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Codeine


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Codeine is an opiate used to treat pain, as a cough medicine, and for diarrhea. It is typically used to treat mild to moderate degrees of pain. Greater benefit may occur when combined with paracetamol (acetaminophen) or a nonsteroidal anti-inflammatory drug (NSAID) such as aspirin or ibuprofen. 

Evidence does not support its use for acute cough suppression in children or adults.  In Europe it is not recommended as a cough medicine in those under twelve years of age. It is generally taken by mouth. It typically starts working after half an hour with maximum effect at two hours. Its effects last for about four to six hours
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Indication

For treatment and management of pain (systemic). It is also used as an antidiarrheal and as a cough suppressant. Codeine is also used to treat diarrhea and diarrhea-predominant irritable bowel syndrome, although loperamide (which is available without a prescription for milder diarrhea), diphenoxylate, paregoric or even laudanum are more frequently used to treat severe diarrhea.

There is weak evidence that it is useful in cancer pain but it is associated with increased side effects. The American Academy of Pediatrics does not recommend its use in children due to side effects. The FDA lists age under 12 years old as a contraindication to use.

Furthermore, codeine has been found as an endogenous compound, along with morphine, in the brains of non-human primates with depolarized neurons, indicating that codeine may function as a neurotransmitter or neuromodulator in the central nervous system.

Mechanism of action

Opiate receptors are coupled with G-protein receptors and function as both positive and negative regulators of synaptic transmission via G-proteins that activate effector proteins. Binding of the opiate stimulates the exchange of GTP for GDP on the G-protein complex. 

As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine and noradrenaline is inhibited. Opioids also inhibit the release of vasopressin, somatostatin, insulin and glucagon. Codeine's analgesic activity is, most likely, due to its conversion to morphine. 

Opioids close N-type voltage-operated calcium channels (OP2-receptor agonist) and open calcium-dependent inwardly rectifying potassium channels (OP3 and OP1 receptor agonist). This results in hyperpolarization and reduced neuronal excitability.

Absorption
Well absorbed following oral administration with a bioavailability of approximately 90%. Maximum plasma concentration occurs 60 minutes post-administration. Food does not affect the rate or extent of absorption of codeine.
Volume of distribution
Apparent volume of distribution = 3-6 L/kg
Protein binding
7-25% bound to plasma proteins.

Route of elimination
90% of the total dose of codeine is excreted through the kidneys, of which 10% is unchanged codeine.
Half life
Plasma half-lives of codeine and its metabolites have been reported to be approximately 3 hours.



Codeine Warnings

You shouldn’t take codeine if you're allergic to it (or to any other ingredients in the drug) or have trouble breathing.
If you experience any of the following after starting codeine, talk to your doctor, as you may be allergic to the drug:
·         Itching
·         Rash
·         Hives
Before taking codeine, tell you doctor if you have:
·         Kidney or liver problems
·         Seizures
    Problems with your stomach or intestines, including a blockage in your intestinal tract and inflammatory bowel disease
·         Addison’s disease
·         An enlarged prostate
·         Had a recent head injury

Common Side effects of Codeine
  • Dry mouth
  • Racing heart beat
  • Changes in your vision
  • Constipation
  • Nausea and vomiting
  • Stomach pain
  • Dizziness and drowsiness
  • Headache
  • Sweating
Serious Side Effects of Codeine
  • Very slow heartbeat and a weak pulse
  • Low blood pressure
  • Seizures
  • Shallow breathing
  • Mood changes or mental disturbances, such as hallucinations, irritability, and confusion
  • Dependence on the drug
  • Intestinal blockage
  • Shock
  • Cardiac arrest, or heart abruptly stops beating
Codeine Interactions
Tell your doctor and pharmacist about any drugs you're taking.
This includes prescription and over-the-counter medications, vitamins and other dietary supplements (nutritional shakes, protein powders, etc.), herbal remedies, and any illegal and recreational drugs.
Avoid taking codeine if you are also taking the following drugs:
  • Amiodarone (Cordarone)
  • Imatinib (Gleevec)
  • Antihistamines, such as doxylamine (Unisom), diphenhydramine (Benadryl), and chlorpheniramine (Chlor-Trimeton)
  • Potassium phosphate/sodium phosphate (K-Phos) and potassium citrate (Urocit-K)
  • HIV/AIDS drugs, such as ritonavir (Norvir) and tipranavir (Aptivus)
  • Propafenone (Rhythmol)
Codeine and Alcohol
Both alcohol and codeine dull the senses, cause confusion, and slow breathing, and taking the two together could worsen these effects.
Avoid drinking alcohol while taking codeine.

Codeine Overdose
Symptoms of a codeine overdose may include:
  • Slow or shallow breathing
  • Blue-colored fingernails or lips
  • Dizziness, confusion, or fatigue
  • Cool, clammy skin
  • Loss of consciousness
  • Pinpoint pupils
Missed Dose of Codeine
Unless your doctor’s told you otherwise, you should generally take codeine only when you need it, so missing a dose shouldn’t be an issue.
However, if your doctor did tell you to take codeine regularly, and you realized that you’ve missed a dose of codeine, try to take it as soon as possible.
If it’s almost time for your next dose, skip the missed dose and take your next dose like you normally would.
Don’t take two doses of the medication at the same time

Codeine Codeine Reviewed by gafacom on June 01, 2019 Rating: 5

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