Penicillins can be classified into four broad categories, each covering a different spectrum of activity. The natural penicillins (penicillin G and penicillin V) have activity against many gram-positive organisms, gram-negative cocci, and some other gram-negative organisms. The aminopenicillins (ampicillin, amoxicilline, bacampicillin, and pivampicillin) have activity against penicillin-sensitive gram-positive bacteria, as well as Escherchia coli, Proteus mirabilis, Salmonella sp., Shigella sp. and Haemophilus influenza. The antistaphylococcal penicillins (cloxacillin, dicloxacillin, etc) are also active against beta - lactamase - producing staphylococci. The antipseudomonal penicillins have less activity against gram-positive organisms than the natural penicillins or aminopenicillins.

Benzylpenicillin can be considered the parent compound of the penicillins and is inactivated by penicillinase - producing bacteria and because of its instability in gastric acid it is usually injected. Long-acting preparations include procaine penicillin and benzanthine penicillin which slowly release benzylpenicillin after injection. Phenoxymethyl penicillin is acid - stable and therefore given by mouth but it is also inactivated by penicillinase. It is generally used for relatively mild infections.

The isoxazolyl penicillins such as cloxacillin are resistant to penicillinase and gastric acid.

Ampicillin has a broader spectrum of activity than benzylpenicillin; although generally less active against gram-positive bacteria, some gram-negative organisms including Escherichia coli. Haemophilus influenzae, and Salmonlella spp. are sensitive although resistance is being reported increasingly, Pseudomonas spp are not sensitive. Ampicillin is acid stable and can be given by mouth but is destroyed by penicillinase. Amoxycillin, only differs from ampicillin by the addition of a hydroxyl group, but is better absorbed from the gastro-intestinal tract.

The most important side effect of the penicillins is hypersensitivity which cause rashes and anaphylaxis, which can be fetal. Individuals who have experienced anaphylaxis, urticaria, or rash immediately after penicillin administration are at increased risk of immediate hypersensitivity to penicillin; these individuals should not receive a beta-lactam antibiotic. Patients who are allergic to one penicillin will be allergic to all because the hypersensitivity is related to the basic penicillin structure. Individuals who develop a minor rash or a rash that occurs more than 72 hours after penicillin administration are probably not allergic to penicillin and in these individuals a penicillin should not be withheld unnecessarily on serious infections ; the possibility of an allergic reaction should, however, be borne in mind.

A rare but serious toxic effect of the penicillins is encephalopathy due to cerebral irritation. This may result from excessively high doses or in patients with severe renal failure. The penicillins should not be given by intrathecal injection because they can cause encephalopathy which may be fatal.

Another problem relating to high doses of penicillin, or normal dose given to patients with renal failure, is the accumulation of electrolyte since most injectable penicillins contain either sodium or potassium.

Diarrhea frequently occurs during oral penicillin therapy. It is most common with broad- spectrum penicillins, which can also cause antibiotic associated colitis.

Penicillin G, Sodium crystalline

Injection, 1 million IU, 10 million IU, 20 million IU in vial

Indications: throat infections, pneumonia, otitis media, lyme disease in children; streptococcal endocarditis; meningococcal meningitis; necrotizing enterocolitis, necrotizing fascitis; leptospirosis, neurosyphilis, anthrax; actinomycosis; brain abscess; gas gangrene; cellulitis; osteomyelitis.

Cautions: history of allergy (see notes above); renal failure; heart failure; pregnancy and breastfeeding.

Drug interactions: methotrexate

Side effects: - hypersensitivity reactions including anaphylaxis, serum sickness - like reactions, hemolytic anemia and interstitial nephritis; neutropenia, thrombocytopenia, coagulation disorders and central nervous system toxicity including convulsions reported (especially with high doses or in severe renal impairment), paraesthesia with prolonged use; diarrhea and antibiotic associated colitis; see also notes above.

Contraindications: - penicillin hypersensitivity (see notes above); avoid intrathecal route

Dose and Administration

Mild to moderate infections due to sensitive organisms, by intramuscularly injection or by slow intravenous injection or by intravenous infusion, Adult, 0.6 - 2.4 g daily in 2 - 4 divided doses, with higher doses in severe infections and duration of treatment depending on disease; Neonate, 50 mg/kg daily in 2 divided doses; Infant 1 to 4 weeks, 75 mg/kg daily in 3 divided doses; Child 1 month to 12 years, 100 mg/kg daily in 4 divided doses, with higher doses in severe infections.

Bacterial endocarditic, by slow intravenous injection or by intravenous infusion, Adult up to 7.2g daily in 6 divided doses.

Meningococcal meningitis, by slow intravenous injection or by intravenous infusion, Adult up to 14.4 g daily in divided doses; Premature infant and Neonate 100 mg/kg daily in 2 divided doses; Infant 150 mg/kg daily in 3 divided doses. Child 1 month to 12 years, 180 - 300 mg/kg daily in 4 - 6 divided doses.

Suspected meningococcal disease (before transfer to hospital), by intramuscularly injection or by slow intravenous injection, Adult and child over 10 years, 1.2 g; Child 1 to 9 years, 600 mg; Child less than 1 year, 300 mg.

Neurosyphilis, by slow intravenous injection, Adult 1.8 - 2.4 g every 4 hours for 2 weeks.

Congenital syphilis, by intramuscularly injection or by slow intravenous injection, Child up to 1 years, 30 mg/kg daily in 2 divided doses for 10 days, Child over 2 years, 120 - 180 mg/Kg (to maximum of 1.44g) daily in divided doses for 14 days.

Reconstitution and Administration. According to manufacturer’s directions

Storage: - at room temperature. Prior to reconstitution.

Penicillin G, Benzathine

Injection, 0.6, 1.2, 2.4 million IU in Vial.

Indications: - streptococcal pharyngitis; diphtheria carrier state; syphilis and other treponemal infections (yaws, pinta, bejel); rheumatic fever prophylaxis.

Cautions: - history of allergy (see notes above); renal failure; pregnancy and breast feeding

Drug interactions: - methotrexate

Contra indications: see under penicillin G, sodium crystalline; and neurosyphilis

Side effects: - see under penicillin G, sodium crystalline

Dose and Administrations

Streptococcal pharyngitis; primary prophylaxis of rheumatic fever, by deep intramuscular injection. Adult and Child over 30 kg body-weight, 900 mg as a single dose; Child under 30 kg body - weight, 450 - 675 mg as a single dose.

Secondary prophylaxis of rheumatic fever, by deep intramuscular injection, Adult and Child over 30 kg body-weight, 900 mg once every 3 - 4 weeks; Child under 30 kg body-weight, 450 mg once every 3 - 4 weeks.

Early syphilis, by deep intramuscularly injection, Adult 1.8 g as a single dose, divided between 2 sites.

Late syphilis, by deep intramuscularly injection, Adult 1.8 g divided between two sites, once weekly for 3 consecutive weeks.

Congenital syphilis (where no evidence of CSF involvement), by deep intramuscular injection, child up to 2 years, 37.5 mg/kg as a single dose.

Yaws, Pinta, and bejel, by deep intramuscularly injection, Adult 900 mg as a single dose; child 450 mg as a single dose.

Reconstitution and Administration. According to manufacturer’s directions.

Storage: store between 2 and 8°c.

Phenoxymethyl Penicillin

Tablet, 125 mg, 250 mg, 500,000 IU
Oral suspension, 125 mg/5ml, 50000 IU/ml

Indications: tonsillitis, otitis media, erysipelas; rheumatic fever and pneumococcal infection prophylaxis.

Cautions, Contraindications, Drug interactions, Side effects; see under penicillin G, sodium crystalline

Dose and Administration

Infections due to sensitive organisms, by mouth, Adult 500 - 750 mg every 6 hours; child up to 1 year, 62.5 mg every 6 hours, child 1 - 5 years, 125 mg every 6 hours; child 6 - 12 years, 250 mg every 6 hours.

Secondary prophylaxis of rheumatic fever, by mouth, adult 500 mg twice daily; child 1 - 5 years, 125 mg twice daily; Child 6 - 12 years, 250 mg twice daily.

Note: Phenoxymethyl penicillin should be taken at least 30 minutes before or 2 hours after food.

Storage: -at room temperature in a tight container.

Indications: - for the treatment of respiratory infections (e.g. pneumonia), acute otitis media, skin structure infections, uncomplicated urogenital gonorrhea, and syphilis.

Cautions: -same as penicillin G, benzathine and also caution in the treatment of gonococcal infections during pregnancy and in children.

Drug interactions: - see under penicillin G, sodium crystalline

Side effects: -hypersensitivity reactions such as skin rash, fever, joint pains, edema and anaphylaxis may occur.

Contraindications: -known hypersensitivity to any penicillin and/or procaine.

Dose and Administration: - Intramuscular injection only.

Adults:

Gonorrhea (acute, uncomplicated) - 4,800,000 IU (2,400,000 IU in each buttock). Repeat the same dose next day.

Syphilis- Primary, secondary, or latent (of not more than 2 years duration)- 600,000 IU daily for 8 days. Tertiary (2 year and more)- 600,000 IU daily for 10-15 days.

Note: Remember to treat always the sexual partner.

Pneumonia, acute otitis media, skin or skin structure infections-Adults and children (12 years and over): 600,000-1,200,000 IU daily for 5- 7days.

Maximum dose -100,000 IU of penicillin G/kg of body weight in divided doses.

Children (below 12 years): Treatment is given daily for 5-7 days, 1-5 months (3-5kg) -100,000 IU daily, 6-12 months (6-10kg) -200,000 IU daily, 1- 6 years (11-20kg) -300,000 IU daily, 1-5 years (21-30kg) - 400,000 IU daily.

Storage: - at room temperature. After reconstitution, it should be used with in 14 days provided it is stored between 2-4°c or within 4 days at about 20°c.

Phenoxymethyl penicillin, potassium

Suspension, 195 mg/5ml
Tablet, 390 mg
See under Phenoxymethyl penicillin

Ampicillin

Capsule, 250 mg, 500 mg
Oral suspension, 125 mg/5ml, 250 mg/5ml
Drop, 100 mg/ml
Injection, (sodium), 250 mg, 500 mg, 1 g in vial

Indications: -for treatment of genitourinary tract infection including gonorrhea in female and urethritis in males and females, meningococcal meningitis, acute otitis media, paratyphoid fever, pharyngitis, pneumonia, bacterial septicemia (IV only), sinusitis, and for skin and soft tissue infections including burn wound infections.

Cautions: - caution in patients with history of allergy, renal function impairment, GIT disease especially ulcerative colitis, regional enteritis, or antibiotic associated colitis mononucleosis infections.

Drug interactions: -probenecid (except in cases of gonorrhea and other STD), allopurinol, erythromycin, sulfonamides, tetracyclines and estrogen containing contraceptives.

Side effects: - allergic reaction, specifically anaphylaxis (bronchospasm, sudden or severe decrease in blood pressure), skin rash, joint pain, fever, GIT reaction (mild diarrhoea, nausea, vomiting), oral candidiasis (sore mouth or tongue), pseudomembraneous colitis (severe abdominal or stomach cramps and pain, abdominal tenderness, watery and severe diarrhoea).

Contraindications: - known hypersensitivity (allergy) to any penicillines.

Dose and Administration

By mouth, usual adult dose, 0.25 - 1 g every 6 hours, at least 30 minutes before food; Child under 10 years, half adult dose.
Urinary - tract infections, 500 mg every 8 hours; Child under 10 years, half adult dose

By intramuscular injection or intravenous injection or infusion, 500 mg every 4 - 6 hours; Child under 10 years, half adult dose.

Meningitis (in combination with another antibiotic if necessary), by intravenous infusion, 2 g every 4 hours for 5 days in meningococcal disease or for 10 - 14 days in listerial meningitis.

Storage: - at room temperature.

Amoxicilline

Capsule, 250 mg, 500 mg
Injection, 250 mg, 500 mg in vial
Syrup, 250 mg/5ml

Indications: - see under Ampicillin, and under dose and administration; also endocarditis prophylaxis and treatment, meningococcal disease and adjunct in listerial meningitis; Helicobacter pylori eradication

Cautions, Contraindications and Side effects; see under Ampicillin

Dose and Administrations

Infections due to sensitive organisms, By mouth, Adult and Child over 10 years, 250 mg every 8 hours, doubled in severe infections; Child up to 10 years, 125mg every 8 hours, doubled in severe infections.

Short Course Oral therapy

Dental abscess, 3 g repeated after 8 hours

Urinary - tract infections, 3 g repeated after 10 - 12 hours.

Otitis media, Child 3 - 10 years, 750 mg twice daily for 2 day.

By intramuscularly injection, 500 mg every 8 hours; Child, 50 - 10 mg/kg daily in divided doses

By intravenous injection or infusion, 500 mg every 8 hours increased to 1g every 6 hours; Child, 50 - 100 mg/kg daily in divided doses

Meningitis (in combination with another antibiotic if necessary), by intravenous infusion, 2 g every 4 hours for at least 5 days in meningococcal disease or for 10 - 14 days in listerial meningitis.

Enterococcal endocarditis (in combination with another antibiotic if necessary), by intravenous infusion, 2 g every 4 hours.

Storage: - at room temperature in a tight container.

Cloxacilline sodium

Capsule, 250mg, 500mg
Syrup, 125mg, 250mg in each 5ml
Injection, 250mg, 500mg in vial

Indications: - infections due to beta-lactamase-producing staphylococci including impetigo, cellulitis and other soft-tissue infections; staphylococcal endocarditis, septicaemia, pneumonia and osteomyelitis.

Cautions: - history of allergy, renal function impairment, GIT disease especially ulcerative colitis, regional enteritis, antibiotic associated colitis.

Drug interactions: - probenecid, chloramphenicol, erythromycin, sulfonamide, and tetracyclines.

Side effects: - allergic reaction, specifically prophylaxis (bronchospasm, hypotension), skin rash, joint pain, fever, GIT reaction (mild diarrhoea, nausea, vomiting), oral candidiasis (sore mouth or tongue), pseudomembraneous colitis (sever abdominal or stomach cramp; and pain, abdominal teaderness, watery and severe diarrhoea)

Contraindications: - known hypersensitivity or allergy to penicillines.

Dose and Administration

Usual adult and adolescent dose - Oral, 250 to 500mg (base) every six hours. Maximum dose up to 6gm. IV - 250 to 500mg (base) every six hours maximum - 6gms (base) daily

Usual pediatric dose- Infants and children up to 20kg of body weights - Oral, 6.25 to 12.5mg (base) per kg of body weight every six hours or IV, 6.25 to 12.5mg (base) per kg of body weight every six hours.

Storage: - store at room temperature. The injectable should be stored at room temperature prior to reconstitution.