Where is codeine absorbed

Dissolution, if slower than absorption, becomes the rate-limiting step. Eur J Pharm Sci , Drugs given IV enter the systemic circulation directly.

However, drugs injected IM or subcutaneously sc must cross one or more biologic membranes to reach the systemic circulation. In such cases, drug delivery to systemic circulation is slow and often incomplete because of first-pass metabolism metabolism of a drug before it reaches systemic circulation by proteolytic enzymes in the lymphatics. Thus, injection site can affect absorption rate. Absorption after IM or sc injection may be delayed or erratic for salts of poorly soluble bases and acids eg, parenteral form of phenytoin and in patients with poor peripheral perfusion eg, during hypotension or shock.

Controlled-release forms are designed to reduce dosing frequency for drugs with a short elimination half-life and duration of effect. These forms also limit fluctuation in plasma drug concentration, providing a more uniform therapeutic effect while minimizing adverse effects.

Absorption rate is slowed by coating drug particles with wax or other water-insoluble material, by embedding the drug in a matrix that releases it slowly during transit through the gastrointestinal tract, or by complexing the drug with ion-exchange resins. Most absorption of these forms occurs in the large intestine. Crushing or otherwise disturbing a controlled-release tablet or capsule can often be dangerous.

Transdermal controlled-release forms are designed to release the drug for extended periods, sometimes for several days. Drugs for transdermal delivery must have suitable skin-penetration characteristics and high potency because the penetration rate and area of application are limited. Many non-IV parenteral forms are designed to sustain plasma drug concentrations. Absorption of antimicrobials can be extended by using their relatively insoluble salt form eg, penicillin G benzathine injected IM.

For other drugs, suspensions or solutions in nonaqueous vehicles eg, crystalline suspensions for insulin are designed to delay absorption. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world.

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Oral Administration. General reference. Parenteral Administration. Controlled-Release Forms. Infants and young children metabolise codeine to morphine. A study after single and repeated rectal administration. Br J Clin Pharmacol ; 33 : 45 —9. Complementary and synergistic antinociceptive interaction between the enantiomers of tramadol.

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Pharmacology of codeine 37 Dosage and uses. Codeine phosphate in paediatric medicine. Williams , D. Oxford Academic. Google Scholar. Cite Cite D. Select Format Select format. Abstract Br J Anaesth ; 86 : — Open in new tab Download slide. Fig 1 World Health Organization analgesic ladder. Fig 2 The chemical structure of codeine.

Fig 3 Metabolism of codeine. Table 1 Side effects of codeine. Open in new tab. September Online Mendelian Inheritance In Man J Pharmacol Exp Ther. J Neurochem. Eur J Clin Pharmacol. Pharmacol Rev. Ther Drug Monit. Clin Pharmacol Ther. Clin Invest. Genet Epidemiol. J Natl Cancer Inst. Life Sci. Br J Clin Pharmacol. Swed Dent J. Biochem Biophys Res Commun. Eur J Drug Metab Pharmacokinet.

Edinburgh: Churchill Livingstone, Acta Anesth Scand. J Med Genet. Am J Hum Genet. Clin Trials J. Proc Finn Dent Soc.

London: Edward Arnold, J Clin Pharmacol. Edingburgh: Churchill Livingstone, Clin Otalaryngol. Clin Exp Pharmac Physiol.

Dev Pharmacol Ther. J Am Geriatr Soc. J Biol Chem. Can J Physiol Pharmacol. Br J Cancer. Br J Anaesth. Crit Care Med. Paediatr Anaesth. Am J Dis Child. Biochem Pharmacol. S Afr Med J. It can cause intense skin irritation. The main difficulty regularly reported, other than dependence, is that codeine, is that it is painfully constipating and can suppress the libido. Codeine is also available combined with Ibuprofen; a common formulation is Under the Misuse of Drugs Act and the Prescription Only Medicines Human Use Order , there are provisions for small quantities of these controlled drugs to be included in non-prescription medicines and sold through pharmacies only.

They may include doses of up to Pharmacology Codeine is selective for the mu receptor, but with a much weaker affinity than morphine. Share Facebook Twitter.