Pharmacology for Dentistry

Narcotic Analgesics (Opioids) 79

gated with glucuronic acid and excreted in
urine. Only a small amount of pethidine is
excreted unchanged. Pethidine differs from
morphine in that toxic doses sometimes
cause CNS excitation, characterized by trem-
ors, muscle twitches and seizures; these ef-
fect are largely due to norpethidine.

Adverse effects include nausea, vomit-
ing, respiratory depression, dizziness, dys-
phoria, constipation, urinary retention. Tol-
erance develops to some of these effects and
it has abuse potential.

It is mainly indicated for analgesia, as
preanaesthetic medication, for epidural and
intrathecal analgesia.

FENTANYL

It is a potent opioid analgesic. Chemi-
cally it is N-phenyl-N-propanamide. It in-
teracts predominantly with opioid μ-recep-
tor in human brain, spinal cord and other
tissues. It exerts its principle pharmacologic
effects on the CNS. It is 80-100 times more
potent than morphine, both in analgesia and
respiratory depression.

Adverse effects include respiratory de-
pression (death from hypoventilation), de-
pendence, apnoea, muscle rigidity, bradycar-
dia, arrhythmia, chest pain, GI symptoms,
haemoptysis, abdominal pain, headache,
somnolence, confusion and hallucinations.

It is indicated as a narcotic analgesic
supplement in general or regional anaesthe-
sia, as an anaesthetic agent with oxygen and
skeletal relaxant in selected high risk pa-
tients (e.g. open heart surgery).

METHADONE

It is synthetic compound having same or
more analgesic activity than morphine. It’s

pharmacology and side effects are similar to

that of morphine. It is used in the treatment of

visceral pain and as an antitussive. It is also used

as substitution therapy of opioid dependence.

DEXTROPROPOXYPHENE

It is dextro isomer of propoxyphene

which is an analgesic and possesses antitus-

sive property. It has low analgesic activity

even half of codeine. It is metabolized in liver.

Side effects include vomiting, epigastric dis-

tress and sedation. The demethylated me-

tabolite of propoxyphene is cardiotoxic. It is

used in the treatment of mild type of pain.

TRAMADOL

It is centrally acting synthetic analgesic

compound that is not derived from natural

sources nor is chemically related to opiates.

It acts via opioid receptors in CNS to pro-

duce analgesia and has no abuse potential.

It also inhibits the reuptake of noradrena-

line and serotonin.

It causes less respiratory depression, se-

dation, constipation and urinary retention

than morphine. Its hemodynamic effects are

minimal.

Side effects include nausea, vomiting

and dizziness.

It is indicated in moderate to severe,

acute or chronic pain and in painful diag-

nostic procedures and surgery; arthralgia,

dental pain, musculoskeletal pain, pain as-

sociated with fractures, dislocation and

other related type of pain.

ETHOHEPTAZINE

It is orally active analgesic, similar to

pethidine with low abuse potential. It is gen-

erally used in combination with nonsteroi-