Phenoxymethyl Penicillin [Penicillin V]

For the treatment of mild to moderately severe bacterial infections, if these are due to penicillin susceptible pathogens and respond to therapy with oral penicillin, such as:

• infections of the ear, nose and throat regions, e.g., tonsillitis, pharyngitis, laryngitis, otitis media, sinusitis.
• infections of the lower respiratory tract, e.g., bronchitis and pneumonia, bronchopneumonia.
• infections due to beta-hemolytic streptococci of group A, e.g., scarlet fever, erysipelas, rheumatic fever.
• skin infections, e.g., pyodermia, furunculosis, phlegmon, erysipeloid, erythema migrans, insofar as the micro-organisms are penicillin-susceptible.
• lymphadenitis and lymphangitis of bacterial origin.
• infections of the buccal cavity, gums or jaws, e.g., inflammatory infiltrates, delayed dentition stages II and III, antral fistulae, secondary bacterial infection with Gram-positive pathogens following virus-induced gingivitis or stomatitis.

For prophylaxis of scarlet fever; also to prevent recurrences of rheumatic fever. For prophylaxis of infection after dental and oral surgical procedures or dental extractions in certain high risk patients (e.g. with congenital cardiac defects, artificial heart valves, rheumatic endocarditis). In some cases, combination with another appropriate antibiotic may be indicated.

Phenoxymethyl penicillin or penicillin V is acid-stable and is absorbed from the upper part of the small intestine. Of different forms of Phenoxymethyl penicillin, the potassium salt of Phenoxymethyl penicillin is best absorbed. This may be given with meals but maximum absorption is achieved when drug is administered orally at least 1 hour before or 2 hours after the meal. Phenoxymethyl penicillin offers a very convenient means of treating Grampositive infections. Phenoxymethyl penicillin has the distinct advantage over penicillin G in resistance to inactivation by gastric acid.

The dosage of Phenoxymethyl penicillin should be determined according to the sensitivity of the causative micro-organism and the severity of the infection, and adjusted to the clinical response of the patient.

Adults: 250-500 mg 6 hourly

Children (above 1 year):

• 125-250 mg 6 hourly
• 125 mg/5 ml powder for suspension: 1-2 teaspoonful (5-10 ml) 6 hourly
• 250 mg/5 ml powder for suspension: ½-1 teaspoonful (2.5-5 ml) 6 hourly

Infants (below 1 year):

• 62.5-125 mg 6 hourly.
• 125 mg/5 ml powder for suspension: ½-1 teaspoonful (2.5-5 ml) 6 hourly, or as prescribed by the physician.

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

Administration

Phenoxymethyl Penicillin is best taken on an empty stomach, preferably one hour before meals. The tablets are swallowed without chewing with sufficient amounts of liquid. Before each use of this syrup, the bottle has to be shaken vigorously.

Food: Concurrent intake of food leads to a reduction in the rate of absorption. Therefore, Phenoxymethyl penicillin is best taken on an empty stomach, preferably one hour before meals, in order to reach the highest possible rate of absorption.

Drug interactions: Concomitant administration of penicillins may lead to increased levels of methotrexate in serum and potentiate its toxic effects. Monitoring of methotrexate serum levels is therefore necessary.

If diarrhoea occurs as a consequence of treatment with Phenoxymethyl penicillin, the absorption of other orally administered drugs may be disturbed and their effcacy may consequently be impaired. If penicillins are combined with bacteriostatic chemotherapeutics or antibiotics (e.g., tetracyclines, chloramphenicol), the activity of penicillins may be attenuated or abolished. Concurrent administration of probenecid inhibits the renal excretion of penicillins. Concurrent use of indomethacin, phenylbutazone, salicylates or sulfinpyrazone may cause elevated and prolonged serum levels of phenoxymethylpenicillin.

Administration of penicillins may cause a transient reduction in plasma concentrations of oestrogens and gestagens. The effectiveness of oral contraceptives is therefore uncertain.

The absorption of Phenoxymethyl penicillin may be reduced where intestinal sterilization with aminoglycosides (e.g. neomycin) has just been performed or is still in progress. Combined use of penicillins and oral anticoagulants (e.g. warfarin) may prolong prothrombin time/INR.

Interference with laboratory and diagnostic tests: Non-enzymatic urine glucose determinations and tests for urobilinogen may give false-positive results.

Phenoxymethyl Penicillin must not be administered in patients with hypersensitivity to penicillins or any of the excipients of this. Phenoxymethyl Penicillin must not be used to treat patients with severe gastrointestinal disorders accompanied by vomiting and diarrhea.

Occasionally, hypersensitivity reactions involving the skin (e.g. urticaria, morbilliform or scarlatiniform rashes, pruritus), eosinophilia or more serious allergic reactions, e.g. drug fever, vasculitis, serum sickness or interstitial nephritis, may develop. Anaphylactic or anaphylactoid reactions accompanied by, e.g- angioneurotic oedema, oedema of the larynx, bronchial spasm and shock may occur.

In the event of signs pointing to anaphylactic/anaphylactoid reactions, the treatment must be terminated immediately. In occasional instances, there may be skin rashes or inflammation of mucous membranes, especially in the region of the mouth (stomatitis); dryness of the mouth and disorders of taste may rarely occur.

The occurrence of severe bullous skin reactions- usually involving the mucosae- has been reported in isolated cases (Stevens-Johnson syndrome, Lyell's syndrome). Gastrointestinal disturbances with, e.g., nausea, vomiting, abdominal pain, loose stools, or diarrhoea may develop.

Diarrhoea may sometimes be a symptom of enterocolitis which may, in some cases, be haemorrhagic. A particular form of enterocolitis that can occur with antibiotics is pseudomembranous colitis (in most cases due to Clostridium diffcile). This must be considered in patients in whom severe, persistent diarrhoea occurs during treatment or in the initial weeks thereafter. Even if pseudomembranous colitis is only suspected, administration of Phenoxymethyl penicillin must be halted immediately. This type of colitis requires immediate and appropriate treatment by a physician. Drugs that inhibit intestinal peristalsis must not be taken in such cases. In isolated cases, particularly after high doses and prolonged administration, changes in blood picture such as reduction in the number of white blood cells (e.g.,leucopenia, granulocytopenia, agranulocytosis), erythrocytes (e.g., due to haemolytic anaemia), thrombocytes, or pancytopenia and myelosuppression may occur. During treatment for spirochaetal infections, Herxheimer's reaction characterized by the occurrence or worsening of general symptoms such as fever, chills, headache, and joint pains may develop. In isolated cases, drug-induced aseptic meningitis may occur.

In extremely rare cases, transient discolouration of the teeth may be seen during treatment with Phenoxymethyl penicillin. Administration of antibiotics, especially if prolonged, may lead to the proliferation of resistant micro organisms.

Beta-lactams predispose the patient to encephalopathy risk (which may include convulsions, confusion, impairment of consciousness, movement disorders), particularly in case of overdose or renal impairment.

Phenoxymethylpenicillin crosses the placenta. Given the appropriate indication, this may be used at any time throughout pregnancy. Phenoxymethylpenicillin passes into the breast milk in small amounts. This may be used during lactation; however, diarrhoea and yeast colonization of mucous membranes may occur in the infant.

The possibility of cross-allergy between cephalosporins and penicillins must be considered. When treating patients with heart diseases or serious electrolyte disturbances of other origin, the potassium content of Phenoxymethyl Penicillin may have to be considered. Beta-lactams predispose the patient to encephalopathy risk (which may include convulsions, confusion, impairment of consciousness, movement disorders), particularly in case of overdose or renal impairment.

Administration of antibiotics, especially if prolonged, may lead to the proliferation of resistant micro-organisms. The patient's condition must therefore be checked at regular intervals. If a secondary infection occurs, appropriate measures must be taken. In patients with diabetes mellitus, the sugar content of Phenoxymethyl Penicillin syrup must be taken into consideration.

There is no indication of impaired ability to drive, or to operate machinery. Beta-lactams predispose the patient to encephalopathy risk. In the case of adverse reactions such as encephalopathy (which may include convulsions, confusion, impairment of consciousness, movement disorders), the patient should not operate machines or drive a vehicle.

The toxicity of phenoxymethylpenicillin is low, and it has a broad therapeutic range. When a multiple therapeutic dose is taken orally once only, phenoxymethylpenicillin has no acute toxicity. There is a risk of encephalopathy in cases of administration of beta-lactam antibiotics, particularly in case of overdose or renal impairment. Special measures in the event of overdosage, other than discontinuation of the medication, are not required. Elimination of phenoxymethylpenicillin can be accomplished through haemodialysis.

Benzylpenicillin & Phenoxymethyl penicillin.

Store in a cool and dry place, protect from light.