Intramuscular drug administration

Parenteral drug administration means the giving of a drug by the subcutaneous (SC), intramuscular (IM), intravenous (IV), or intradermal route (Fig. 2-5). Other routes of parenteral administration that may be used by the primary care provider are intralesional (into a lesion), intra-arterial (into an artery), intracardiac (into the heart), and intra-articular (into a joint), hi some instances, intra-arterial dragp are administered by a nurse. However, administration is not by direct arterial injection but by means of a catheter that has been placed in an artery. 

Ohsawa, T., Matsukawa, Y., Takakura, Y., Hashida, M., and Sezaki, H. (1985). Fate of lipid and encapsulated drug after intramuscular administration of liposomes prepared by the freezethawing method in rats, Chem. Pharm. Bull., 5013-5022. 

Avoid the subcutaneous and intramuscular route of drug administration in patients in any form of shock... 

ACTH, adrenocorticotropic hormone or corticotropin FDA, Food and Drug Administration HPA, hypothalamic-pituitary-adrenal IV, intravenously. aThe 250 meg dose has also been administered intramuscularly in an outpatient setting. The 1 meg dose is not FDA-approved. 

Parenteral administration of drugs by intravenous (IV), intramuscular (IM), or subcutaneous (SC) routes is now an established and essential part of medical practice. Advantages for parenterally administered drugs include the following rapid onset, predictable effect, predictable and nearly complete bioavailability, and avoidance of the gastrointestinal (GI) tract and, hence, the problems of variable absorption, drug inactivation, and GI distress. In addition, the parenteral route provides reliable drug administration in very ill or comatose patients. 

Ballard, B.E. (1968). Biopharmaceutical considerations in subcutaneous and intramuscular drug administration. J. Pharm. Sci 57 357-378. 

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). 

Heparin is prescribed on a unit (lU) rather than milligram basis. Tlie dose must be determined on an individual basis. Heparin is not absorbed after oral administration and therefore must be given parenterally. Intravenous administration results in an almost immediate anticoagulant effect. There is an approximate 2-hour delay in onset of drug action after subcutaneous administration. Intramuscular injection of heparin is to be avoided because of unpredictable absorption rates, local bleeding, and irritation. Heparin is not bound to plasma proteins or secreted into breast mUk, and it does not cross the placenta. 

Note Doses are provided as general guidelines only, and are not meant to be definitive. All doses must be individualized and monitored through appropriate clinical and/or laboratory means. ADHD, attention-deficit hyperactivity disorder bid, twice daily c, capsule CYP, cytochrome P450 EKG electrocardiogram FDA, Food and Drug Administration IM, intramuscular MDD, major depressive disorder OCD, obsessive-compulsive disorder PDD, pervasive developmental disorder qd, once daily qhs each bedtime qoWk, every other week t, tablet tid, three times daily TS, Tourette s syndrome WBC, white blood cell count. 

The rates of absorption, clearance, and elimination of penicillin G are further influenced by the route of administration. Intramuscular and subcutaneous injections provide drug to the bloodstream more slowly, but maintain concentrations longer than the intravenous administration. Absorption of penicillin G from intramuscular or subcutaneous sites can be further slowed down by the use of the relatively insoluble procaine salt. When equivalent dosages of penicillin G and procaine penicillin G were injected parenterally, peak residues concentration in blood occurred after 2 h and the drug had cleared the blood by 8 following penicillin G administration. With the procaine penicillin G, peak residues concentration appeared 5 h after injection and the drug cleared the plasma 24 h after administration (57). 

Following a single intramuscular injection of oxytetracycline to European eels at a dosage of 60 mg/kg bw, maximum plasma oxytetracycline concentration (113 ppm) were achieved between 8 and 16 h after administration (240). At 3 weeks after drug administration, highest residue concentrations were in liver (21.7 ppb) and bones (30.2 ppb), whereas kidney, spleen, and muscle contained 6.0, 5.5, and 3.6 ppb. This experiment demonstrated that the pharmacokinetic profile of intramuscularly injected oxytetracycline to eel differed largely from those in rainbow trout, carp, and catfish (241). 

Intramuscular. The large quantity of skeletal muscle in the body allows this route to be an easily accessible site for parenteral administration. Intramuscular injections can be used to treat a problem located directly in the injected muscle. For example, botu-linum toxin and other substances can be injected directly into hyperexcitable muscles to control certain types of muscle spasms or spasticity (see Chapter 13).7,78 Alternatively, intramuscular injection can be used as a method for a relatively steady, prolonged release of the drug into the systemic circulation to control conditions such as psychosis,2 or to administer certain vaccines. 

Most muscle relaxants are absorbed fairly easily from the gastrointestinal tract, and the oral route is the most frequent method of drug administration. In cases of severe spasms, certain drugs such as methocarbamol and orphenadrine can be injected intramuscularly or intravenously to permit a more rapid effect. Likewise, diazepam and dantrolene can be injected to treat spasticity if the situation warrants a faster onset. As discussed earlier, continuous intrathecal baclofen administration may be used in certain patients with severe spasticity, and local injection of botulinum toxin is a possible strategy for treating focal dystonias and spasticity. Metabolism of muscle relaxants is usually accomplished by hepatic microsomal enzymes and the metabolite or intact drug is excreted through the kidneys. 

Various characteristics of the molecule influence its chances of reaching its target receptor since they influence the nature and extent of the body s effect on it. A drug s pharmacokinetic profile therefore determines the extent of the drug s opportunity to exert its pharmacodynamic effect. While there are various routes for human drug administration (oral rectal intravenous, subcutaneous, intramuscular, and intra-arterial injections topical and direct inhalation into the lungs), the most common for small-molecule drugs is oral administration, and discussions in the first part of this chapter therefore focus on oral administration. (In contrast, biopharmaceuticals are typically administered by injection, often directly into the bloodstream.)... 

As indicated in Table 2.1, drugs may be injected into veins, muscles, subcutaneous tissue, arteries, or into the subarachnoid space of the spinal canal (intrathecal). For obvious reasons, intraarterial and intrathecal injections are reserved for specialized drug administration requirements, such as regional perfusion of a tumor with a toxic drug or induction of spinal anesthesia, respectively. Therefore, the more routine injection routes are intravenous (IV), intramuscular (IM), and subcutaneous (SC). Because these three modalities involve skin puncture, they carry the risks of infection, pain, and local irritation. 

Commonly used routes of drug administration. (IV=intravenous IM=intramuscular SC= subcutaneous). 

After the clinician has selected a drug for use, he or she needs to determine which route(s) of administration will best ensure a therapeutic concentration at the site of infection. For different types of ocular infection, topical application, oral administration, intramuscular injection, intravenous injection, intravitreal injection, or a combination of routes may be appropriate (Table 11-1). 

Local delivery Subcutaneously or intramuscularly applied microparticles can maintain a therapeutically effective concentration at the site of action for a desirable duration. The local delivery system obviates systemic drug administration for local therapeutic effects and can reduce the related... 

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