Syntarpen: composition and presentation
Syntarpen comes as film-coated tablets; each contains 500 mg of cloxacillin as the sodium salt. That is the only strength and the only form at issue when the medicine is taken at home: where the description mentions intramuscular and intravenous administration, it is speaking of other dosage forms and of hospital. The medicine is dispensed on prescription, as all systemic antibiotics are.
The tablet is taken one hour before a meal or two hours after it — and that is not a preference but a condition: food hinders the absorption of cloxacillin, and taking it with a meal simply reduces the dose that reaches the blood. The formulation contains lactose, so the medicine does not suit people with the rare hereditary galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption syndrome.
How Syntarpen works
Cloxacillin is an antibiotic from the group of semisynthetic penicillins of isoxazolyl structure. It acts bactericidally, that is, it kills the microbe rather than holding back its multiplication. The mechanism is set out step by step: the medicine blocks the activity of transpeptidase and thereby prevents bonds forming between the pentapeptides of the glycopeptide of the bacterial wall; the unfinished wall stops holding the cell together, and the activation of cellular hydrolases finishes the job with lysis — the bacterium simply dissolves.
Its principal property, though, lies elsewhere, and it is what the medicine exists for. Staphylococci are able to produce penicillinases, enzymes that destroy ordinary penicillin before it can act. Cloxacillin is resistant to staphylococcal penicillinases, which is why it is used where penicillin is powerless. Synergy is noted as well: with fusidic acid and with ampicillin cloxacillin strengthens the effect of each.
Indications
Cloxacillin is used in infections caused by staphylococci, and the list is a specific one: infections of the skin and soft tissues, furunculosis among them; infections of the lower respiratory tract; purulent complications after burns and after surgery; infections of bone and marrow, mainly post-traumatic. What binds that list together is not an organ but the pathogen — the medicine is chosen not by where it hurts but by what caused the inflammation.
The last entry carries an important proviso: the oral form is given at a later stage of treatment. In other words, osteomyelitis is not started on tablets — the antibiotic is first given parenterally, and the tablets continue what was begun. Another proviso covers every indication at once: before treatment starts, official guidance on the use of antibiotics should be taken into account. For an antistaphylococcal penicillin that is no formality — the medicine has a narrow purpose, and spending it on infections caused by other pathogens is doubly pointless.
Method of use and dosage
The size of the dose depends on several circumstances at once: the severity of the infection, the susceptibility of the organism that caused it, the patient's condition, age and body weight. Adults and children weighing more than 20 kg are usually given 500 mg every 6 hours — one tablet four times a day at equal intervals, the night one included. In very severe infections cloxacillin is recommended intramuscularly or intravenously, and in children weighing up to 20 kg intravenously; tablets do not serve in those cases.
Together with the rule about food this makes for a demanding schedule: four doses a day, each of which must fall either an hour before eating or two hours after. Planning it out in advance is easier than adjusting on the move. In renal impairment the medicine is used with caution: the dose may need reducing or the interval between doses lengthening. The length of treatment is set by the severity and type of infection, and to that is added a rule common to antibiotics and among the most often broken: cloxacillin is taken for a further 2 to 4 days after the symptoms have gone. Stopping as soon as the fever falls and the focus heals is the shortest route to a relapse and to a resistant strain.
Contraindications
The section consists of a single sentence: the medicine is contraindicated in hypersensitivity to cloxacillin, to beta-lactam antibiotics or to any excipient. Short, but wide in its reach — beta-lactams are not only the penicillins but the cephalosporins too, and naming the whole group means that an allergy to any of them closes the door on cloxacillin as well.
The practical consequence is this: before prescribing it the doctor must establish whether there have been hypersensitivity reactions in the past to penicillins, cephalosporins or other medicines. The patient should recall not only the word "allergy" but also exactly how it showed itself: a rash two days after starting and swelling of the lips ten minutes in are reactions of very different danger, and the doctor needs both details.
Special warnings and precautions
Very rarely, treatment with cloxacillin brings on severe features of hypersensitivity, up to an anaphylactic reaction. Its likelihood is higher when the antibiotic is given parenterally and in people prone to allergic reactions to a wide range of substances; such reactions have also been described in people allergic to penicillin. The order of emergency care is stated plainly and strictly: in anaphylactic shock or angioedema, epinephrine is given first, then an antihistamine, and a corticosteroid last of all, with breathing, pulse and blood pressure monitored throughout.
The second field of attention is prolonged use. During it, renal and hepatic function and the peripheral blood count are checked periodically. Prolonged use can also cause overgrowth of organisms not susceptible to the antibiotic: where signs point, for instance, to a fungal infection, the medicine is stopped and appropriate treatment prescribed. Severe, persistent diarrhoea is dealt with separately: the possibility of pseudomembranous colitis, caused in most cases by Clostridium difficile, is then considered. Cloxacillin is stopped and proper treatment begun, while agents that slow peristalsis are contraindicated — by holding back the bowel contents they would hold back the toxin as well. There are no data on the effect on the ability to drive, but concentration may be impaired by the adverse effects themselves: headache, dizziness, drowsiness, a state of disorientation.
Interactions with other medicines
The interactions of cloxacillin are described with unusual precision — not only what is strengthened or weakened, but which antibiotics it works with in combination and which it does not.
| Medicine or situation | What happens |
| Probenecid | raises the serum concentration of cloxacillin and lengthens its half-life |
| Oral anticoagulants | cloxacillin strengthens their effect and with it the risk of bleeding |
| Methotrexate | its elimination by the renal tubules slows, so the toxicity of methotrexate rises |
| Cephalosporins | patients allergic to them may prove sensitive to cloxacillin as well — cross-allergy |
| Hormonal contraceptives with oestrogens | their effectiveness may fall; while the antibiotic is being taken, an additional non-hormonal method of contraception is advised |
| Ampicillin and fusidic acid | synergy — the joint effect is stronger than the sum of the separate ones |
| Erythromycin, tetracyclines, chloramphenicol | antagonism — these antibiotics weaken the action of cloxacillin |
| Laboratory tests | the determination of 17-oxosteroids and oxogenic steroids in urine is distorted, and testing urine for glucose by reduction methods may give a false positive |
Two rows of that table are worth remembering above the rest. The one on contraception, because it is seldom thought of, and a short course of an antibiotic is enough for the protection to weaken. And the one on antagonism: "add another antibiotic to be sure" is, in combination with erythromycin, tetracyclines or chloramphenicol, a decision that is not merely useless but makes the outcome worse.
Pregnancy and breastfeeding
Sufficiently large, well-controlled studies in pregnant women have not been carried out, and the results of reproduction studies in animals do not always fully reflect a medicine's effect on the human foetus. From those two premises follows the conclusion of the description: cloxacillin may be given to pregnant women only where there is clear necessity. The decision rests with the doctor, weighing the severity of the infection itself — an untreated staphylococcal infection in pregnancy is not harmless either.
The medicine is excreted into breast milk, so it is given to nursing women with caution: adverse effects in the child are possible — allergy, diarrhoea and yeast infection. There is no outright ban, but once treatment has begun the child's condition is watched more closely than usual and any change reported to the doctor.
Adverse reactions
Every reaction listed in the description is placed in the "very rare" category, and that is worth holding in mind while reading a long list. The most serious are those of the immune system. Immediate allergic reactions include hives, itching, angioedema, spasm of the larynx and the bronchi, a fall in blood pressure, vascular collapse and even death. Delayed ones develop from 48 hours to two or four weeks after treatment begins and look different: fever, malaise, hives, pain in the muscles, joints and abdomen, skin rashes; serum sickness and allergic vasculitis have also been described. On any of these reactions the medicine is withdrawn at once.
In the blood, transient eosinophilia, leukopenia, neutropenia, disturbed platelet function, thrombocytopenia, agranulocytosis, bone marrow suppression and haemolytic anaemia have been recorded. In the nervous system, signs of neurotoxicity are described — transient overactivity, agitation, restlessness, drowsiness, disorientation and dizziness — and they arise chiefly in patients with renal impairment receiving large doses. The digestive tract answers with nausea, vomiting, diarrhoea, inflammation of the oral mucosa, black hairy tongue and pseudomembranous colitis; the liver with raised aminotransferase activity and, in isolated cases, cholestatic jaundice and hepatitis, which pass once the medicine is stopped. Skin reactions run from rash, itching and hives to erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis and bullous exfoliative dermatitis. In the kidneys, absence of urine, interstitial nephritis and disturbed tubular function are described; they show themselves most often as rash, fever, eosinophilia, blood and protein in the urine, occur in patients on high doses or with existing kidney disease, and resolve once the medicine is withdrawn.
Overdose
The overdose section takes up one sentence in the description: the medicine is withdrawn at once and symptomatic treatment given. There is no specific antidote, and that is not a gap but a consequence of the substance's profile — with penicillins an overdose rarely produces a clinical picture of its own beyond an intensification of the usual adverse effects.
One scenario from the warnings section has real practical weight: signs of neurotoxicity — agitation, restlessness, confusion, dizziness — occur in patients with renal impairment receiving large doses. That is precisely the situation in which an excess of the medicine in the body shows itself plainly, and it comes not from one tablet too many but from a dose left unadjusted when the kidneys are working poorly.
How to get a Syntarpen prescription online
Syntarpen is dispensed on prescription, and at e-zdrowie.com it can be arranged remotely. You fill in a medical questionnaire, the doctor reviews the answers and, if the medicine is suitable, issues an electronic prescription: the code arrives by message, and any Polish pharmacy will dispense the tablets against it. The limits of the format matter here: an antibiotic is chosen by the pathogen, and cloxacillin is meant for staphylococcal infections, so the questionnaire must give the doctor grounds to believe that is what this is.
Describe where the focus is and what it looks like, when it all began, whether there is a fever, whether a culture with susceptibility testing was done and what it showed. State whether the medicine has been prescribed before, at what dose and for how long, and whether a course of intravenous antibiotic came first — in bone infections the tablets continue treatment already begun rather than replacing it. Be sure to report allergy to penicillins and cephalosporins and how it showed itself, kidney and liver disease, pregnancy or breastfeeding, and the use of anticoagulants, methotrexate and hormonal contraceptives. Rapidly spreading redness, mounting pain, a high fever or a purulent focus that needs incision are grounds for examination in person, not for a remote prescription.
