Tramadol: An Appropriate Analgesic?

Uses/Indications: Tramadol is a synthetic codeine analogue and a weak μ opioid receptor agonist. Tramadol also inhibits neuronal reuptake of norepinephrine and serotonin and may facilitate serotonin release. Therefore, it is recommended for acute and chronic pain and may be used alone to treat mild pain or adjunctively in a multimodal plan to treat moderate to severe pain.

Studies: 1. A prospective, randomized blinded study performed in 2003, with 30 female dogs separately evaluated IV morphine and tramadol for postoperative analgesia after ovariohysterectomy. The animals were monitored for 6 hours after analgesic administration and researchers reported no significant differences between the 2 groups with regard to analgesia, sedation, SpO2, pH and blood gases, cardiovascular variables, catecholamine, glucose, and cortisol levels.

Adverse Effects:  Canines: CNS Effects – sedation, agitation, anxiety, dizziness

Gastrointestinal – inappetence, vomiting, constipation, or diarrhea

Felines:  Dysphoria, mydriasis, and dose avoidance (unpalatability)

Dosing:  Canines: 1 – 5 mg/kg PO up to four times daily**

Felines:  4 mg/kg PO twice daily

Case studies show tramadol can also be useful in a transdermal formulation for felines

**Compounded oil based suspensions can be dose customized and are stable for 180 days**

**In humans, the principle active metabolite (O-methyl tramadol, M1) is more active at μ receptors than the parent drug. Felines produce significant amounts of M1, but dogs only produce minimal amounts. Oral bioavailability is 93% in cats but only 65% in canines and dogs clear tramadol more rapidly, therefore the dosing interval must be adjusted.

Contraindication/Warnings: 1. Combination product (Ultracet^®-Acetaminophen/Tramadol) is contraindicated in cats.

2. Tramadol is commercially available in a 50mg tablet and 10mg/ml suspension. (This limitation usually makes compounding necessary.)
3. Use with caution in drugs that can cause CNS or respiratory depression.
4. Use with caution in animals with pre-existing seizure disorders or receiving other drugs that may lower the seizure threshold. 

Monitoring Parameters:

1. Clinical efficacy
2. Adverse effects