Tilidin

What is Tilidin?

Tilidin is used in the form of hydrochloride or phosphate salt. In Germany, tilidine is available in a fixed combination with naloxone for oral administration (Valoron N and generics); the mixture of naloxone is claimed to lower the abuse liability of the opioid analgesic.[2] This is so that if people take the medication orally (which is the way they are meant to) the opioid blocker, naloxone, has minimal effects on them but if they inject it the naloxone becomes bioavailable and hence antagonises the effects of the tilidine producing withdrawal effects. In Switzerland the original Valoron brand with only tilidine and no naloxone is also available.

As well as its use as an analgesic, tilidine is also commonly used in Germany for treatment of restless legs syndrome.

Tilidine is a controlled substance in most countries, listed in the German BtMG, Austrian SMG, and in the USA under the Controlled Substances Act 1970 as ACSCN 9750 as a Narcotic under Schedule I, with an annual aggregate manufacturing quota of 10 grammes in 2014. It is used as the hydrochloride  and HCl hemihydrate

Adverse effects

Its most common adverse effects are transient nausea and vomiting, dizziness, drowsiness, fatigue, headache and nervousness; less commonly, nausea and vomiting (after repeated dosing), hallucinations, confusion, euphoria, tremor, hyperreflexia, clonus and increased sweating. Uncommonly, somnolence; rarely, diarrhoea and abdominal pain.

It usually comes in its hydrochloride hemihydrate salt form; in this form it is highly soluble in water, ethanol and dichloromethane and appears as a white/almost white crystalline powder.[3] Its storage is restricted by its insensitivity to light and sensitivity to degradation by oxygen, hence necessitating its storage in amber bottles and at temperatures below 30 degrees Celsius, respectively.

Considered a low-to-medium-potency opioid, tilidine has the oral potency of about 0.2, that is, a dose of 100 mg p.o. is equianalgesic to approximately 20 mg morphine sulfate orally. It is administered orally (by mouth), rectally (by a suppository), or by injection (SC, IM or slowly IV) with single doses of 50 to 100 mg, the maximal daily dose being up to 600 mg.opioid, but is rapidly metabolised in the liver and gut to its active metabolite nortilidine and then to bisnortilidine. It is the (1S,2R)-isomer (dextilidine) that is responsible for its analgesic activity.

Synthesis

It is manufactured by a Diels-Alder reaction of 1-N,N-dimethylaminobuta-1,3-diene with ethyl atropate, yielding a mixture of isomers, of which only the (E)-(trans)-isomers are active and are separated subsequently from the mixture by precipitation of the inactive (Z)-(cis)-isomers as zinc complex. The inactive (Z)-(cis)-isomers may be epimerized to the more thermodynamically favored (E)-(trans)-isomers via reflux in diluted phosphoric acid