The correct answer is Aspirin.

- Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) can precipitate bronchospasm in patients with asthma, especially those with the condition known as Aspirin-Exacerbated Respiratory Disease (AERD).
- This occurs because aspirin inhibits the cyclooxygenase (COX) enzyme, leading to a shunting of arachidonic acid metabolism towards the production of leukotrienes, which are potent bronchoconstrictors.
- This leukotriene-mediated pathway can cause acute bronchospasm and worsening of asthma symptoms.

In contrast:

- Paracetamol (acetaminophen) is generally considered safe for asthmatic patients, although rare hypersensitivity reactions can occur.

- Diclofenac, like aspirin, is an NSAID and may potentially cause bronchospasm, but it is less commonly implicated compared to aspirin.

- Tramadol is an opioid analgesic with minimal effect on bronchospasm and is not contraindicated in asthma.

Therefore, aspirin should be avoided in asthmatic patients due to the risk of exacerbating bronchospasm.

Reference: Harrison's Principles of Internal Medicine, 20th Edition, Chapter 323: Asthma, Page 2100