Pain Medications (cont.)
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
In this Article
- Types (classes) of pain medication
- For what conditions are pain medications used?
- What are the differences among the types of pain medications?
- What are the strongest pain medications?
- What are the side effects of pain medications?
- What are the warnings/precautions with pain medications?
- Pain medications list
What are the strongest pain medications?
Opioid analgesics, in general, are the strongest pain-relieving medications. The benchmark drug in this class is morphine -- with other opioids falling above or below it in terms of pain-relieving potential. Near the bottom of the list is codeine, usually prescribed in combination with acetaminophen to relieve, for example, pain resulting from dental work. Codeine is only about 1/10th as powerful as morphine. Opioids more powerful than morphine include hydromorphone (Dilaudid) and oxymorphone (Opana). But the strongest opioid in community use is fentanyl which, in its intravenous form, is 70 to 100 times more potent than morphine. Fentanyl is also available as a long-release patch (Duragesic) and as a lozenge that dissolves in the mouth (Actiq). Sufentanil is even more powerful than fentanyl, but its use, at present is restricted to the intravenous route. However, a transdermal patch containing sufentanil is in clinical trials.
What are the side effects of pain medications?
All NSAIDs come with the risk of gastrointestinal ulceration and bleeding. A newer class of anti-inflammatories, the COX-2 inhibitors, was developed to reduce this risk. It did not, though, eliminate it. In fact, another major issue emerged with these drugs: the possibility of severe and deadly vascular problems with long-term use, including heart attack and stroke.
Most users of acetaminophen experience few, if any, side effects. But the drug can cause liver damage, especially when taking too much or if taken with alcohol.
Opioid analgesics commonly cause drowsiness, dizziness, and respiratory depression. However, these side effects usually disappear with continued use. However, constipation, another common side effect, tends to persist. In addition, opioid use may lead to addiction or dependence. Other possible side effects of opioid analgesics include:
- Euphoria, dysphoria, agitation, seizures, hallucinations
- Lowered blood pressure and heart rate
- Muscular rigidity and contractions
- Nausea and vomiting
- Non-allergic itching
- Pupil constriction
- Sexual dysfunction
- Urinary retention
Mixed opioid agonist-antagonists
Patients can experience symptoms of opioid withdrawal if a straight opioid analgesic, such as morphine, is taken at the same time as an opioid agonist-antagonist drug. Some of these medications include pentazocine (Talwin Nx, Talacen, Talwin Compound), butorphanol, and nalbuphine (Nubain).
The main side effect of muscle relaxants is drowsiness. This may be how they work to "relieve" pain. In addition, carisoprodol (Soma) use may lead to dependence because in the body it is converted into a drug similar to barbiturates; cyclobenzaprine (Flexeril) can cause dry mouth, constipation, confusion, and loss of balance; methocarbamol (Robaxin) discolors the urine to green, brown, or black; both metaxalone (Skelaxin) and chlorzoxazone (Parafon Forte, DSC) should be used with caution in those with liver problems.
Anti-anxiety drugs also carry the risk of sedation, particularly if combined with certain other medications (such as opioid analgesics) or alcohol. Other possible side effects include psychological changes, headache, nausea, visual problems, restlessness, and nightmares. Chest pain and heart pounding are also possible.
Some of the antidepressants used for pain relief are the older tricyclics. These come with numerous side effects classified as anticholinergic, including dry mouth, difficulty urinating, blurred vision, and constipation. Other possible side effects include lower blood pressure, fast heartbeat, palpitations, weight gain, and fatigue.
A few of the newer antidepressants also reduce pain -- and with less risk of anticholinergic issues. Still, the serotonin norepinephrine reuptake inhibitors (SNRIs) may cause the following common side effects:
- Dry mouth
- Ejaculatory difficulties
Side effects associated with the anticonvulsants used for pain management commonly disappear over time. They include dizziness, drowsiness, and swelling of the lower extremities.
In general, short-term and/or low-dose corticosteroid use results in few side effects. But taking corticosteroids long-term can result in severe side effects, including:
- Adrenal insufficiency -- a condition in which the body cannot adequately respond to physical stress
- Bone death
- Cataracts and glaucoma
- Elevated blood pressure
- Elevated blood sugar
- Fluid retention
- Gastrointestinal bleeding
- Mood changes
- Suppression of the immune system
- Trouble sleeping
- Weight gain
- Damage to local tissues
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