Morphine is an opioid that attacks the opioid receptors at the spinal cord, medulla oblongata, the spinal trigeminal nucleus and the grey region. The receptors, which are of µ, α, β types, enhance the interaction of the drug and eventual effects in the human body. Of these receptor types, the µ is the most important for analgesia effects to be realized. There are two µ subtypes: the µ1 and the µ2 (Stoelting 1999). The µ1 subtype is involved in analgesia more than the µ2 since, the second subtype, which is involved more in the respiratory depression. In addition, the µ2 subtype is also involved in mediating bradycardia and physical dependence (Hasslesstrom & Sawe 2001).
The presence of Morphine makes the G-protein active and this is important for it to bind to the receptor. Upon being activated, the G protein alters the permeability at the neural receptors (Chay, Duff, & Walker 2002). When the permeability is affected, neuronal activity is altered through hyperpolarization of the membrane. When neuronal activities stop, analgesia is initiated (Dolin 2000). The opiate receptors at the Central Nervous System are the main areas where morphine attacks. At the brainstem centers, morphine directly affects the respiratory activities, causing respiratory depression that eventually leads to analgesia (Bhandari, Bergqvist, & Kronsberg 2005).
Respiratory depression involves reducing the receptiveness of the respiratory centers, and this inhibits reaction to carbon dioxide increase and electrical stimulation (National Center for Biotechnology Information 2011). Other than analgesia, morphine also affects the cough center, causing depression in the cough reflex. The cough center is at the medulla and morphine penetrates and causes the depression through its interaction with the opioid receptors. When morphine is given in smaller doses, antitussive effects may occur in place of analgesia (Meldrum 2003).
Orthostatic hypotension can be caused by morphine through peripheral vasodilatation. Morphine can also cause hypotension through the release of histamine. Some of the detectable features after morphine intake include histamine release, flushes, red eyes and sweating. Morphine also affects the endocrine system through hormone secretion (Anand, Hall, & Desai 2004). The drug alters the secretion of Acylcorticotropic hormone, cortical, and luteinizing hormone and this affects various body functions and activities.
Morphine also alters the immune system by reducing the secretion of various hormones responsible for enhancing immunity (Health Grades 2011). Morphine has an elimination halftime of one and a half hours to four and a half. The bolus administration makes the onset time to be slow, taking between 15 to 30 minutes. The reason for this is that morphine has a low lipid solubility of about 2.5 % of sublimaze. Morphine has a weak base of about 8 units on the pH scale and this makes it easy ionize. The ionized form inhibits the passage of the drug...