Chronic pain is common condition. Unfortunately, chronic pain is a problem that is difficult to diagnose and treat. Diagnosis is subjective, relying primarily on the patient’s report of symptoms. Pain cannot be confirmed with an electronic device, laboratory work or imaging tests. The physician has to perform a thorough workup of the patient to assess the pain. Drug therapy is primarily based on acetaminophen, anti-inflammatories, opioids, and adjunctive therapy such as anti-depressants.

In 1999, the FDA approved a new formulation of lidocaine called Lidoderm patch, which contains 5% lidocaine. The 12-hour patch slowly delivers lidocaine, which hinders the transmission of pain signals by blocking sodium channels. The patch is indicated for chronic pain associated with post-herpetic neuralgia. Since its approval, the patch has also been effective and used for post-operative pain associated with unilateral knee replacement, burn-injury pains, refractory pain related to sickle cell crisis, and chronic low back pain.

How would you approach this pain managment case?

TM is a 58 year-old man who presents with community-acquired pneumonia, diabetes type II, hypertension, and low back pain. At home, he takes metformin 500 mg three times daily, lisinopril 10 mg daily, and Lidoderm patch daily. Upon admission, he is started on ceftriaxone 1 gram IV every 24 hours, doxycycline 100 mg orally twice a day, and albuterol and ipratropium via nebulization every 4 hours as needed for shortness of breath. Metformin is held. For better control of blood sugars, the physician starts Levemir (insulin detemir) 10 units SQ every 12 hours and Novolog (insulin aspart) 1 unit for every 10 grams of consumed carbohydrates per meal. For pain, he prescribes morphine 1 mg IV every 2 hours as needed for pain level of 6-9 and Lidoderm patch daily as needed for pain.

On admission, labs are sodium 138, potassium 5.1, chloride 116, CO2 19, BUN 31, creatinine 1.4, and random glucose of 230. His hemoglobin A1C (HgAIC) is 8.1%. His chest x-ray is positive with bilateral infiltrates.

On Day 2 and 3, you notice that the patient is requesting morphine every 2 hours and is taking up to 14 mg per day. His complaint is always the same: shooting pain radiating up and down his back. His pain is so unbearable that he cannot walk (although he walks at home). On the medication administration record (MAR), you notice that the patient has not received a dose of Lidoderm patch. The physician wants to discharge the patient on Tylenol #3 (acetaminophen 300 mg/codeine 30 mg). He calls you to ask for the conversion of morphine to Tylenol #3. What is your response?

1. Review his current medication list

On his MAR, you notice that the patient has received 14 mg of morphine per day but not one dose of his Lidoderm patch. Why? The orders for Lidoderm and morphine are as needed. The nurse can either give morphine or Lidoderm patch. In this case, the nurse opts for the opioid which is correct. Morphine works within minutes, which is appropriate for as needed use. However, the Lidoderm patch has a delayed onset of action (with plasma lidocaine levels detectable in 3 hours). Therefore, using Lidoderm patch on as needed basis is inappropriate.

2. Review his pain level, location of pain, and timing of his pain

Nursing has documented that the patient complains of pain in his lower back and legs. He complains every 3 to 4 hours after he wakes up and until he sleeps. His pain level is between 6 and 8. He reports pain relief after the morphine.

3. Recommend a Pain Management Regimen

It is best not to treat a patient with opioids if the pain is previously well-managed with a non-narcotic. You decide to call the physician and recommend giving Lidoderm patch daily (not PRN). The use of morphine should decline as the patch begins to work. The prescription of Tylenol #3 may not be needed.

4. Research and prepare to answer

Regardless of your recommendation, the physician may still insist on giving Tylenol #3. If that is the case, honor the request and perform your research. To convert from opioid to another opioid, it is recommended to 1) add up the total daily dose of the opioid, 2) calculate 50% of the opioid, and 3) locate the conversion factor for oral codeine (which is 200 mg of oral codeine for every 10 mg of IV morphine). In this patient, 50% of morphine 14 mg is 7 mg. Based on the conversion factor, the patient will need at least 140 mg of oral codeine. Each Tylenol #3 tablet contains 30 mg of codeine. For ease of administration, the patient can receive Tylenol #3 one tablet every 6 hours as needed for pain (total codeine dose = 120 mg).

Outcome of the case

The physician agrees with the recommendation to give Lidoderm patch on a regular schedule. On the next day, the patient receives the patch. The patient asks for morphine twice. By early evening, the patient is discharged without opioids.

References

Buck ML. Use of Lidocaine for Analgesia in Children and Adolescents. Pediatr Pharm. 2013:19(12).

Hines R, Keaney D, Moskowitz MH, et al. Use of Lidocaine patch 5% for chronic low back pain: a report of four cases. Pain Med. 2002 Dec; 3(4):361-5.

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