Opioids - Analgesic Drugs

Question 1

Morphine

Answer 1

Action on :
- CNS : analgesic, sedative / excitatory, emesis, depr of resp, vasomotor and cough centres, stimulant & depr on sp.cord, myosis, euphoria, addiction.
- GI : inhibition of peristaltic mvms (-> constipation)
& incr P on ur.bladder, incr PRL/ADH/GH, incr Histamine release, incr myocardial perfusion

Dose : dogs 0,2 IM, SC
cats 0,1 SC
horse 0,1 - 0,17 IM

Question 2

Codeine

Oxycodone, Hydrocodone

Answer 2

Suppressing cough.

Cats = sensitive

Question 3

Methadone

Answer 3

Orally. Longer duration of action than Morphine.

~Morophine, but less sedative.
Use : for neuroleptanalgesia in horses & dogs (combination with Acepromazine, Chlorpromazine, Propiopromazine)

Question 4

Fentanyl

Alfentanil, Remifentanil

Answer 4

80 - 100X more potent than morphine, but short action.
Lipophilic

Use : by anaesthesiologists for neuroleptanalgesia in lab animals (combination with Fluanisone).

SE : renal toxicity, bradycardia, resp.depr.

Remifentanil, Alfentanil : faster onset, shorter half-life.

Question 5

Etorphine

Answer 5

Extremely high analgesic activity, v rapid onset & long effect.
Lipophilic
In combination for neuroleptanalgesia.
Less emetic, resp.inhibition

Question 6

Pethidine

Answer 6

Less potent.
Spasmolytic - atropine like action (colic disorders)

Dose : horse 2 (1-5) mg/kg IM, dog & cat 3 mg/kg IM.

Question 7

Butorphanol

Answer 7

~ Morphine, but effective in visceral pain, with less SE.
Alone / combo

Use :

• Horse : relief pain caused by intest torsion, impactiom, intussusceptions
• Dog & cat : analgesic, pre-anesthetic

Question 8

Tramadol

Answer 8

PO (IV), intensive metabolism

Combo with NSAIDs, anaesthetics
Indications in dogs & cats : from mild post-surgical pain - cancer pain

SE : sedation, vomiting, resp.depr (cats), dysphoria & mydriasis