Analgesics
An analgesic (also known as a painkiller) is any member of
the group of drugs used to relieve pain.
In choosing analgesics, the severity and response to other
medication determines the choice of agent; the WHO pain
ladder, originally developed in cancer-related pain, is widely
applied to find suitable drugs in a stepwise manner.
The analgesic choice is also determined by the type of pain:
for neuropathic pain, traditional analgesics are less effective,
and there is often benefit from classes of drugs that are not
normally
considered
analgesics,
antidepressants and anticonvulsants.
such
as
tricyclic
Major classes:
Paracetamol and NSAIDs:
The exact mechanism of action of paracetamol is uncertain, but
it appears to be acting centrally rather than peripherally (in the
brain rather than in nerve endings).
Aspirin and the other non-steroidal anti-inflammatory drugs
(NSAIDs) inhibit cyclooxygenases, leading to a decrease in
prostaglandin
production.
This
reduces
pain
and
inflammation (in contrast to paracetamol and the opioids).
also
Paracetamol has few side effects and is regarded as safe,
although intake above the recommended dose can lead to
liver damage, which can be severe and life-threatening, and
occasionally kidney damage.
Paracetamol is usually taken orally or rectally, an
intravenous preparation introduced in 2002 has been shown
to improve pain relief and reduce opioid consumption in the
perioperative setting.
NSAIDs predispose to peptic ulcers, renal failure, allergic
reactions, and occasionally hearing loss, and they can
increase the risk of hemorrhage by affecting platelet
function. The use of aspirin in children under 16 suffering
from viral illness has been linked to Reye's syndrome.
COX-2 inhibitors:
These drugs have been derived from NSAIDs. The
cyclooxygenase enzyme inhibited by NSAIDs was discovered
to have at least 2 different versions: COX1 and COX2.
Research suggested that most of the adverse effects of
NSAIDs were mediated by blocking the COX1 enzyme, with
the analgesic effects being mediated by the COX2 enzyme.
The COX2 inhibitors were thus developed to inhibit only the
COX2 enzyme (traditional NSAIDs block both versions in
general).
These drugs (such as rofecoxib, celecoxib and etoricoxib) are
equally effective analgesics when compared with NSAIDs,
but cause less gastrointestinal hemorrhage in particular.
After widespread use of the COX-2 inhibitors, it was
discovered that most of the drugs in this class increased the
risk of cardiovascular events by 40% on average.
This led to the withdrawal of rofecoxib and valdecoxib, and
warnings on others. Etoricoxib seems relatively safe, with
the risk of thrombotic events similar to that of non-coxib
NSAID diclofenac.
Narcotic Analgesics:
There are two types of narcotic analgesics: the opiates and
the opioids (derivatives of opiates).
Opioids are any medication which bind to opioid receptors
in the central nervous system or gastointestinal tract.
There are four broad classes of opioids:
Endogenous opioid peptides (produced in the body:
endorphins)
Opium alkaloids (morphine, codeine)
Semi-synthetic opioids (heroin, oxycodone, hydrocodone,
dihydrocodeine, hydromorphone)
Fully synthetic opioids (pethidine , fentanyl, tramadol)
Opioids are used in medicine as strong analgesics, for relief
of severe or chronic pain.
There is no upper limit for the dosage of opioids used to
achieve pain relief, but the dose must be increased gradually
to allow for the development of tolerance to adverse effects
(for example, respiratory depression).
Some people with intense pain get such high doses that the
same dose would be fatal if taken by someone who was not
suffering from pain."
There have been debates over the addictive potential of
opioids vs. the benefit of their analgesic properties for
treating non-malignant chronic pain, such as chronic
arthritis.
Some experts believe opioids can be taken safely for years
with minimal risk of addiction or toxic side effects.
The enhanced quality of life which opioids may provide the
patient must be considered.
Common side effects and adverse reactions:
nausea
vomiting
drowsiness
dry mouth
miosis (contraction of the pupil)
orthostatic hypotension (blood pressure lowers upon
sudden standing)
urinary retention
constipation and/or fecal impaction
Most severe side effects and adverse reactions:
respiratory depression
fatal overdose
Specific agents:
In patients with chronic or neuropathic pain, various other
substances
may
have
analgesic
properties.
Tricyclic
antidepressants, have been shown to improve pain in what
appears to be a central manner.
Anticonvulsants are used to treat neuropathic pain with
differing degrees of success. Anticonvulsants are most
commonly used for neuropathic pain as their mechanism of
action tends to inhibit pain sensation.
Sedatives
A sedative or tranquilizer is a substance that induces
sedation by reducing irritability or excitement.
Hypnotic (also called soporific) drugs are a class of
psychoactives whose primary function is to induce sleep
and to be used in the treatment of insomnia, and in
surgical anesthesia.
At higher doses of sedatives may result in slurred
speech, staggering gait, poor judgment, and slow,
uncertain reflexes.
Doses of sedatives such as benzodiazepines, when used
as a hypnotic to induce sleep, tend to be higher than
amounts used to relieve anxiety, whereas only low doses
are needed to provide a peaceful and calming sedative
effect.
Types of sedatives:
Barbiturates
pentobarbital
phenobarbital
Benzodiazepines
diazepam
midazolam
alprazolam
Herbal sedatives
cannabis
Nonbenzodiazepine sedatives
zaleplon
zopiclone (Imovane, Zimovane)
Antihistamines
diphenhydramine
Other
chloral hydrate
alcohol
opiates and opioids
Therapeutic use:
Doctors often administer sedatives to patients in order to
relieve the patient's anxiety related to painful or anxietyprovoking procedures. Although sedatives do not relieve
pain in themselves, they can be a useful combination to
analgesics in preparing patients for surgery.
It is commonly given to patients before they are
anaesthetized, or before other highly uncomfortable and
invasive procedures like fiber optic bronchoscopy, cardiac
catheterization, colonoscopy or MRI.
They also increase tractability and compliance of children or
demanding patients.
Patients in intensive care units are almost always sedated
(unless they are unconscious from their condition anyway).
Dangers of combining sedatives and alcohol:
Sedatives
and
alcohol
are
sometimes
combined
recreationally or carelessly. Since alcohol is a strong
depressant that slows brain function and depresses
respiration, the two substances compound each other's
actions and this combination can prove fatal.
Sedatives and amnesia:
Sedatives can sometimes leave the patient with long-term or
short-term
amnesia.
Lorazepam
is
one
such
pharmacological agent that can cause anterograde amnesia.
Intensive care unit patients who receive higher doses over
longer periods, typically via IV drip, are more likely to
experience such side effects.
Muscle Relaxant
A muscle relaxant is a drug which affects skeletal muscle
function and decreases the muscle tone. It may be used to
alleviate symptoms such as muscle spasms, pain, and
hyperreflexia. The term "muscle relaxant" is used to refer to
two major therapeutic groups: neuromuscular blockers and
spasmolytics.
Neuromuscular
blockers
act
by
interfering
with
transmission at the neuromuscular end plate and have no
central nervous system (CNS) activity.
They are often used during surgical procedures and in
intensive care and emergency medicine to cause paralysis.
Spasmolytics, also known as "centrally acting" muscle
relaxants, are used to alleviate musculoskeletal pain and
spasms and to reduce spasticity in a variety of neurological
conditions.
While both neuromuscular blockers and spasmolytics are
often grouped together as muscle relaxants
Uses of muscle relaxants:
- Use in intensive surgeries and emergency procedures to
induce paralysis
- Antispasmodic
- Treats symptoms of fibromyalgia i.e. stiffness, fatigue, and
body aches
- Alleviate back pain and neck pain
- Used as a treatment for tension headaches
Commonly used muscle relaxants list:
Carisoprodol: muscle relaxant that works by blocking the
pain sensations from the nerves by acting on the central
nervous system. It is used to temporarily relieve pain from
muscle pain, spasms, sprains, and strains. It is also used as
an antidepressant.
Diazepam: aside from relieving muscle pains and spasms, it
also alleviates acute alcohol withdrawal, convulsion, and
anxiety related symptoms. It acts on the brain and nerves
and produced a temporary calming effect on the user.
Cyclobenzaprine: used to treat muscle spasm and pain
associated with acute musculoskeletal conditions.
Metaloxone:
relatively
strong
muscle
relaxants
that
produced little side effects, it is used to relax muscle and
lessen muscle pain and spasms. Increased viability is
impressed when taken with food.
Methacarbamol: a central muscle relaxant used to treat
skeletal spasm and helps to relax muscles and reduce
muscle pains associated from sprains, strains, and muscle
stress.
The most common side effects of muscle relaxants are:
Vision changes, such as double vision or blurred vision Dizziness,
drowsiness
Dry mouth
Less common side effects, such as stomach cramps or pain,
nausea and vomiting, constipation, diarrhea, hiccups, confusion,
nervousness, restlessness, irritability, flushed or red face,
headache, heartburn, weakness, and sleep problems also may
occur and do not need medical attention unless they do not go
away or they interfere with normal activities.
More serious side effects are not common, but may occur.
Anyone who experiences breathing problems, facial swelling,
fainting, unusually fast or unusually slow heartbeat, fever,
tightness in the chest, rash, itching, burning, red, or bloodshot
eyes, or unusual thoughts or dreams after taking muscle
relaxants should seek medical help.
Muscle relaxants may interact with some other medicines. When
this happens, the effects of one or both of the drugs may change
or the risk of side effects may be greater. Anyone who plans to
take muscle relaxants should let the physician know all other
medicines,
including
over-the-counter
medicines, that he or she is taking.
or
nonprescription
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