Drug Groups

approved; investigational

Description

A narcotic analgesic proposed for moderate to severe pain. It may be habituating. [PubChem]

Indication

Indicated in the treatment of moderate to severe pain. Consider for those prone to constipation or respiratory depression. Tramadol is used to treat postoperative, dental, cancer, and acute musculosketetal pain and as an adjuvant to NSAID therapy in patients with osteoarthritis.

Pharmacology

Tramadol, a centrally-acting analgesic, exists as a racemic mixture of the trans isomer, with important differences in binding, activity, and metabolism associated with the two enantiomers. Although Tramadol is a synthetic analog of codeine, it has a significantly lower affinity for opioid receptors than codeine.

Toxicity

LD₅₀=350mg/kg (orally in mice)

Affected Organisms

Biotransformation

The major metabolic pathways appear to be N- and O- demethylation and glucuronidation or sulfation in the liver. One metabolite (O-desmethyltramadol, denoted M1) is pharmacologically active in animal models.

Absorption

Racemic tramadol is rapidly and almost completely absorbed after oral administration. The mean absolute bioavailability of a 100 mg oral dose is approximately 75%.The mean peak plasma concentration of racemic tramadol and M1 occurs at two and three hours, respectively, after administration in healthy adults.

Half Life

23 +/- 10 minutes

Protein Binding

20%

Elimination

Tramadol is eliminated primarily through metabolism by the liver and the metabolites are eliminated primarily by the kidneys. Tramadol and its metabolites are excreted primarily in the urine with observed plasma half-lives of 6.3 and 7.4 hours for tramadol and M1, respectively. Approximately 30% of the dose is excreted in the urine as unchanged drug, whereas 60% of the dose is excreted as metabolites.

Distribution

* 2.6 L/kg [male 100 mg intravenous dose]
* 2.9 L/kg [female 100 mg intravenous dose]

Clearance

* 5.9 mL/min/Kg [Healthy Adults, 100 mg qid, MD p.o]
* 8.5 mL/min/Kg [Healthy Adults, 100 mg SD p.o]
* 6.89 mL/min/Kg [Geriatric, (<75 yr), 50 mg SD p.o.]
* 4.23 mL/min/Kg [Hepatic Impaired, 50 mg SD p.o.]
* 4.23 mL/min/Kg [Renal Impaired, Clcr10-3mL/min, 100 mg SD i.v.]
* 3.73 mL/min/Kg [Renal Impaired, CLcr<5 mL/min, 100 mg SD i.v.]
* 6.4 mL/min/Kg [Male following a 100 mg IV dose]
* 5.7 mL/min/Kg [Female following a 100 mg IV dose]

References

External Links