Introduction
Penicillin is used to refer to a group of beta-lactam antibiotics that originate from a fungus known as penicillium. The use of penicillin is largely restricted to the treatment of gram-negative bacteria. Penicillium is responsible for the production of penicillin. The production process involves oxidative stress and has been made artificial for purpose of commercial production of the drug. There are a variety of drugs that fall under the penicillin group. They include penicillin G, penicillin benzathine, penicillin V, and penicillin procaine. Penicillin was discovered in the early 1940s and become the first drug to treat diseases that were said to be caused by bacteria. The antibiotics continue to be extensively used at the moment, even though a number of bacteria have developed resistance towards the antibiotics (Levy 5). This article focuses on particular penicillin known as penicillin G benzathine.
Penicillin G benzathine is a first-generation penicillin antibiotic, also known as benzathine benzylpenicillin that is indicated as a therapy for rheumatic fever prophylaxis and early/latent syphilis, both in children as well as the adults (Hook, Stephens, and Ennis 436). Other names include Extencilline, Benzethacil Tardocillin, Debecillin, Pendepon, Penidural, and Benzacillin Cepacilina. Its molecular formula is C48H56N6O8S2 and has a molecular weight of 909.12364 (Kiddugavu et al. 2). The main structural characteristic is the presence of the four-membered ring of β-lactam. This is critical to the antibacterial activity of penicillin. The β-lactam ring is joined to a five-membered ring of thiazolidine. This fusion makes the β-lactam more reactive by removing the resonance stabilization that is found in this kind of bond (Baker and Lonergan 243). The drug is taken into the bloodstream for hydrolysis in a very slow process.
Benzathine benzylpenicillin is normally available in generic parenteral formulations used for intravenous or intramuscular use. A suspension of penicillin G Benzathine Injectable is delivered in an ISOJECT syringe: 1,200,000 units, which are in packages of 10. For every 2mL syringe, there are 1,200,000 penicillin G benzathine units; 0.0l2 grams of sodium citrate; 0.006 grams of polyvinylpyrrolidone; 0.020 grams of lecithin, plus 0.006 grams sodium carboxymethyl cellulose. Preservatives that are normally used with this drug include Methylparaben (0.09%) and Propylparaben (0.01 %.). The product is stored between 2°–8°C (36°–46°F) and should not be frozen. Normally penicillin G that is administered intravenously is given in doses of 300,000 to 4 million units per six to eight hours. When administered intramuscularly, it is given in a single dose of 2.4 million units, particularly as a therapy for primary or secondary syphilis, as well as in three doses per week for syphilis that has taken a long duration (BICILLIN L-A par. 6-10)
Penicillin G benzathine is prepared by mixing the penicillin G sodium salt with N, N’ dibenzylethylenediamine. Penicillin G can be biosynthesized in three major steps: First, the amino acid L-valine is subjected to epimerization to produce D-valine. The three amino acids (L-α-aminoadipic acid, L-cysteine, and L-valine (which is now D-valine) are then condensed into a tripeptide known as δ-(L-α-aminoadipyl)-L-cysteine-D-valine (ACV). The ACV is acted up to form isopenicillin N via oxidation.
How the drug acts
Any bacterium that is responsive to penicillin G is killed by the drug before it multiplies. Thus, the drug can be said to be bacteriocidal (Silverthorn 356). The antibiotic inhibits the cell-wall mucopeptide biosynthesis. Under normal circumstances, all bacteria normally remodel their cell walls regularly, as well as build up and break down some parts of the cell wall concurrently in the course of their growth and division (Peter and Dudley 588). The alteration comprises the breakdown of β-linked N-acetylmuramic acid plus the N-acetylglucosamine and the breakdown of the cross-linking chains peptide on the cell wall. The cross-linking chains of peptides ensure cell wall rigidity. The peptide cross-link breakdown is facilitated by the transpeptidase enzyme; this is the same enzyme that also aids the peptide bonds reformation after cell wall restructuring (Mahoney et al. 63).
Once brought into contact, the four-membered β-lactam ring of the Penicillin G binds to the DD-transpeptidase enzyme, which ultimately renders it incapable of catalyzing the formation of the cell wall cross-links of peptidoglycan (Baker and Lonergan 246). Despite this inhibition, the enzyme that is responsible for the hydrolysis of the peptidoglycan cross-links keeps functioning. This, in turn, leads to an imbalance between cell wall build-up and breakdown, thus leading to rapid death of the cell. Initial forms of peptidoglycan cause the enzymes responsible for hydrolysis to be more active. This causes the bacteria to break their cell walls through self-lysis (Peter and Dudley 590). Penicillin is small in size. This enables the drug to penetrate the entire cell wall depth, thereby increasing its potency (Mahoney et al. 64).
Penicillin G benzathine exerts high activity against streptococci, pneumococci and staphylococci, except those that produce penicillinase enzyme. Other organisms that react with penicillin G include N. gonorrhoeae, B. anthracis, Clostridia, A. bovis, L. monocytogenes, and Leptospira, among others. T. pallidum is particularly very sensitive to penicillin G. Penicillin G is, however, not active against bacteria that produce penicillinase enzyme, like many staphylococci strains.
Pharmacokinetics
There is slow uptake of the benzathine form of the drug when the drug is given through the IM route. The drug is hydrolyzed to form penicillin G. However, it is more prolonged compared to other parenteral penicillins. Administering the drug through injection into the muscle sees the drug reach its peak in the blood in about 180 minutes. The IV route sees the drug reach its peak once infusion is over. About 60% of penicillin G binds to serum protein drugs and then circulates through the body tissues in varying quantities. The largest quantities of the drug are deposited in the renal system, mainly the kidneys. The drug’s presence in other organs like the skin is only at minimal levels. It is very hard to find penicillin G crossing the blood-brain barrier, thus the CSF records very low levels of the drug. Healthy kidneys eliminate penicillin G effectively. However, slow elimination is significantly experienced in neonates, infants, as well as adults with compromised kidneys (Mahoney et al. 66).
When to use and when to avoid penicillin G treatment
Bacterial infections that involve bacterial that is responsive to penicillin G are well countered by this drug. Moreover, any bacteria that cannot tolerate the drug even at its lower levels or due to long exposure to the drug is cured well using this drug. It is always advisable to conducts tests of sensitivity before commencing treatment. The physician should also be guided by clinical adverse effects reported by the patient before deciding to use the drug. Several infections can react to adequate doses of Penicillin G benzathine. They include infections by streptococcus (Group A bacteremia), mild/moderate upper respiratory tract infections like pharyngitis, and venereal infections like syphilis, pintayaws, as well as bejel. This drug finds use in rheumatic fever treatment whereby it is used to prevent the occurrence of the fever. Taking the drug is an effective way of preventing rheumatic fever from recurring. The drug also finds use in the prophylaxis of rheumatic heart disease. Inflammation of the glomerulus is also well controlled by administering penicillin G.
It is advisable not to use penicillin G in patients who have a past experience of hypersensitivity to penicillin, regardless of the specific penicillin. It is, therefore, important for judicious investigation regarding the previous hypersensitivity to penicillins to be conducted before therapy is initiated. Penicillin G should be immediately discontinued where an allergy is noted (Peter and Dudley 587).
Drug interactions
It is not advisable to use penicillin G in combination with tetracycline because both drugs cancel each other’s effects. It is also advisable not to use the drug together with probenecid therapy because it leads to retention of penicillin G in the body for longer. This may lead to toxicity. Moreover, penicillins interfere with glycosuria test. However such reactions have not been reported in the glucose oxidase method (James and Gurk-Turner 106-107).
Side effects
Besides the desired effects of penicillin G, some unwanted effects may accompany its action. It calls for medical attention when they occur. Some of the major adverse reactions resulting from this disease include mild diarrhea, nausea and urtica. Muscle pain, difficulty in breathing, rashes, fast heartbeat, and hallucinations, among others are also observed. Super infections like candidiasis may also occur. In addition, some less common adverse effects including fever, pseudomembranous colitis, vomiting, worsening arthritis, dermatitis and angioedema, seizures like in epileptics may also occur. Administering penicillin G is said to cause some mental side effects associated with the temporal lobe. They include being nervous and being confused. The urinary system may become diseased to the level of experiencing renal failure. Creatinine levels in the blood are reported to shoot up following the use of the drug.
Pain, bleeding and inflammations are major experiences at the injection site as penicillin G is majorly administered parenterally. Penicillins report the commonest allergy. In reality, it is the common cause of a number of allergic reactions. However, it is important to note that less than a fifth of the reported allergy cases are truly allergic to penicillin. The major allergic reactions include itching, chest tightness, hives, and swelling of the tongue, the face and mouth, among others. It has been estimated that 10% of the patients who receive any beta-lactam antibiotic will experience allergic reactions, while 0.01% will experience anaphylaxis.
It is advisable that drug administration should be stopped immediately and medical attention sought once such adverse effects are experienced. Some side effects that accompany the drug may not need medical attention because they subside in the course of the treatment, while the body adapts to the medication.
Symptoms and management of overdoses
Overdoses of penicillin G benzathine have not been reported. It is rare to find penicillins being toxic to cells of the human being. Nevertheless, it is possible to have penicillin G cause neurovascular problems. Given that there is no treatment to reverse the toxic effects, the treatment should focus on curing the symptoms that are present. An initial 0.5 milligrams of HCl may be administered subcutaneously or intramuscularly followed by a repeated intravenous dose of 0.025-0.05 milligrams after every 5-15 minutes in cases of anaphylactic shock in adults. In children, an initial 0.01 mg/kg epinephrine HCl should be administered subcutaneously and then repeated every 20 minutes to four hours depending on the severity, as well as the patient reaction (NCBI par. 11).
The use of penicillin G benzathine, as well as other penicillin drugs, is legal and has not had any illegal indications, but it is to be used by professionals only under prescription. It is, therefore, illegal to get the drug by any other means, except by prescription. This is majorly due to the ever-increasing antibiotic resistance incidences that have presented a major challenge to treat with antibiotics (Galvao et al. 146). Penicillin G is supplied in formulations for intramuscular and intravenous use. The use of this medication should be directed by laboratory tests, including sensitivity testing as well as clinical indications (Levy 5). Only aqueous penicillin G should be used for intravenous administration. The physician’s advice and the help of pharmacists should be strictly followed for optimal health results (NCBI par. 6). When used in the right manner, penicillin G benzathine has proven to be a very effective and essential antibiotic against the treatment of and the prevention of group A streptococcal infections that are associated with rheumatic fever, as well as rheumatic heart disease. It is also an effective and safe drug for managing syphilis (Galvao et. al. 123).
Works Cited
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