Lofexidine

Absorption

Lofexidine has a good oral bioavailability and the peak plasma concentration occurs after 2-5 hours of oral administration. The bioavailability is registered to be even higher than 72%. About 30% of the administered dose of lofexidine is lost during first-pass metabolism. The absorption is registered to be very rapidly recirculated in the gut. After oral administration of 0.8 mg of lofexidine, a maximal dose of 1.26 ng/ml is achieved after 3 hours.

Toxicity

Lofexidine did not exhibit genotoxic, mutagenic nor mutagenic potential. Administration at gestational period showed a reduction in the neonatal weight, survival, and increased abortion.

The Uses of Lofexidine

An tihypertensive.

Background

Lofexidine is a non-opioid centrally acting alpha2-adrenergic receptor agonist that was first approved for the treatment of opioid withdrawal in the United Kingdom in 1992. It was first studied for use as an antihypertensive in 1980, but its researched was stopped as it was found less effective for the treatment of hypertension than clonidine. Lofexidine was then repurposed for the treatment of opioid withdrawal, as it was seen to be more economical and have fewer side effects than clonidine. Lofexidine was developed by US Woldmeds LLC and it was approved by the FDA on May 16, 2018.

Indications

Lofexidine is indicated for mitigation of symptoms associated with acute withdrawal from opioids and for facilitation of the completion of opioid discontinuation treatment. It is the first non-opioid medication for the symptomatic management of opioid discontinuation.
Opioid withdrawal syndrome is a debilitating manifestation of opioid dependence. This condition is extremely unpleasant lasting several days with some of the main features being abdominal pain, nausea, diarrhea, mydriasis, lacrimation, and piloerection. These symptoms are often observed after abrupt reductions in the opioid dose and can be resolved by re-administration of the opioid.

Definition

ChEBI: Lofexidine is a member of imidazoles, a dichlorobenzene, an aromatic ether and a carboxamidine. It has a role as an alpha-adrenergic agonist and an antihypertensive agent.

brand name

Lofexidine (Rhone-Poulenc Rorer).

Pharmacokinetics

In clinical trials, lofexidine presented more severe opioid withdrawal effects than observed with methadone. On the other hand, in clinical trials of methadone withdrawal, lofexidine effectively reduced withdrawal symptoms, especially hypotension. The clinical reports have also indicated that lofexidine presents a better outcome when used briefly. In phase 3 clinical trials, lofexidine was shown to generate a significantly higher completion rate of opioid discontinuation. Some pharmacological studies were performed and there were no off-target effects reported.

Metabolism

Lofexidine metabolic ratio is highly variable among people. It is metabolized mainly by the activity of CYP2D6 and in a minor degree by CYP1A2 and CYP2C19. These enzymes catalyze the hydroxylation of lofexidine and the opening of imidazoline ring to form N-(2-aminoethyl)-2-(2,6-dichlorophenoxy)propanamide. This metabolite is deamidated and forms 2-(2,6-dichlorophenoxy) propionic acid and 2,6-dichlorophenol. These three main metabolites are inactive.