Blood intramuscular/subcutaneous

After IV injection, the drug is delivered immediately and totally into the blood (100% bioavailability). In contrast, a drug administered via any other route (intramuscular, subcutaneous, intestinal, rectal, buccal, sublingual, nasal, pulmonary and vaginal) will have to circumvent various physical and chemical barriers (discussed below), so that the bioavailability will be lower in comparison to that obtained after iv administration. For example, to achieve 100% bioavailability via the oral route requires the drug to ... 

Phytonadione is used to treat vitamin K deficiency. The dose, frequency, and duration of vitamin K depend on the severity of the deficiency and the patient s response. Vitamin K may be administered orally, intramuscularly, subcutaneously, or intravenously. After an oral dose of vitamin Kj, the blood coagulation factors increase within 6 to 12 hours. When administered parenterally, the PT may take 12 to 24 hours to normalize, although improvement usually occurs within 1 to 2 hours. Failure to correct the PT after 48 hours should raise suspicion aboutthe etiology of the coagulation abnormality (e.g., liver disease). 

The nurse obtains the blood pressure, pulse, and respiratory rate 20 to 30 minutes after the drug is administered intramuscularly or subcutaneously, 30 or more minutes if the drug is given orally, and in 5 to 10 minutes if the drug is given intravenously (IV). 

Opioids are easily absorbed subcutaneously and intramuscularly, as well as from the gastrointestinal tract, nasal mucosa (e.g., when heroin is used as snuff), and lung (e.g., when opium is smoked). About 90% of the excretion of morphine occurs during the first 24 hours, but traces are detectable in urine for more than 48 hours. Heroin (diacetyhnorphine) is hydrolyzed to monoacetylmorphine, which is then hydrolyzed to morphine. Morphine and monoacetylmorphine are responsible for the pharmacologic effects of heroin. Heroin produces effects more rapidly than morphine because it is more lipid soluble and therefore crosses the blood-brain barrier faster. In the urine, heroin is detected as free morphine and morphine glucuronide (Gutstein and Akil 2001 Jaffe et al. 2004). 

Some types of injections must be made iso-osmotic with blood serum. This applies particularly to large-volume intravenous infusions if at all possible hypotonic solutions cause lysis of red blood corpuscles and thus must not be used for this purpose. Conversely, hypertonic solutions can be employed these induce shrinkage, but not lysis, of red cells which recover their shape later. Intraspinal injections must also be isotonic, and to reduce pain at the site of injection so should intramuscular and subcutaneous injections. Adjustment to isotonicity can be determined by the following methods. 

In vivo Release of Desmopressin and Somatostatin. The in vivo release of Desmopressin and Somatostatin after subcutaneous and intramuscular injections of the peptide in the cubic or the lamellar phase has been studied in the rabbit. Blood was sampled at regular intervals, and systemically absorbed Desmopressin and Somatostatin were determined as the specific immunoreactitvity in plasma of the actual peptide. For details of the analyses with dDAVP, consult ref. 9. For comparison, Desmopressin-like and Somatostatin-like immunoreactitvity (dDAVP-LI and SRIF-LI) in plasma after intravenous bolus injections of the two peptides were determined as well. 

Famphur is administered to livestock by intramuscular or subcutaneous injection, through the diet, as a dermal pour-on, or as an oral bolus. In mammals, famphur induced mortality at concentrations as low as 11.6 mg/kg BW in intraperitoneal injection (mouse), 27 mg/kg BW in a single oral exposure (mouse), >33.3 mg/kg BW in an intramuscular injection (Brahman cattle, Bos indicus), and 400 mg/kg BW in a dermal application (rat, Rattus sp.). Latent effects of famphur exposure were reported in reindeer (Rangifer tarandus) hinds 1 year posttreatment (altered blood chemistry). Famphur is rapidly metabolized by mammals. The half-time persistence of famphur and famoxon in subcutaneous fat of cattle after a single pour-on application is 0.9 days and is independent of dose between 25 and 150 mg/kg BW or initial tissue residues between 1.8 and 2.3 mg/kg BW. 

The absorption rate of drugs administered as intramuscular or subcutaneous injections may be affected in elderly because of reduced tissue blood perfusion. This is also true for transdermal administration, e.g. patches and gels, of drugs (Turnheim 2003). 

The parenteral routes include three major ones IV (intravenous), IM (intramuscular), and SC (subcutaneous) and a number of minor routes (such as intraarterial) that are not considered here. Administration by the parenteral routes raises a number of special safety concerns in addition to the usual systemic safety questions. These include irritation (vascular, muscular, or subcutaneous), pyrogenicity, blood compatibility, and sterility (Avis, 1985 Ballard, 1968). The background of each of these, along with the underlying mechanisms and factors that influence the level of occurrence of such an effect, are discussed in Chapter 11. 

Absorption is the critical factor that determines entry of an antimicrobial agent into the blood stream when an extravascular route of administration, i.e. oral, intramuscular (IM), or subcutaneous (SC) injection is used. Absorption, the extent of which depends mainly on the physicochemical properties of the antimicrobial agent, is associated with intra-mammary or intra-uterine therapy. 

Even when administered by intramuscular or subcutaneous injection the rate of absorption of drugs from their site of administration varies, not only from individual to individual, but from site to site in the same subject (B13). For the few drugs studied in this way absorption and distribution was quicker and higher blood levels achieved when injections were given into upper rather than lower limbs and proximal to the trunk than distally. 

Three forms of calcitonin are available, salmon, porcine and human calcitonin. Long-term use of porcine calcitonin, being the most antigenic product, can lead to the production of neutralizing antibodies. Synthetic salmon preparations are therefore preferable. Human calcitonin is less immunogenic but it is also less active. Human calcitonin monomer has a half-life of about 10 minutes while the half-life of salmon calcitonin is considerably longer. However these half-lives are not directly related to the duration of action which varies from 30 min to 12 hours after intravenous administration and from 8 hours to 24 hours when administered subcutaneously or intramuscularly. Calcitonin is metabolized in the blood and in tissues like for example the kidneys. 

Calcitonin is also moderately effective in Paget s disease, but requires regular subcutaneous or intramuscular injection. Mithramycin has been used with some success, but is relatively toxic, and its use requires careful monitoring of blood counts to avoid marrow suppression, so it is rarely used in current practice. 

Intramuscular and subcutaneous injections are by far the most common means of parenteral drug administration. Because of the high tissue blood flow and the ability of the injected solution to diffuse laterally, drug absorption generally is more rapid after intramuscular than after subcutaneous injection. Drug absorption from intramuscular and subcutaneous sites depends on the quantity and composition of the connective tissue, the capillary density, and the rate of vascular perfusion of the area. These factors can be influenced by the coinjection of agents that alter local blood flow (e.g., vasoconstrictors or vasodilators) or by substances that decrease tissue resistance to lateral diffusion (e.g., hyaluronidase). 

Advantages of the intramuscular and subcutaneous routes include an increased reliability and precision in the drug blood level Anally achieved and reasonably rapid absorption and onset of drug action. There are, however, serious disadvantages as well. Pain, tenderness, local tissue necrosis (primarily with highly alkaline injections), microbial contamination, and nerve damage may be associated with these forms of parenteral administration. 

In most species, chloramphenicol is rapidly and almost completely absorbed from the gastrointestinal tract. This route of administration provides antibiotic levels in blood comparable witli or higher than die intramuscular or the subcutaneous routes. The only known exception is in ruminants in which the drug is destroyed by the rumen microflora. 

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