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, such as tricyclic

antidepressants and anticonvulsants.

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 also inflammation (in contrast to paracetamol and the

opioids).

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 anxiety-provoking 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 or

nonprescription medicines, that he or she is taking.

Thank You