patient Education on Adverse Effects of Allopurinol: A Focus on SCAR

September 29, 2024 / phcdgs / 0 Comments

The Health Science Authority (HSA) and Agency for Care Effectivness (ACE) in Singapore have recently published a new patient fact sheet on safe usage of allopurinol.

Medical education constantly evolves to meet the needs of patients, and a new allopurinol patient factsheet provides a great example of how better communication can make a significant difference in patient safety and outcomes. This new patient factsheet for allopurinol usage in treating gout will enhance patient safety and the effective management of this painful condition. As a cornerstone in the management of gout, allopurinol has been in use for decades. The new patient factsheet provides clear and accessible information for patients. In particular, it provides important information regarding adverse effects, particularly the rare but serious condition known as Severe Cutaneous Adverse Reaction (SCAR), for patients taking allopurinol.

Hydroxychloroquine – New Safety Advisory on Congenital Malformations, Phospholipidosis, and Myasthenia Gravis Aggravation

September 21, 2024 / phcdgs / 0 Comments

The Health Science Authority (HSA), Singapore, has announced that Sanofi-Aventis Pte Ltd has issued a “Dear Healthcare Professional Letter” to provide critical updates on the safety profile of Plaquenil® (Hydroxychloroquine sulphate). Healthcare professionals are urged to take note of these new findings, particularly in patients who are pregnant, those with myasthenia gravis, or individuals at risk of developing phospholipidosis.

Key Safety Update – Increased Risk of Major Congenital Malformations: A 2021 study by Huybrechts et al. has reported a small but significant increase in the relative risk of major congenital malformations linked to hydroxychloroquine when administered during the first trimester of pregnancy. The risk becomes more pronounced at higher daily dosages (≥ 400 mg/day).

Pseudoephedrine and the Risk of PRES and RCVS: A New Focus on Patient Safety

May 6, 2024 / phcdgs / 0 Comments

It is important to learn about the rare, serious adverse effects of over-the-counter (OTC) medications. Pseudoephedrine, a commonly used decongestant, is one such drug that can have unexpected neurological consequences.

Recent updates in adverse event reports have highlighted the rare but important risks of posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS) associated with pseudoephedrine. Understanding these risks is crucial.

Pseudoephedrine: A Common but Potent OTC Drug

Pseudoephedrine is a sympathomimetic agent that acts by vasoconstricting the blood vessels in the nasal passages, which helps relieve nasal congestion. It is often included in many combination medications for treating the common cold, allergies, and sinus congestion. Pseudoephedrine-containing products have been marketed in Singapore since the 1980s, and no significant safety issues were reported locally until recently. However, overseas cases of rare neurological syndromes linked to pseudoephedrine have been documented, prompting regulatory agencies to enhance warnings and recommendations.

Which fruit to avoid with fexofenadine?

September 27, 2023 / phcdgs / 0 Comments

It is advised to avoid taking fexofenadine with fruit juices. But does this apply to all fruit juices or only grapefruit juice? And what about tomato juice – are tomatoes not also fruit? And why the warning only about the juice – what happens if you eat the fruit instead of drinking the juice?

Grapefruit and Drug Metabolism – A Closer Look at CYP Interactions: Many of us might have come across warnings about the potential interaction between grapefruit juice and certain medications. Let’s delve deeper into the science behind this. Grapefruits, along with other specific citrus fruits like pomelos and Seville oranges (often termed as bitter oranges or sour oranges), are rich in polyphenols, notably furanocoumarins. These compounds play a crucial role in inhibiting various cytochrome P450 enzymes, including CYP3A4, CYP1A2, CYP2C9, and CYP2D6.

Why does this matter? The inhibition of the CYP3A4 enzyme, in particular, impedes its ability to effectively metabolize certain drugs. As a result, there can be an unintended increase in the drug levels within the bloodstream, amplifying the risk of side effects or even toxicities. It’s noteworthy that CYP3A4 is pivotal for the metabolism of a wide range of medications. Consequently, grapefruit’s interaction can potentially affect the efficacy and safety of medications such as statins (targeting high cholesterol), calcium channel blockers (for managing hypertension), calcineurin inhibitors (used in immunosuppression), and benzodiazepines (prescribed for anxiety and insomnia).

Fruit and Fexofenadine – Reduced Absorption: Contrary to the increased plasma concentration of drugs seen following inhibition of CYP enzymes, fruit juices decrease intestinal absorption of the second-generation H1 antihistamine, fexofenadine. The mechanism behind this interaction involves intestinal transporters, specifically organic anion-transporting polypeptides (OATPs).