Intramuscular injection preparations

Yoshida, A., Yamamoto, M., Itoh, T. et al. Utility of 2-hydroxypro-pyl-P-cyclodextrin in an intramuscular injectable preparation of nimodipine. Chem. Pharm. Bull. 1990, 38, 176-179. 

The provision of fat-soluble vitamins and lipids is difficult, if not impossible, in various diseases. This is especially true for diseases that are accompanied by a lot of oxidative stress, for example, mucoviscidosis. The requirements of fat-soluble antioxidative substances are certainly high in these cases and can barely be covered by intramuscular injections because fat-soluble vitamins can hardly, if at all, be absorbed from oily preparations. Alternatively, the vitamins can administered via the buccal mucosa the fat-soluble substances have to be packaged in such a way that they can be transported in a watery compartment and are thus able to largely dissolve in the saliva. When they have an adequate size, they can then penetrate the buccal mucosa. One approach is the development of the so-called nanocolloids, that is, particles with a polar nucleus, in which the fat-soluble vitamin is dissolved, and an apolar wrapping (monolayer). This structure makes an oral application of fat-soluble substances possible. First tests demonstrated that vitamin A palmitate, a-tocopherol, as well as coenzyme Qio are thus able to enter the systemic circulation via the buccal mucosa. 

The emetines include emetine and dehydroemetine. These drugs act only against trophozoites. Their mechanism of action is based on eukaryote protein synthesis. They are parenterally administered because oral preparations are absorbed erratically and may induce severe vomiting. They are widely distributed and accumulate in liver, lungs and other tissues. The emetines are slowly elimination via the kidneys. Local side-effects in the area of the intramuscular injection are pain, tenderness and muscle weakness. Serious toxicity is common if the drugs are given for more than 10 days. Side effects include nausea, vomiting, diarrhoea but also cardiotoxicity. 

Glucocorticoids are available in a wide range of preparations, so that they can be administered parenterally, orally, topically, or by inhalation. Obviously the oral route is preferred for prolonged therapy. However, parenteral administration is required in certain circumstances. Intramuscular injection of a water-soluble ester (phosphate or succinate) formed by esterification of the C21 steroid alcohol produces peak plasma steroid levels within 1 hour. Such preparations are useful in emergencies. By contrast, acetate and tertiary butylacetate esters must be injected locally as suspensions and are slowly absorbed from the injection site, which prolongs their effectiveness to approximately 8 hours. 

Parenteral administration This route is applicable for drugs which are inactivated by gastrointestinal tract or absorption is poor when given orally or there is a urgency for fast response in small dose. Intramuscular, intravenous, or subcutaneous routes are commonly used. The intravenous injection (in aqueous solution) is introduced directly into the vein by which a rapid response is produced. The subcutaneous injection are given through the layer of skin, while intramuscular injection, introduced through the skin layer deep into the muscle. The nature of intramuscular injection may be in aqueous or oily solution/suspension form. The aqueous solution will be rapidly absorbed as compared to oily solution or suspension. So, the rate of absorption is dependent on the nature of the preparation. 

All three hormones—FSH, LH, and hCG—are heterodimers that share an identical a chain in addition to a distinct chain that confers receptor specificity. The 13 chains of hCG and LH are nearly identical, and these two hormones are used interchangeably. All the gonadotropin preparations are administered by subcutaneous or intramuscular injection, usually on a daily basis. Half-lives vary by preparation and route of injection from 10 to 40 hours. 

Only one implantable contraceptive preparation is available at present in the USA. Etonogestrel, also used in some oral contraceptives, is available in the subcutaneous implant form listed in Table 40-3. Several hormonal contraceptives are available as vaginal rings or intrauterine devices. Intramuscular injection of large doses of medroxyprogesterone also provides contraception of long duration. 

The activity of penicillin G was originally defined in units. Crystalline sodium penicillin G contains approximately 1600 units per mg (1 unit = 0.6 meg 1 million units of penicillin = 0.6 g). Semisynthetic penicillins are prescribed by weight rather than units. The minimum inhibitory concentration (MIC) of any penicillin (or other antimicrobial) is usually given in mcg/mL. Most penicillins are dispensed as the sodium or potassium salt of the free acid. Potassium penicillin G contains about 1.7 mEq of K+ per million units of penicillin (2.8 mEq/g). Nafcillin contains Na +, 2.8 mEq/g. Procaine salts and benzathine salts of penicillin G provide repository forms for intramuscular injection. In dry crystalline form, penicillin salts are stable for years at 4°C. Solutions lose their activity rapidly (eg, 24 hours at 20°C) and must be prepared fresh for administration. 

Tiaprofenic acid is a racemate and given as oral or rectal preparations (600 mg/day) and as an intramuscular injection of the trometamol salt. 

Leuprolide is available in solution for daily subcutaneous injection and in slow-release depot preparations in which leuprolide is lyophilized in microspheres given by intramuscular injection. 

Procaine salts and benzathine salts of penicillin G provide repository forms for intramuscular injection. In dry crystalline form, penicillin salts are stable for long periods (eg, for years at 4 °C). Solutions lose their activity rapidly (eg, 24 hours at 20 °C) and must be prepared fresh for administration. 

The most important action is to ensure that the client receives appropriate pharmacological treatment. One of the main problems in schizophrenia is lack of medication compliance. This is often caused by lack of client collaboration, often explained by the intrinsic pathological characteristics of the disease itself. Both typical and atypical depot antipsychotics formulations are available. Depot preparations are typically administered by intramuscular injection every 1-4 weeks. This may be of great advantage in patients with poor compliance. 

Human tetanus immunoglobulin is a solution of human immunoglobulin G (IgG) containing a high level of anti-tetanus toxin antibodies. It is prepared from the plasma of screened, human donors immunised against tetanus toxin and is administered by intramuscular injection. The product also contains isotonic sodium chloride, glycine, as a stabiliser, sodium acetate and a small amount of sodium hydroxide used to maintain pH. The product is generally well-tolerated. 

Therapeutic formulations contain a recombinant form of IFN-a (either interferon alfa-2a or interferon alfa-2b). These are available as powders for reconstitution or as prefilled injection pens. The drug is administered by subcutaneous injection (or intravenous for reconstituted powder formulations) and intramuscular injection. The dosage is usually stated as units per millilitre (refer to BNF for various preparations and dosages). Powder formulations of interferon alfa-2b also contain glycine, sodium phosphate (mono- and dibasic) and human albumin prefilled pens contain sodium chloride, edetate disodium, polysorbate 80 and m-cresol as a preservative. 

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