Morphine

Morphine is a painkiller from the opiate family. It acts directly on the central nervous system (CNS), reducing the sensation of pain. It can be taken for both acute and chronic pain and is often used for severe pain after heart attacks, kidney stones, and during labor. Morphine can be given by mouth, by injection into a muscle, by injection under the skin, intravenously, by injection into the space around the spinal cord, or rectally. Because opioids can cause severe dependence, morphine is only available with a narcotic prescription.

Pharmacodynamics

Morphine acts in the central nervous system on μ-, κ-, and δ-opioid receptors. Primarily by binding to μ-receptors, pain transmission in the brain is inhibited, resulting in the analgesic effect. Activation of opioid receptors disrupts presynaptic calcium influx, leading to hyperpolarization in the cell and thus decreased excitability. Postsynaptically, morphine activates potassium channels, increasing the potassium efflux. This also results in hyperpolarization and decreased excitability of the nerve cell.

Pharmacokinetics

Morphine is absorbed in the alkaline environment of the upper intestine and rectal mucosa. The bioavailability of morphine is 80-100%. Morphine is 35% protein bound in the blood. Morphine is 90% metabolized by glucuronidation through UGT2B7 and sulfation. Morphine is 90% metabolized by glucuronidation and sulfation. 70-80% of the administered dose is excreted within 48 hours. Morphine is excreted predominantly in the urine and to a lesser extent in the stool.

Side effects

Common side effects

• Constipation
• nausea or vomiting
• drowsiness
• dizziness and spinning sensation (vertigo)
• confusion
• headache
• itching or rash

Serious side effects

• difficulty breathing or short shallow breathing
• muscle stiffness
• severe dizziness and tiredness (hypeotonia)
• seizures or convulsions

If you have a seizure or convulsion, seek emergency medical attention immediately.

Toxicological Data

LD50 (rat, oral): 335 mg-kg-1