Opioid Analgesics (Narcotics)

Opioid (commonly called narcotic) analgesics are medications that relieve pain by attaching to opioid receptors found in the central nervous system (spinal chord and brain). Opioids are classified as weak or strong. Morphine, a strong opioid, is the "gold standard" against which all other opioid drugs are compared.

They are available in a variety of dosage forms including: oral tablets, capsules and liquids, intravenous injections, intramuscular injections, subcutaneous injections, rectal suppositories and as patches to be applied to the skin. Intravenous injections work more quickly, have a more predictable onset of action and are less painful than subcutaneous (under the skin) or intramuscular injections.

Side effects of opioids (narcotics)

Opioids have a number of side effects and should not be taken in higher doses, more frequently or for longer periods than prescribed. Side effects of opioids (narcotics) include:

• Nausea
• Sedation (drowsiness)
• Respiratory depression (lowers breathing if used for long periods)
• Tolerance (requires larger doses to get the same pain relief)
• Dependence
• Withdrawal symptoms
• Constipation- (codeine causes this the most)-Elderly should use stool softeners and/or bulk forming laxatives when taking codeine
• Orthostatic hypotension (dizziness due to drop in blood pressure when standing up)

Drug Interactions

Each opioid has its own unique set of drug interactions, some of which can be severe and even life threatening. It is important to let your physician and pharmacist know all the medications you are taking (prescription and over-the counter) before adding an opioid medication to your treatment plan.

• Opioids increase the effect of drowsiness when combined with other drugs that cause drowsiness i.e. alcohol, tranquilizers, sleep aids, antidepressant drugs, or antihistamines.
• High doses of an opioid taken by itself or in combination with other drugs have been associated with drug-related deaths.
• Some opioids are less effective when combined with a second opioid.
• Serotonergic syndrome - a potentially life threatening interaction, in which serotonin levels become too high, can occur when some opioids are combined with antidepressants (i.e. duloxitene, tricyclics [amitriptyline, amoxapine, clomipramine, desipramine, doxepin, imipramine, nortriptyline, protriptyline, and trimipramine], SSRI's [citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline], MAOIs [isocarboxazid, phenelzine, selegiline, and tranylcypromine].

Weak opioids (codeine, butorphanol, hydrocodone, pentazocine, propoxyphene, and tramadol) Weak opioids may used to treat mild to moderate pain. They are often combined with acetaminophen or an NSAID (ibuprofen, naproxen, ketoprofen, etc). When a combination product (a product containing both ingredients) is used the dose of the opioid must be limited in order not to exceed the maximum daily dose of the acetaminophen or NSAID.

Codeine - Is a weak opioid, commonly used to treat mild to moderate pain. It is available in low doses over the counter, combined with acetaminophen or NSAIDs such as ibuprofen or ASA.

Codeine must be broken down into morphine to provide pain relief. Approximately 6-10% of the population do not have enough of the enzyme (CYP2D6) that is needed to break it down and therefore do not get adequate pain relief.

A number of medications lower the effectiveness of codeine by interfering with the enzyme needed to break it down including: Amiodarone, Celecoxib, Imatinib, Isoniazid, Ranitidine, Sildenafil, Terbinafine, Yohimbine and many more.

Butorphanol - is a weak synthetic opioid available as a nasal spray and as an injection. It is most commonly used as a nasal spray to manage migraines. It requires a prescription.

Hydrocodone - is a weak opioid that is slightly stronger than codeine. Like codeine it needs to be converted to morphine in the liver to become effective. It is available in tablet and liquid form and requires a prescription.

Pentazocine - is a weak man made (synthetic) opioid available in oral and injectable form. It is used to treat mild to moderate pain. Its pain relieving benefits are subject to a 'ceiling' effect which means that higher dosages do not increase the pain relieving effects and in fact the drug's effectiveness begins to decrease as doses become get too high. This is because the medication has both agonist and antagonist effects at the receptor sites.

Disadvantages of pentazocine include:

• It is more likely to cause hallucinations and other psychotomimetic effects than morphine
• Cardiovascular side effects make it unsuitable in patients with heart disease
• Severe necrosis and sepsis of the skin, subcutaneous tissues, and underlying muscle have occurred (sometime requiring amputation of limb) at the injection sites of addicts who have received multiple doses of pentazocine lactate. Injection sites must be rotated.

Propoxyphene - is a weak opioid analgesic used to treat mild to moderate pain. It is sometimes used in combination with acetaminophen or NSAIDs. Its pain relieving capacity is subject to a 'ceiling' effect, which means that higher dosages not only do not provide more pain relief but can decrease the pain relieving effects. This is because the drug has both agonist and antagonist effects (stimulating and blocking) at the opiate receptor sites. It should not be combined with other morphine-like drugs, since the overall effectiveness of the two drugs will be reduced.

Tramadol - is a weak opioid that also works at the spinal cord. Tramadol 50 mg is similar in effectiveness to Morphine 10 mg. A number of medications may have serious interactions with tramadol, so be sure to tell your doctor and pharmacist about all the medications you are taking (over the counter and on prescription).

Strong opioids - Are used to treat severe pain. They are sometimes combined with acetaminophen or an NSAID (ibuprofen, naproxen, ketoprofen etc.). When a combination product is used the dose of the opioid must be limited to prevent exceeding the maximum daily dose of the acetaminophen or NSAID. Strong opioids include Buprenorphine, Fentanyl, Hydromorphone, Methadone, Morphine and Oxycodone

Meperidine - is available on prescription in oral and injectable form. Pain relief lasts about three hours. It should not be used in patients with renal failure, liver disease or those who have taken MAOI inhibitors within 14 days of receiving the drug.

Side effects including tremors, hyper-reflexia and hallucinations sometimes limit its usefulness.

Morphine - is the "gold standard" against which all other opioids are compared. It is available on prescription in oral and injectable forms. It is a potent stimulator of opiate receptors and blocks pain impulses at several sites including:

• in inflamed peripheral tissues (e.g. knee osteoarthritis)
• the spinal cord
• centrally in the brain

Fentanyl - is a synthetic (man made) slow release opioid that is available in a patch or lozenge form. It can take up to 72 hours to get a high enough level of fentanyl into the bloodstream when treatment is switched to the fentanyl patch. As a result you do not stop your previous painkiller immediately; your doctor will give you instructions for how to gradually decrease your previous painkiller while the Fentanyl builds up in your blood.  The lozenge gives faster pain relief than the patch and is used for 'breakthrough pain. 'Breakthrough pain is pain that comes on suddenly for short periods of time and is not adequately relieved by your normal pain medication. When you stop using Fentanyl patches, it takes up to 72 hours to get the fentanyl out of your system. If you are changing to another painkiller, it will need to be started slowly.