Study guide: Morphine and Synthetic Opioids

📋 Course Outline

1. Opioid Pharmacodynamics and Effects
2. Morphine Properties and Use
3. Synthetic Opioid Comparisons
4. Contraindications and Monitoring
5. Adverse Effects and Dependence

📖 1. Opioid Pharmacodynamics and Effects

★ Must-know

• Opioids produce intense, constant, dose-dependent analgesia and act on all types of pain.

• Inhibitory opioid effects include analgesia, respiratory depression, and somnolence; excitatory effects include miosis, nausea, and vomiting.

• Opioids depress respiratory responses to hypoxia and hypercapnia and impair regulation of respiratory rate; the source also notes increased tidal volume and decreased respiratory rate.

Further detail

• Opioids can cause psychomotor excitation or sedation, and psychoaffective effects ranging from euphoria to dysphoria, anxiety, hallucinations, or logorrhea.

• Opioids reduce vigilance but do not produce hypnosis.

• Opioids can cause thoracic rigidity by decreasing thoracic compliance.

💡 Memory Hook

Opioids inhibit pain and breathing, while exciting pathways can produce miosis, nausea, and vomiting.

📖 2. Morphine Properties and Use

★ Must-know

• Morphine is administered as a titrated 2 mg bolus every 5 minutes.

• Intravenous morphine begins acting after 15 minutes, reaches maximum effect after 20–30 minutes, and acts for 2–3 hours, with residual effect reported up to 4 hours.

Further detail

• A morphine ampoule contains 10 mg in 1 ml.

• Morphine is eliminated through:

  • the kidneys
  • milk
  • bile
  • stools

• Morphine is indicated for postoperative analgesia.

📖 3. Synthetic Opioid Comparisons

★ Must-know

📌 Alfentanil is listed as 30 times as potent as morphine, fentanyl as 50–100 times, and remifentanil as 300 times; the source also lists sufentanil but gives no potency figure for it.

• The source gives induction doses of 5–10 μg/kg for alfentanil, 3–5 μg/kg for fentanyl, 0.5–1 μg/kg for remifentanil over 1 minute, and 0.2–0.5 μg/kg for sufentanil.

• The listed durations are 7–10 minutes for alfentanil, 20–30 minutes for fentanyl, under 10 minutes for remifentanil, and 30 minutes for sufentanil.

Further detail

• Alfentanil, fentanyl, and sufentanil are listed as hepatically metabolized; remifentanil is metabolized by plasma esterases.

• The source lists renal elimination for alfentanil, fentanyl, remifentanil, and sufentanil.

• The source gives maintenance doses of 2.5–10 μg/kg for alfentanil, 1–3 μg/kg for fentanyl, and 0.25–0.5 μg/kg/min for remifentanil by syringe pump.

• The listed onset times are 10 seconds for alfentanil, 30 seconds to 1 minute for fentanyl, under 30 seconds for remifentanil, and 20 seconds for sufentanil.

• Fentanyl and sufentanil can be administered epidurally, and the source also lists intramuscular and subcutaneous administration for fentanyl.

• Remifentanil is very liposoluble, with a short delay and possible syringe-pump administration, but does not show clinically significant accumulation during prolonged infusion.

• The source describes sufentanil as less respiratory-depressant than fentanyl and as having low histamine release.

• The source advises calculating the dose using theoretical body weight in obese patients.

📖 4. Contraindications and Monitoring

★ Must-know

• Listed contraindications include: respiratory insufficiency, renal insufficiency, hepatic insufficiency, asthma, age under 30 months, convulsive state, acute alcohol intoxication, delirium tremens, coma, head trauma or intracranial hypertension because of hypoventilation

• Monitoring includes: respiratory rate, central nervous system depression and sedation level, analgesia and pain level, adverse effects

• Naloxone (Narcan) is listed as the opioid antidote.

Further detail

• Morphine is contraindicated at the end of pregnancy.

📖 5. Adverse Effects and Dependence

🔑 Key Concepts & Definitions

• Psychological dependence: Psychological dependence, also called addiction in the source, is dependence of a psychological nature.

★ Must-know

• Reported effects include:
  • nausea
  • vomiting
  • constipation
  • increased biliary tract pressure
  • urinary retention
  • miosis

📌 Tolerance or habituation means that progressively larger doses are needed for the same effect, whereas physical dependence is evidenced by withdrawal after treatment stops.

Further detail

• Opioids can reduce intraocular pressure, cause bronchoconstriction, and depress the cough reflex.

• Morphine is associated with marked histamine release, which is dose-dependent; the source also notes pruritus and headaches.

• The source describes morphine as causing moderate bradycardia and hypotension with good hemodynamic stability, while fentanyl is associated with a marked decrease in heart rate and a 15–20% decrease in blood pressure.

📊 Synthesis Tables

Synthetic Opioid Profiles