Drug Management of Pains

This is a contributing post from PHARM. KOKARI  T.S.

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. (International Association For The Study Of Pains, 2015).

Introduction:

Pain is a symptom of an underlying condition

It can affect a person’s general function and productivity

Because of its severity sometimes, pain has been used as an argument to permit people who are terminally ill to end their lives (Physician assisted suicide or euthanasia)

Pain that lasts a long time (> 6 months) is called chronic pain e.g cancer, peripheral neuropathy

Pain that resolves quickly ( <30 days) is called acute pain.

ASSESSMENT OF PAIN

Evaluation should include a detailed description of the pain ( sharp, burning, dull, aching etc)

Patient full history, psychosocial assessment, medication history paying attention to factors that influence the pain

Diagnostic laboratory test, imaging, including computer tomography (CT) and magnetic resonance imaging (MRI)

NB: pain is a subjective phenomenon and quantitative assessment is difficult (Breivik et al., 2008)

NEUROTRANSMITTERS AND PAIN

Various neurotransmitters in the dorsal horn of the spinal cord are involved in pain modulation

These include glutamate, GABA,NA, serotonin and peptide molecules e.g endogenous opiods – enkephalins, endorphins.

MAJOR TYPES OF PAIN

Nociceptive pain

Neuropathic pain

Psycogenic pain

Nociceptive pain

Caused by actual or potential damage to tissues e.g cut, burns, an injury

The pain is felt due to tiny nerve endings become activated or damaged (nociception)

Pain can be managed with traditional pain killers such as NSADS, opiod analgesics

Neuropathic pain.

 is caused by a problem with one or more nerves themselves

 the function of the nerves is affected in a way that it sends pain messages to the brain

 Pain is often described as burning, stabbing, aching or  like an electrical shock

 Causes includes trigeminal neuralgia, diabetic neuropathy, multiple sclerosis, cancer, alcoholism.

Psychogenic pain

 It can be induced by social rejection, broken heart, grief, or other emotional events

Headache, back pain, or stomach pain are some of the most common types of psychogenic pain

 treatment may include psychotherapy, antidepressants , analgesics.

RESULTS OF UNTREATED PAIN

Depression, anxiety, decreased socialization

Sleep disturbance

Impaired ambulation

PAIN MGT GOALS

Relieve acute and chronic pain

Minimized side effects

Improve patient quality of life

DRUGS USED IN THE MGT OF PAIN

WHO  Analgesic Ladder

 Mild to moderate pain

     Step 1: Non – opioids e.g Paracetamol or NSAIDS

 Moderate to severe pain

     Step2: Mild opioids e.g Codeine, with or without NSAIDS

 Severe pain

      Step 3: Strong opioids e.g Morphin

NON- STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)

Are effective for treating nociceptive pains

They have analgesic, antipyretic and anti-inflammatory actions

Are good for treating pains associated with rheumatoid arthtritis, gouty arthritis, headache, waist and back pains, toothache etc

Are not effective for treatment of visceral pain e.g angina pectoris

They don’t relieve neuropathic pain much

Examples; Aspirin, diclofenac, aceclofenac, ibuprofen,

Celecoxib etc

  

MOA

Inhibition of cyclooxynase enzymes (cox 1 and cox 2) thereby inhibit the synthesis of prostaglandin          ( inflammatory mediator) and to some extent synthesis of the thromboxanes( platelet aggregation)

Adverse effects of NSAIDS

i. On GIT

Causes peptic ulcer or GIT bleeding

PGE 2 and PGI 2 inhibit gastric acid secretion, increase blood flow through the gastric mucosa and have cytoprotective action

ii. Nephrotoxicity

Cause chronic kidney failure

PGE2 and PGI 2 are powerful vasodilators synthesized in the renal medulla and glomeruli respectively and are involved in the control of renal blood flow and excretion of salt and water.

iii. Other adverse effects include;

Skin rashes ( Steven’s Jonson syndrome)

Prolonged bleeding (anti-platelet action)

NB: aspirin raises plasma urate levels at low doses by inhibiting uric acid secretion in the renal tubules. Thus should not be used in patients with gouty arthritis

DRUGS USED IN THE MGT OF NEUROPATHIC PAIN( Nep)

1st line analgesics

Tricyclic antideppresants (TCAs)

The TCAs provide the best evidence of efficacy in the mgt of Nep

MOA: these drugs block the re-uptake of NA and serotonin in the nerves and also have Na channel blocking

Example: Amitriptyline

Adverse effects: dry mouth, constipation, drowsiness

ii. Anticonvulsants

Example: Pregabalin or gabapentin

Gabapentin produce significant pain relief and significant improvement in measures of quality of life and mood

MOA: inhibit the release of excitatory neurotransmitters e.g glutamate and activate the GABA receptors (inhibitory NT)

Adverse effects: dizziness, headache, blurred vission, drowsiness

2nd  Line analgesics

Example: Topical Lidocaine (5%)

Is used for patients with localized peripheral NeP such as postherpetic neuralgia

MOA: is a Na channel blocker

3rd Line analgesics

Example: Tramadol

4th Line analgesics

Opioid analgesics e.g Morphin

 Antispastticity agents (muscle relants)

Example: Baclofen

Clinical uses- is an agent of choice for treating spinal spasticity and spasticity associated with multiple sclerosis 

Adverse effects: depression, nausea, confusion

 High strength vit B complex

Example: Neurovit forte

Used in treatment of peripheral neuropathy