Pharmacology for Dentistry

80 Section 2/ Drugs Acting on CNS

dal antiinflammatory drugs for mild to mod-
erate type of pain.

OPIOID AGONISTS/ANTAGONISTS

They are classified as in table 2.3.2.

PENTAZOCINE

It is agonist-antagonist of morphine and
is used as an analgesic. It exerts morphine like
action. It is a partial agonist at opioid receptors
and is effective in mild to moderate type of
pain associated with surgery, trauma, burns,
colics, toothache, cancer, in labour and as
preanaesthetic medication. It is kappa receptor
agonist with weak mu antagonist or partial
antagonist properties. It causes tachycardia
and rise in BP due to sympathetic stimulation.
Tolerance and dependence develops on
repeated use. It is effective orally. It is oxidized
and glucuronide conjugation occurs in liver
and excreted in urine.

NALORPHINE

It is an N-allylnormorphine, semisyn-
thetic congener of morphine. The agonistic

actions are produced by kappa receptor ac-

tivation and antagonistic properties are due

to action on mu receptor which antagonizes

all morphine actions (mainly reverses the

analgesia and respiratory depression). It is

used mainly in the treatment of acute mor-

phine poisoning.

NALBUPHINE

It is a strong kappa receptor agonist and

mu receptor antagonist. Its agonistic prop-

erty is approximately three to four times

more than pentazocine and its antagonistic

property is approximately 10 times more

than pentazocine. It has less abuse liability

in comparison to pentazocine. It is useful

in postoperative pain, myocardial infarction

and labour.

BUPRENORPHINE

It is a potent and long acting opioid with

partial mu receptor agonist property. 25

times more potent than morphine. Effects

are similar to morphine but constipation is

less marked. It undergoes extensive

presystemic elimination and therefore is

Table 2.3.2: Classification of opioid agonists and/or antagonists.

I. Agonists-antagonists

Pentazocine (PENTAWIN) 30-60 mg/day IM/SC (used as analgesic; 50-100

mg oral)

Nalorphine (LETHIDRONE) 2-5 mg IM/IV (not used as analgesic)

Nalbuphine 10-20 mg/day SC/IM/IV

The other compounds which are agonist-antagonist are levallorphan and cyclazocine which are not used

as analgesics.

II. Partial/weak agonists

Buprenorphine (TIDIGESIC) 0.2-0.4 mg TDS SL, 0.3-0.6 mg/day IM/slow IV

Butorphanol 1-4 mg/day IM/IV

III.Pure antagonists

Naloxone (NARCOTAN) 0.4-0.8 mg/day IM/IV

Naltrexone (NALTIMA) 50-100 mg/day

Nalmefene 0.1-1.0 mg/day IM/IV