H1 and H2 Histamine Blockers (typically found in seasonal allergy medication) shown to significantly blunt training adaptions over 6 week clinical trial

28 people in study, the study participants are taking three times the recommended daily Allegra dose, in addition to a less common H2 inhibitor. All this, only 1 hour prior to a workout.

Post-exercise muscle perfusion is dependent on H1/H2 receptor signaling

To study the effects of H1/H2 blockade on the hemodynamic response during and after interval cycling exercise, healthy adults performed a single exercise session with either placebo (control) or H1/H2 antagonist intake (blockade) on separate days in a randomized and single-blinded design. At rest, acute ingestion of H1/H2 blockers did not alter heart rate, brachial blood pressure, femoral arterial blood flow, or femoral arterial diameter (table S1). The heart rate response during exercise was not different between the placebo and blockade trial (fig. S1A). Muscle perfusion was increased approximately threefold 15 min after exercise and was still ~50% above baseline after 2 hours of passive recovery in the placebo condition. However, the total post-exercise muscle perfusion, expressed as iAUC (incremental area under the curve), was significantly reduced with H1/H2 blockade by ~35%. The brachial arterial blood pressure showed a modest increase during the 2-hour post-exercise period (main effect time) and was, in general, higher after placebo intake (main effect condition). The increase in post-exercise vascular conductance, an important measure of vascular tone, was consequently blunted with H1/H2 blockade. Similar to during exercise, post-exercise heart rate recovery was unaffected by H1/H2 blockade (fig. S1C). Collectively, these data demonstrate that histamine H1/H2 receptors are essential for the regulation of sustained elevation of muscle perfusion following interval exercise.


Interesting. I take Loratadine in the spring / summer for pollen allergy. What alternative is there that does not block H1 receptors?

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Why is this even relevant when the study has people taking 3x the recommended dose? Genuinely curious


and <30 participants

Nasal fluticasone (brand name Flonase). It’s a corticosteroid but not systemically absorbed so it is allowed in competition and training per GlobalDRO: https://www.globaldro.com/US/search/brand-status/eXRkcmdJYmZmckU4YzNidnhLOUZFWkpxalVBMmx6UTE1


You know what blunts training adaptations even more? Hardly sleeping each night because your eyes are bringing and itching so bad you want to take a fork to them, then getting a sinus infection because your nose is so stuffy and runny for a prolonged period of time.
…not that I’m speaking from experience or anything :stuck_out_tongue_winking_eye:


This is covering GERD meds too effectively.

cimetidine (Tagamet)
ranitidine (Zantac)**
nizatidine (Axid)
famotidine (Pepsid)

If I’m reading this right, on these 28 subjects, because they muscles didn’t see increased blood flow post interval session, they would not be able to recover glycogen as quickly. The graphs make it look like a few outliers could wildly swing the results quite a bit.

This was going to be my response too. But on top of the sinuses, add itching due to eczema (which is for me worse at night!). Regardless of the other flaws “Healthy” athletes negative response is hardly relevant as they won’t be taking them!

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