Phenopen

Uses

Phenoxymethyl Penicillin is used for the treatment of mild to moderate revere infections caused by susceptible organisms which are mostly Gram-positive. The following infections usually respond to adequate dosage of Phenoxymethyl Penicillin.

Streptococcal infections (without bacteremia): mild to moderately sever infections of upper respiratory tract scarlet fever, mid erysipelas. Bacterial endocarditis due to L-Haemolytic streptococci (combined with streptomycin), lobar pneumonia, infections due to non-penicillinase producing staphylococci Pneumococci infections Acute otitis medie, Meningococci infections Fusospirochetosis vincent's gingivitis and pharyngitis.

Prophylaxis: Prevention of recurrence following rheumatic fever and chorea. Puerperal sepsis, Diphtheria, Anthrax Gonococcal infections, Syphilis and yaws, Actinomycosis.

Phenopen is also used to associated treatment for these conditions: Actinomycosis, Animal bite, Anthrax, Bacterial Endocarditis, Bacterial Infections, Community Acquired Pneumonia (CAP), Erythema Chronicum Migrans, Gingivitis, Necrotizing Ulcerative, Lower Respiratory Tract Infection (LRTI), Scarlet Fever, Skin and Subcutaneous Tissue Bacterial Infections, Streptococcal Pharyngitis, Streptococcal tonsillitis, Mild Otitis media, Mild bacterial upper respiratory tract infections, Moderate Otitis media, Moderate bacterial upper respiratory tract infections, Prophylaxis of Rheumatic fever

How Phenopen works

Phenopen inhibits the biosynthesis of cell wall mucopeptide by binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, which are critical in the cell wall synthesis and maintenance, as well as cell division. This disrupts the third and last stage of bacterial cell wall synthesis. This subsequently leads to cell lysis.

Dosage

Phenopen dosage

The dosge of Phenoxymethyl Penicillinshould be determded accoedgto the snsitivityof the raustive mnro-orgnism and tie severity of tie infection, and adjusted to the clinical respons of the patient

Adults: 250-500 mg 6 hourly

Children: 125-250 mg 6 hourly

• 125 mg/5 ml Syrup: 1 to 2 teaspoonful (5-10 ml) 6 homiy
• 250 mg/5 ml Syrup: ½ to 1 teaspoonful (2.5-5 ml) 6 hourly

Infants: 62.5 -125 mg 6 hourly

• 125 mg/5 ml Syrup: ½ to 1 tea spoonful (2.5-5 ml) 6 hourly, or as prescribed by the physician.

Phenoxymethyl Penicillin is best taken with a empty stomach, preferably at least 1 hour before or 2 hour after meal.

Should be taken on an empty stomach. Take 1 hr before or 2 hr after meals.

Reconstitutions

Powder for oral solution: Add the amount of water specified on the bottle to provide a solution containing 125 mg or 250 mg per 5 ml. The water should be added to the powder in 2 portions and the solution agitated vigorously immediately after each addition.

Side Effects

Common encountered untoward effects include nausea, vomiting, epigastric distress& diarrhoea. The hypersensitivity reactions reported are skin eruptions urticara ad other serum sickness reactions, laryngeal oedema and aaphylaxis.

Toxicity

The oral LD₅₀ is >1040 mg/kg in rats. Nausea, vomiting, black hairy tongue, and epigastric distress are common reactions to oral penicillins. In rare cases, neuromuscular sensitivity and seizures may be seen with antibiotics and supportive treatments are advised and further drug absorption should be limited through induced emesis or gastric lavage, followed by administration of activated charcoal. Severe hypersensitivity reactions, often leading to death, have been reported with penicillin therapies. Although phenoxymethylpenicillin was shown to be excreted in human breast milk, the use of this drug in pregnant or nursing women is regarded generally safe.

Precaution

Patient with history of asthma, seizure disorders, history of β-lactam allergy. Severe renal impairment. Pregnancy and lactation.

Interaction

Reduced absorption with neomycin. May interfere with anticoagulant control. Antagonism of bactericidal effect by chloramphenicol, erythromycin and tetracyclines. May increase toxicity of methotrexate. May reduce the efficacy of OC. Reduced excretion with probenecid and sulfinpyrazone. May inactivate oral typhoid vaccine if ingested concomitantly.

Food Interaction

• Take on an empty stomach. Absorption is increased 1 hour before or 2 hours after food.

Volume of Distribution

Following intravenous administration, the volume of distribution at steady state was 35.4 L. Small amounts of the drug can be found in various tissues, with the highest amount found in the kidneys, with lesser amounts in the liver, skin, and intes­ tines. Phenopen was found in the cerebrospinal fluid. Phenopen was detectable in the placenta and human breast milk.

Elimination Route

Upon oral administration, phenoxymethylpenicillin is rapidly but incompletely absorbed. The bioavailability of phenoxymethylpenicillin ranges from 25 to 60%. Compared to the free acid form of the drug, the calcium or potassium salts of phenoxymethylpenicillin displays better absorption profiles. It is reported that fasting state enhances the drug absorption. The peak plasma concentrations of 200 to 700 ng/mL are achieved in 2 hours following an oral dose of 125 mg. Following an oral dose of 500 mg, the peak plasma concentrations of 3 to 5 μg/mL are reached in 30 to 60 minutes post-dose.

Half Life

Upon oral administration, the half-life is about 30 minutes. It can last up to 4 hours in patients with renal impairment.

Elimination Route

While the drug is rapidly excreted, only 25% of the total dose is detected in the urine. Renal excretion may be delayed in neonates, young infants, and patients with renal impairment.

Pregnancy & Breastfeeding use

There are no contraidications to the ues of penicmin in pregnancy. Phenoxymethyl pencillin is excreted in the breast milk, which might cause allergic reaction to the infants.

Contraindication

It is contraindicated in patients known to be hypersensitive to penicillin. It is also contraindicated in severe acute infections.

Acute Overdose

Symptoms: Nausea, vomiting, stomach pain, diarrhoea, and rarely, major motor seizures. If other symptoms are present, consider the possibility of an allergic reaction. Hyperkalaemia may result, particularly for patients with renal insufficiency.

Management: Symptomatic and supportive treatment. May admin activated charcoal with a cathartic, e.g. sorbitol to hasten drug elimination. May be removed by haemodialysis.

Storage Condition

Tablet or Powder for Oral Solution: Store between 20-25°C.

Reconstituted oral Solution: Store between 2-8°C. Protect from light.

Innovators Monograph

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