In this case, rectal aspirin is available in the form of a suppository, which is meant to be inserted into the rectum. The procedure is as follows: 

1. Wash hands carefully prior to insertion of the suppository in order to prevent any chances of microbial contamination. 
2. Take the suppository out of its foil wrapping. If necessary, you may consider dipping the tip of the suppository into small quantity of water or lubricating jelly for easy insertion.
3. Lie on either side of the body with the thighs bent upwards toward the chest, or stand on one leg (position as when inserting a rectal thermometer).
4. With one or two fingers gently insert the tips of the round rectal suppository into the anal opening of the patient. In rectum this should be rounded about 1-1 ½ inches (in 2.5-4cm) deep past the anal sphincter for some time thus helping in the effective dissolution and absorption of the paste into the blood.

Similar to oral aspirin, rectal aspirin exerts its action by blocking the cyclooxygenase (COX) enzyme. This enzyme’s main function is to synthesize a number of body chemicals called prostaglandins, which induce processes such as inflammation, pain, and fever. It’s worth noting that aspirin is capable of inhibiting the production of prostaglandins by blocking COX-1 and COX-2, enzymes which assist in the processing of the chemical. This reduces the pain, inflammation and fever associated with the conditions.

Another advantage of rectal administration of aspirin is that the drug can reach the systemic circulation without passing through the stomach and intestines, which is an advantage for patients who have gastric irritation or ulcers while taking oral aspirin. This method of administration is convenient when the patient is unable to take oral medications because of vomiting or any other reasons.

Due to the nature of the medication, that is a rectal suppository, risks while taking it are quite rare assuming that it is used properly. However, it sometimes causes some negative effects particularly in long-term or heavy usage. The most predictable adverse effects surely include the following:

1. Gastrointestinal Irritation: Rectal routes have less frequent adverse parasitic effects than the oral route, but usage of aspirin in the rectal cavity is still capable of irritation leading to discomfort or burning and itchy sensations around the rectum.
2. Bleeding: As it is known, aspirin inhibits the blood’s ability to clot, and therefore use of rectal waxy aspirins increases a patient’s chances of undue bleeding, more so in the event of rectal bleeding or other extreme forms of hemorrhage. This risk is more critical to victims with a past history of gastro- intestinal ulceration or bleeding disorders.
3. Allergic Reactions: Several individuals may be known to present with asthmatic conditions that even l causes aspirin allergy where for instance the patient develops a rash, swelling and difficulty in breathing plunging such effects which may include the use of rectal aspirin.

Like any other medication, rectal aspirin carries risks and should not be taken lightly particularly in certain health conditions and in combination with certain other medications: 

1. Allergic Reactions: Patients that are known to be allergic to aspirin or any other NSAIDs should not use rectal aspirin. 
2. Bleeding Disorders: Patients with diseases such as hemophilia or those who are taking any other agents that affect blood clotting such as warfarin or clopidogrel should also avoid aspirin therapy without the doctor’s recommendation to do so since the drug increases the chance of bleeding.

1. Aspirin & Anticoagulants (e.g., Warfarin):
   Aspirin, including rectal forms, can increase the risk of bleeding when taken with blood thinners like warfarin. This combination may lead to excessive bleeding or bruising, especially in the gastrointestinal tract.
2. Aspirin & NSAIDs (e.g., Ibuprofen):
   Using aspirin rectally with other NSAIDs (like ibuprofen) can significantly increase the risk of gastrointestinal irritation, ulcers, and bleeding. Both aspirin and NSAIDs can irritate the stomach lining, so using them together should generally be avoided.
3. Aspirin & Alcohol:
   Combining aspirin with alcohol can enhance the risk of gastrointestinal bleeding, ulcers, and stomach irritation. This is particularly concerning with rectal forms of aspirin, as the drug is absorbed quickly and can interact with alcohol to increase the risk of stomach issues.
4. Aspirin & Corticosteroids (e.g., Prednisone):
   When taken together, aspirin and corticosteroids increase the likelihood of gastrointestinal bleeding and ulcers. Corticosteroids weaken the stomach lining, and aspirin can further irritate it, leading to a higher risk of bleeding complications.

It’s important to consult a healthcare provider before using rectal aspirin in combination with other medications, particularly anticoagulants, NSAIDs, alcohol, or corticosteroids.

The rectal aspirin dosage is defined differently based on what condition is being treated, the age of the patient and other health characteristics. General dosing guidelines comprise the following parameters:

• For the Relief of Pain and Fever States: The rectal aspirin suppository comes in 300 mg per suppository. The usual dose for adults is one 300 mg suppository every four to six hours, not exceeding 4000 mg within twenty-four hours. However, this may be different due to the health of the individual and should be recommended by a doctor.

If your healthcare professional has instructed you to take a specific quantity of any dosage form of this medication, it is vital that you pay close attention to such instructions to prevent overdose or other adverse effects.

In general practice, rectal aspirin is mostly prescribed since, it is viewed a more innovative way of aspirin therapy. While oral tablet form of aspirin is readily available for the public without a prescription, rectal aspirin footprints are rather smaller and might be used on patients who cannot take the medicine by mouth. 

In case your health provider considers prescribing rectal aspirin, instructions on the effective dose and how long you should use it will be given to you.

1. What is rectal aspirin?

Answer: Rectal aspirin is a formulation of aspirin administered via the rectum, typically used for certain medical conditions where oral administration is not suitable.

2. When is rectal aspirin used?

Answer: It is often used in cases where the patient is unable to take medications orally, such as in severe nausea, vomiting, or postoperative care.

3. How is rectal aspirin administered?

Answer: Rectal aspirin is usually given as a suppository, which is inserted into the rectum where it dissolves and is absorbed into the bloodstream.

4. What are the advantages of rectal aspirin over oral forms?

Answer: Rectal administration allows for quicker absorption, bypasses the gastrointestinal tract, and is beneficial for patients who are vomiting or have difficulty swallowing.

5. What dosage forms of rectal aspirin are available?

Answer: Rectal aspirin is typically available as 300 mg or 600 mg suppositories, though specific formulations may vary by manufacturer.

6. What conditions can rectal aspirin treat?

Answer: Rectal aspirin can be used to treat various conditions, including fever, pain relief, and inflammation, and is sometimes used in the management of arthritis or post-surgical patients.

7. Are there any side effects associated with rectal aspirin?

Answer: Yes, possible side effects of rectal aspirin may include rectal irritation, gastrointestinal bleeding, upset stomach, or allergic reactions.

8. Who should avoid using rectal aspirin?

Answer: Individuals with known allergies to aspirin or salicylates, certain bleeding disorders, or those with gastrointestinal issues should avoid rectal aspirin unless prescribed by a healthcare provider.

9. Can children use rectal aspirin?

Answer: Rectal aspirin should only be used in children under medical advice, especially due to the risk of Reye’s syndrome in those with viral infections.

10. How should rectal aspirin be stored?

Answer: Rectal aspirin should be stored in a cool, dry place away from moisture and heat, and out of reach of children.

11. How is rectal aspirin different from oral aspirin?

Answer: The primary difference lies in the route of administration and absorption. Rectal aspirin bypasses the digestive tract, which may enhance speed of action in certain situations.

12. Can rectal aspirin be used for long-term treatment?

Answer: Long-term use of rectal aspirin should be discussed with a healthcare provider, as the risks of side effects and complications may increase.

13. What should I do if I miss a dose of rectal aspirin?

Answer: If you miss a dose, take it as soon as you remember. However, if it’s nearly time for the next dose, skip the missed dose and return to your regular schedule. Don’t double up on doses.

14. Can I use rectal aspirin with other medications?

Answer: It is important to consult with a healthcare provider before combining rectal aspirin with other medications, particularly blood thinners or other NSAIDs, to avoid potential interactions.

15. How quickly does rectal aspirin work?

Answer: The onset of action for rectal aspirin typically occurs within 30 minutes to 1 hour, but this can vary based on the individual and the formulation used.

16. Is rectal aspirin safe during pregnancy?

Answer: Pregnant women should avoid using rectal aspirin unless specifically directed by a healthcare provider, as it may pose risks, especially in the later stages of pregnancy.

17. What are the signs of an allergic reaction to rectal aspirin?

Answer: Signs of an allergic reaction may include rash, itching, swelling, difficulty breathing, or severe dizziness. Seek medical attention immediately if these occur.

18. Can rectal aspirin cause gastrointestinal issues?

Answer: Yes, while rectal administration may help bypass some gastrointestinal effects, it can still cause irritation and complications, especially if used excessively.

19. Is rectal aspirin effective for migraine relief?

Answer: Some studies suggest that rectal aspirin can be effective in treating migraines, providing relief when oral intake is not possible.

20. What should I do if I experience severe side effects from rectal aspirin?

Answer: If you experience severe side effects, such as significant bleeding, severe abdominal pain, or allergic reactions, seek immediate medical attention.