Learn the Differences and Side Effects among Different Types of Pain Medications


Pain medications can be divided into two classes: Prescription and nonprescription drugs. The nonprescription, also known as over-the-counter drugs treat short-term and acute pain such as headaches or minor muscle sprains. These generally include mild anti-inflammatory drugs and acetaminophen. Prescription pain relievers often treat moderate-to-severe pain and chronic pain such as surgery, trauma, labor, fibromyalgia, and cancers. Opioids analgesics such as morphine are the strongest pain-relieving option. A major difference between the two types of drugs, anti-inflammatories and opioid analgesics, is that increasing anti-inflammatory drugs doesn’t increase the pain relief provided by the drug. If you have developed a high tolerance to opioids, then you can increase the dose for more pain relief. Even though there is no limit to opioid dosage, high levels can cause lethal side effects.

The side effects for NSAIDS include:

  • Gastrointestinal bleeding and ulcers
  • Vascular problems such as heart attack and stroke with prolonged usage

The few side effects, if any for acetaminophen include:

  • Liver damage mainly when taken at high doses and with alcohol

The many side effects of opioids include:

  • Drowsiness
  • Dizziness
  • Respiratory depression
  • Constipation
  • Addiction
  • Dependence
  • Lowered blood pressure and heart rate
  • Muscular rigidity and spasms
  • Non-allergic itching
  • Pupil constriction
  • Hallucinations
  • Nausea and vomiting
  • Sexual dysfunction
  • Urinary retention
  • Euphoria, dysphoria, agitations
  • Seizures

The side effects of mixed opioid agonist-antagonists:

  • Withdrawal symptoms can occur when straight opioid analgesics are taken together with an opioid agonist-antagonist drug (pentazocine, butorphanol, and nalbuphine).

The side effects of muscle relaxants include:

  • Drowsiness
  • Carisoprodol can cause dependence
  • Cyclobenzaprine possibly causes dry mouth, constipation, loss of balance, and confusion
  • Methocarbamol can cause urine discoloration to green, brown, or black.  
  • Metaxalone and Chlorzoxazone together can be lethal in people with liver problems.

The side effects of anti-anxiety agents include:

  • Sedation often occurs when combined with opioid analgesics and alcohol
  • Psychological changes
  • Nausea
  • Headaches
  • Restlessness
  • Visual problems
  • Nightmares
  • Chest pain
  • Heart pounding
  • Nervousness

The side effects of antidepressants include:

The older tricyclic antidepressants:

  • Anticholinergic-dry mouth, blurred vision, difficulty urinating, and constipation
  • Lower blood pressure
  • Fast heartbeat
  • Palpitations
  • Weight gain
  • Fatigue

The newer antidepressants with serotonin norepinephrine reuptake inhibitors (SNRIs):

  • Anorexia
  • Constipation
  • Asthenia
  • Dry mouth
  • Dizziness
  • Ejaculatory difficulties
  • Headaches
  • Insomnia
  • Nausea
  • Sweating

The side effects of anti-seizure drugs usually disappear over time:

  • Dizziness
  • Drowsiness
  • Swelling in lower extremities

The side effects for corticosteroids are less when taken at a low dose or short-term. If drugs taken over a prolonged period of time, severe side effects include:

  • Adrenal insufficiency
  • Atherosclerosis
  • Bone death
  • Cataracts and glaucoma
  • High blood sugar
  • High blood pressure
  • Mood changes
  • Gastrointestinal bleeding
  • Osteoporosis
  • Sleep issues
  • Weak immune system
  • Damage to local tissues
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