Off Label Medications Used to treat pain

When a medication is used off-label it means that the drug was approved for treating a condition other than what it is being used for in the current situation. For instance some medications that have been found useful for pain treatment include antidepressants, anticonvulsants and antiarrhythmics.

Antidepressants for pain

A number of antidepressants are used to treat chronic pain, even when depression is not a factor. One way they possibly work is by increasing chemicals in the body that reduce the level of pain signals transmitted along nerve pathways. An advantage of antidepressants is that they do not cause dependence and the dose required to relieve pain is often lower than that needed for depression. A disadvantage is that they do not relieve pain immediately and may require several weeks to become effective. Antidepressants are sometimes used to treat:

• Nerve pain - from diabetes, shingles, strokes etc.
• Fibromyalgia
• Migraines (as a preventative)

Antidepressants that are used to treat chronic pain include:

• Tricyclic Antidepressants
  • Amitriptyline
  • Imipramine
  • Nortriptyline
  • Desipramine
• SSRIs (Selective Serotonin Reuptake Inhibitors)
• Paroxetine
• Fluoxetine
• Sertraline
• SNRIs (Selective Norepinephrine Reuptake Inhibitors)
  • Venlafaxine
  • Duloxetine

Side effects of antidepressants

Tricyclic antidepressants have more side effects than SSRIs and SNRIs. SNRIs appear to be more effective than SSRIs for neuropathic pain relief.

Side effects of antidepressants include:

• Dry mouth (common with tricyclic antidepressants)
• Drowsiness (take before bedtime-tricyclic antidepressants)
• Wakefulness and/or drowsiness (paroxetine, fluoxetine, venlafaxine, duloxetine)
• Constipation (eat fiber, drink lots of water)
• Weight gain (common with tricyclics and varies with SSRIs and SNRIs)
• Difficulty with urination (common with tricyclics)
• Orthostatic hypotension (drop in blood pressure upon standing- can result in dizziness)
• Sexual dysfunction
• Rapid heart rate
• Anticonvulsants for chronic pain

Anticonvulsant medications are one of the fastest growing drugs on the market due to their increasing use in treating neuropathic pain (pain from shingles, diabetic neuropathy, and damaged nerves post-injury or surgery) and migraine prevention.

Anticonvulsants are a group of drugs commonly used for treating epilepsy. They work by slowing down overactive nerves. Nerves damaged by injury or disease can become overactive leading to chronic pain. By slowing down overactive nerves, anticonvulsants provide effective pain relief in two thirds of patients suffering from chronic nerve pain; however they do not appear to be effective for acute pain.

Anticonvulsants used to treat pain include:

• Carbamazepine
• Clonazepam
• Gabapentin
• Lamotrigine
• Phenytoin
• Pregabalin
• Tiagapine
• Topiramate
• Valproic acid
• Zonisamide

Side effects of anticonvulsants

Side effects of anticonvulsants may include:

• Dizziness, drowsiness
• Weight change (weight loss-topiramate and zonisamide) (weight gain-gabapentin)
• Headache
• Dry mouth
• Diarrhea

Side effects that should be reported to your physician immediately include:

• Confusion, mental slowing, loss of contact with reality
• Speech disorder
• Depression, thinking about killing yourself or planning or trying to do so
• Chest pain, Peripheral edema (fluid retention)
• Rash, yellowing of the skin or eyes
• Vision problems, poor vision, visual hallucinations, glaucoma
• Abnormal gait (manner of walking), Ataxia (irregular muscle coordination)

Drug Interactions with anticonvulsants

There are a large number of drug interactions associated with the use of anticonvulsants. You should give your physician and pharmacist a list of all medications that you are taking (over the counter and on prescription) before starting an anticonvulsant. The following are a few of the many drug interactions associated with anticonvulsants including:

• Birth control pills may become less effective (alternate forms of birth control are recommended for added protection
• Blood thinners (some anticonvulsants lower blood levels of blood thinners)
• MAOI antidepressants (life-threatening serotonin syndrome)

Antiarrhythmics for pain

Some antiarrhythmics work by slowing the electrical conduction in the heart. These include lidocaine, tocainide and mexiletine. Neuropathic pain is often associated with rapid electrical impulses at damaged nerve endings and along nerve pathways. Since these medications slow electrical conduction along nerve pathways they have also been shown to be effective for relieving neuropathic pain.

Side effects experienced with antiarrhythmics are primarily gastrointestinal and can be relieved with over the counter antacids.

Drug interactions - There are a number of drug interactions associated with antiarrhythmics. It is important for you to give your doctor and pharmacist a list of all the medications you are taking (over the counter and on prescription) before starting an antiarrhythmic. The following are a few of the many drug interactions associated with antiarrhythmics, including:

• Increased blood thinning with warfarin
• Caffeine (builds up in the blood)
• Cigarette smoking (increases the breakdown of some antiarrhythmics decreasing their effectiveness)
• Fluvoxamine (increases blood levels of some antiarrhythmics)
• Opioids (delay the effectiveness of some antiarrhythmics)