Opioids, sublingual

Opioids maybe administered in a variety of routes including oral (tablet and liquid), sublingual, rectal, transdermal, transmucosal, intravenous, subcutaneous, and intraspinal. While the oral and transdermal routes are most common, the method of administration is based on patient needs (severity of pain) and characteristics (swallowing difficulty and preference). Oral opioids have an onset of effect of 45 minutes, so intravenous or subcutaneous administration maybe preferred if more rapid relief is desired. Intramuscular injections are not recommended because of pain at the injection site and wide fluctuations in drug absorption and peak plasma concentrations achieved. More invasive routes of administration such as PCA and intraspinal (epidural and intrathecal) are primarily used postoperatively, but may also be used in refractory chronic pain situations. PCA delivers a self-administered dose via an infusion pump with a preprogrammed dose, minimum dosing interval, and maximum hourly dose. Morphine, fentanyl, and hydromorphone are commonly administered via PCA pumps by the intravenous route, but less frequently by the subcutaneous or epidural route. 

Suboxone is a combination of buprenorphine (opioid partial agonist) and naloxone. It is presented as sublingual tablets and is used as an adjunct in the treatment of opioid dependence and in premedication or perioperative analgesia. A side-effect of opioids is drowsiness. 

Opioid dependence Sublingual Initially, 12-16 mg/day, beginning at least 4 hr after last use of heroin or short-acting opioid. Maintenance 16 mg/day. Range 4-24 mg/day. Patients should be switched to buprenorphine and naloxone combination, which is preferred for maintenance treatment. 

Weinberg, D.S., et al. 1988. Sublingual absorption of selected opioid analgesics. Clin Pharmacol Ther 44 335. 

Phenazocine is a high-efficacy agonist used particularly in biliary colic for it has less capacity than other opioids to cause spasm of the sphincter of Oddi. It may be administered sublingually if the patient is vomiting. 

Sublingual buprenorphine is an alternative to methadone in treating opiate dependence, but its opioid agonist effects pose the risk of intravenous abuse and subsequent dependence. This abuse potential may be hmited by using a combination of buprenorphine with naloxone, which will precipitate opiate withdrawal when given... 

The effects of buprenorphine (sublingually or by injection) in an opioid-dependent population have been studied (23,24). There was benefit in using buprenorphine to counteract opioid withdrawal effects in patients with chronic heroin use and subsequent dependence. However, the results are limited and the benefits shortterm if psychosocial support is not in place as part of an overall treatment package before buprenorphine is prescribed (25). 

A sublingual formulation that combines buprenorphine and naloxone is thought to be ideal for reducing parental buprenorphine abuse. In a small pilot study in nine opioid-dependent individuals already stabilized on buprenorphine 8 mg/day, naloxone 0, 4, or 8 mg was added (27). The addition of naloxone did not precipitate opiate withdrawal. 

Administration (FDA) for the treatment of opioid addiction. Treatment is initiated with buprenorphine alone administered sublingually, followed by maintenance therapy with a combination of buprenorphine and naloxone (Suboxone) to minimize abuse potential. The partial agonist properties of buprenorphine limit its usefulness for the treatment of addicts who require high maintenance doses of opioids. However, conversion to maintenance treatment with higher doses of methadone, a full agonist, is possible. 

BILIARY TRACT After the subcutaneous injection of 10 mg morphine sulfate, the sphincter of Oddi constricts, and the pressure in the common bile duct may rise more than tenfold within 15 minutes this effect may persist for 2 hours or more. Fluid pressure also may increase in the gallbladder, producing symptoms that vary from epigastric distress to typical biliary cohc. All opioids can cause biliary spasm. Atropine only partially prevents morphine-induced biliary spasm, but opioid antagonists prevent or relieve it. Nitroglycerin (0.6-1.2 mg) administered sublingually also decreases the elevated intrabiliary pressure. 

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