Podcast Summary: Dr. Chapa’s Clinical Pearls

Episode Title: ASA Desensitization in Pregnancy
Release Date: February 28, 2025
Host: Dr. Chapa
Main Focus: Evidence-based review and discussion of low-dose aspirin (ASA) desensitization in pregnancy for those with NSAID hypersensitivity, especially in the context of preeclampsia prevention.

Overview of the Episode

Dr. Chapa dives into a fresh, not-yet-officially-published study on oral aspirin desensitization in pregnant patients with self-reported NSAID allergy, particularly those at high risk for hypertensive disorders like preeclampsia. He discusses the clinical challenge, relevant protocols, data from the Singaporean study, and practical pearls for implementation or referral.

Key Discussion Points and Insights

Introduction & Context

• History of Aspirin: Opens with a humorous reflection on a vintage aspirin commercial, establishing aspirin's longstanding presence in medicine and its current importance in obstetrics.

• Aspirin Use in Pregnancy: Reminds listeners that aspirin is the only globally endorsed medication for preeclampsia prevention but notes controversy on optimal dose and timing.

  • “Aspirin is hot in the literature regarding what dose we should use in pregnancy for preeclampsia prevention or hypertensive disorders in pregnancy in general and when it should be stopped.” (00:38)

• Clinical Dilemma: Raises the question—what to do when a pregnant patient with preeclampsia risk factors also has an NSAID allergy?

Aspirin Dosing Controversy

• International Guidelines Differ: FIGO recommends 100–150 mg daily; ACOG is more variable, but 81 mg ("baby aspirin") is actually the minority recommendation. Many protocols suggest 100–150 mg or even 162 mg (two ‘baby aspirins’).
  • “I can tell you that 81 milligrams and below is the minority of the recommendation. The majority say 100 to 150 or 162.” (07:30)
• When to Stop Aspirin:
  • Varied recommendations; new data suggest 36 weeks gestation (rather than "until delivery") is again becoming standard to balance benefit and bleeding risk.

The Singapore Study: ASA Desensitization Protocol

• Patient Selection:

  • 34 pregnant women, all with self-reported NSAID hypersensitivity (angioedema, urticaria, asthma, etc.), enrolled over nearly three years.
  • Most had longstanding NSAID reactions (median 11 years) and nearly all (97%) had issues with at least two NSAIDs.
  • “These were not skin tested, they weren’t challenged. It's like they report a history...real stuff, not like, oh, I take it, I get a little itchy, which is important to know. But we're talking about real issues here, like angioedema, right?” (13:17)

• Exclusions:

  • No history of NSAID-induced anaphylaxis, respiratory disease, or severe cutaneous reactions allowed in this protocol.

• Desensitization Protocol (Singapore)

  • Dosing:
    • 8 sequential oral doses: 1, 2, 4, 8, 16, 32, 37, and 50 mg of aspirin, administered every 20 minutes.
    • Final cumulative dose: 100 or 150 mg, based on provider preference (not 81 mg).
  • Premedication:
    • None given beforehand; patients monitored, with antihistamines or epinephrine available for reactions if needed.
  • Observation:
    • Vitals monitored each dose; observed for an hour post final dose (to cover the four-hour window typical for most hypersensitivity reactions).
  • Protocol Duration:
    • Total protocol takes about 2–2.5 hours plus one hour of observation.
    • “Using little aliquots, increasing increments of milligrams of aspirin to introduce to the patient...over a setting of like two to two and a half hours, right? Eight different incremental doses until they hit 100 or 150 milligrams.” (07:30)

Study Outcomes & Results (17:13)

• Demographics:

  • Median age: 34 years; median gestational age at desensitization: 13.5 weeks.
  • ~30% with co-existing asthma.
  • Most common reaction: angioedema (swelling, particularly periorbital, lips, cheeks).

• Reactions During Desensitization:

  • 16 of 34 developed mild periorbital angioedema; 2 had urticaria.
  • Median onset: 4 hours after starting protocol.
  • 7 had symptoms after 100 mg cumulative dose; 9 after 150 mg.

• Severity:

  • All reactions mild (no anaphylaxis, no bronchial or severe GI symptoms, no hospitalizations).
  • “All mucocutaneous reactions were mild. And, and we did not observe episodes of anaphylaxis, bronchial or gastrointestinal symptoms, and other serious adverse events. None of the participants required IM epinephrine or hospital admission.” (21:38)

• Continuation and Success:

  • 94% (32/34) successfully completed and continued daily aspirin, including 14 of 16 who had hypersensitivity reactions—those managed with oral antihistamines over ~7 days.
  • Split: 17 stayed on 150 mg, 15 on 100 mg. Some dose reduction needed for persistent angioedema.
  • “The short of it is using this protocol...resulted in no severe adverse reaction. Some minor temporary issues...but nobody went to the hospital and nobody died. That's pretty darn reassuring.” (22:54)

• Adherence:

  • Self-reported: 100% (though not directly observed).

Clinical Pearls & Recommendations

• Efficacy and Safety:
  • Desensitization up to 150 mg aspirin is feasible and safe in most, even in the early second trimester.
  • Mild reactions can be managed outpatient.
  • Severe reactions (anaphylaxis, SJS, etc.) were NOT included—avoid in those cases.
• Who Should Do This?
  • Can be performed in an outpatient clinic with proper monitoring capacity—or refer to allergy/immunology.
  • “If treating the patient in your location is something like, I'm not digging that, then send it to the allergist.” (22:09)
• When to Stop?
  • Protocol stopped at 36 weeks or onset of labor, matching the current trend in recommendations.
• Implications:
  • Should not unnecessarily withhold aspirin from pregnant women at risk for preeclampsia due to mild/moderate NSAID hypersensitivity; desensitization is a clinic-friendly option.

Evidence Table Highlight

• Global Disagreement:
  • Table S1 from the discussed study showcases the worldwide variation in aspirin dosing and stopping recommendations (75–162 mg, stop at 34–36 weeks or delivery), emphasizing the lack of consensus but general support for higher dosing than common US practice.

Notable Quotes & Memorable Moments

• On the need for desensitization:
  • “In somebody who is allergic to that class of medication, can we give them aspirin? That's the first question. Or number two, can we do low dose aspirin desensitization during that pregnancy? That's what we're talking about.” (04:19)
• On study size vs. impact:
  • “Not huge numbers here, but you don't need huge numbers for this because it works.” (04:58)
• On protocol simplicity:
  • “These authors out of Singapore give a really, really nice, easy to adopt algorithm that can be done in an outpatient clinic setting. Takes about two and a half hours.” (04:44)
• On mild reactions:
  • “You get angioedema… it’s different than anaphylaxis. I mean, I don’t want to minimize angioedema. Angioedema is horrible. Fine, it looks terrible, could cause some morbidity for the patient, but it’s not anaphylaxis.” (21:51)
• On practical implementation:
  • “If treating the patient in your location is something like, I'm not digging that, then send it to the allergist.” (22:09)
• On the take-home message:
  • “Using this protocol of oral aspirin desensitization…resulted in no severe adverse reaction. Some minor temporary issues…that’s pretty darn reassuring.” (22:54)
• On clinical significance:
  • “These preliminary results support the role of desensitization in avoiding the unnecessary withholding of aspirin in pregnant women with NSAID hypersensitivity and so have significant implications for antenatal care, particularly in settings with a high prevalence of preeclampsia.” (approx. 23:40)

Timestamps for Important Segments

• 00:38 — Opening discussion on the historic importance of aspirin and the controversy around dosing & timing
• 07:30 — International guidelines & dosing variation: the predominance of 100–150 mg recommendations
• 13:13 — Study methods: patient characteristics, eligibility, and desensitization protocol specifics
• 17:13 — Singapore study table & survey of worldwide guidelines
• 21:38 — Side effects observed (angioedema versus anaphylaxis, clinical management)
• 22:54 — Outcomes, adherence, clinical pearls

Summary & Actionable Points

• Pregnant patients at risk for preeclampsia and with self-reported NSAID allergy (excluding severe/life-threatening reactions) can be considered for clinic-based aspirin desensitization using incremental oral doses up to 100–150 mg, with careful monitoring.
• Desensitization is generally safe, and mild mucocutaneous reactions are common and manageable; severe reactions are rare (not observed in this small study).
• International opinion varies widely regarding optimal dosing and duration of aspirin therapy in pregnancy, but higher doses (100–150 mg) and cessation by 36 weeks are trending.
• Clinicians not comfortable with the protocol should refer to allergy/immunology for multidisciplinary management.

Closing Thought:
Dr. Chapa concludes with enthusiasm for innovation in antenatal care and encourages providers not to withhold aspirin unnecessarily—armed now with a safe, practical desensitization protocol for most NSAID-allergic patients. This small but promising series provides a new tool for preeclampsia prevention in this subset of patients.