A seventy years old lady with rheumatoid arthritis and recent history of surgery was a passenger in a car. Her car was hit behind. She developed a typical for this situation injury. She was advices by her daughter in law to use the following:

Question

A seventy years old lady with rheumatoid arthritis and recent history of surgery was a passenger in a car.  Her car was hit behind. She developed a typical for this situation injury. She was advices by her daughter in law to use the following:

BlackTom AI · Accepted Answer

Whiplash from a rear-end collision produces neck soft-tissue injury and pain that is often managed by analgesic measures and sometimes by adjuvant supplements that modulate endorphin/enkephalin systems.

1) Relevant knowledge points and concepts
- Rear-end impact commonly causes whiplash-associated disorder (neck strain, muscle spasm, chronic pain).  
- dl-Phenylalanine (DLPA) is a racemic mixture: D-phenylalanine inhibits enkephalinase (the enzyme degrading endorphins/enkephalins), prolonging endogenous opioid activity and producing analgesic effects; L-phenylalanine is a precursor to tyrosine and catecholamines and can support mood.  
- The other listed amino acids have different primary roles: cystine/cysteine for keratin/glutathione; lysine for protein/collagen synthesis and viral suppression; methionine as a methyl donor/S-adenosylmethionine precursor; tyrosine as catecholamine precursor but not an enkephalinase inhibitor.

2) Step-by-step reasoning
- Identify the typical injury: rear impact → whiplash → pain that may benefit from agents that raise endogenous opioids.  
- Match supplements to mechanism: among options, only DLPA has a documented mechanism (D-phenylalanine inhibiting enkephalin-degrading enzymes) that can provide analgesia for musculoskeletal pain. L-phenylalanine's catecholamine precursor role further helps mood, useful after trauma.

3) Intermediate/mechanistic steps
- D-phenylalanine → inhibits enkephalinase → decreased breakdown of enkephalins/endorphins → increased endogenous opioid signaling → reduced pain perception.  
- No numerical calculation is required.

4) Why the correct answer is correct
- DLPA directly supports increased endogenous opioid activity and has been used as an adjunct for chronic and musculoskeletal pain, making it the most appropriate among the choices for whiplash-type pain.

5) Why other options are incorrect
- Cystine/cysteine: supports structural protein and antioxidant synthesis, not analgesia.  
- Lysine: important for collagen and immune function, not a pain relief agent.  
- Methionine: methyl donor role, not specific analgesic.  
- Tyrosine: catecholamine precursor (may affect alertness/mood) but lacks the enkephalinase inhibition and analgesic profile of DLPA.

6) Conclusion/confirmation
Therefore, the correct choice is e. dl-phenylalanine, which matches the provided answer.

A seventy years old lady with rheumatoid arthritis and recent history of surgery was a passenger in a car. Her car was hit behind. She developed a typical for this situation injury. She was advices by her daughter in law to use the following:Single choice

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