Vigamox: composition and presentation
Vigamox is an eye drop solution. One millilitre contains 5.45 mg of moxifloxacin hydrochloride, equivalent to 5 mg of moxifloxacin. The description also gives a more vivid figure: a single drop carries 190 µg of the active substance. The whole of the treatment amounts to that dose, and grasping how little antibiotic reaches the body when it is instilled into the eye explains a good half of the safety sections.
The route of administration is stated firmly: for use in the eye only. The solution is not intended for injection, must not be given subconjunctivally and must not be introduced directly into the anterior chamber of the eye. The caveat looks superfluous for home use, but it is addressed to medical staff as well: a clear sterile solution in a dropper bottle is easily mistaken for a preparation meant for intraocular use, and the consequences of such a mistake are serious.
How Vigamox works
Moxifloxacin is a fourth-generation fluoroquinolone. It inhibits two bacterial enzymes, DNA gyrase and topoisomerase IV, without which the replication, repair and recombination of bacterial DNA are impossible. The microbe does not merely stop dividing: it loses the ability to assemble and mend its own chromosome, and that is what sets fluoroquinolones apart from antibiotics that break down the cell wall.
Resistance to fluoroquinolones, moxifloxacin included, usually develops through chromosomal mutations in the genes coding for those same DNA gyrase and topoisomerase IV. In Gram-negative bacteria it may also depend on mutations in the mar gene system, which governs multiple antibiotic resistance, and in the qnr genes linked to quinolone resistance. The practical conclusion is this: cross-resistance with beta-lactams, macrolides and aminoglycosides is not to be expected, because those groups act by a different mechanism. Put differently, a failure of penicillin treatment does not predict a failure of moxifloxacin, nor the other way round.
Indications
The indication is set out in a single sentence: topical treatment of purulent bacterial conjunctivitis caused by strains susceptible to moxifloxacin. Every word in it does work. Bacterial — meaning viral and allergic conjunctivitis fall outside the indications, and those two account for most cases of a red eye. Purulent — this is about discharge that glues the lashes together in the morning, not simply redness and watering. Susceptible — if the pathogen is resistant to moxifloxacin, the drops will not work however diligently they are instilled.
To this is added a requirement usually reserved for systemic antibiotics: prescribing should take account of official guidance on the proper use of antibacterial agents. For an eye drop that reminder is no formality. An antibiotic spent on viral conjunctivitis not only fails to help the individual patient but takes part in selecting resistant strains, and a fourth-generation fluoroquinolone is a reserve not worth squandering.
Method of use and dosage
Adults, including patients aged 65 and over, instil one drop into the affected eye or into both eyes three times a day. Improvement usually comes within five days, but treatment is continued for a further two to three days after it — the habit of dropping the drops as soon as the eye clears leaves some of the bacteria alive. If there is no improvement within five days of starting, the correctness of the diagnosis and of the chosen treatment is reconsidered. The overall duration depends on the severity of the disease and on the clinical and bacteriological course of the infection. In children and adolescents the dose is not adjusted, nor is it in hepatic or renal impairment.
Several rules for handling the bottle affect the outcome as much as the schedule does. The dropper tip must not touch the eyelids, the areas next to the eye or any other surface, since both the tip and the solution itself become contaminated. To keep the drops from being absorbed through the lining of the nose, the nasolacrimal duct is closed for two to three minutes immediately after instillation by pressing it with the fingers; this matters especially in newborns and children. If the protective collar is loose after the cap is removed, it is taken off before the medicine is used. When more than one topical eye preparation has been prescribed, a gap of at least five minutes is left between them, and eye ointments are applied last.
Contraindications
The only outright contraindication is hypersensitivity to moxifloxacin or to any of the excipients of the drops. There are no further bans in this section, and against the background of extensive warnings such brevity comes as a surprise.
The route of administration explains it. Systemic moxifloxacin carries a long list of restrictions, but after instillation into the eye its plasma concentration is incomparably lower than after therapeutic oral doses, so most systemic prohibitions do not carry over to the drops. Yet "lower" does not mean "none": class-specific reactions are described here too, and that is why the main restrictions were placed in the warnings section. The same section gathers the situations in which the conjunctivitis is caused by a pathogen these drops should not be used against — a microbiological restriction rather than an allergic one.
Special warnings and precautions
The chief warning is carried over from experience with quinolones given by mouth and by vein. In such patients serious and sometimes fatal hypersensitivity reactions, anaphylactic ones among them, have been described, and some arose after the very first dose. They ran with cardiovascular collapse, loss of consciousness, angioedema involving the larynx, throat or face, obstruction of the airways, breathlessness, hives and itching. If an allergic reaction occurs, the medicine is withdrawn; a severe acute reaction to moxifloxacin or to any component of the drops may call for immediate emergency treatment and, where clinically warranted, oxygen and measures to secure normal breathing. The second class-specific risk is inflammation and rupture of tendons, including the Achilles tendon and those of the shoulder and hand; cases have been described that required surgery or led to lasting disability, and the likelihood is higher in older people and in those receiving corticosteroids at the same time. After instillation into the eye the plasma concentration of moxifloxacin is far lower than after oral use, but the caution stands: at the first signs of tendon inflammation, treatment with the drops is stopped.
| Situation | Why the drops are not enough |
| Conjunctivitis in the newborn | data on efficacy and safety are very limited, so use is not recommended |
| Gonococcal conjunctivitis, including gonorrhoeal conjunctivitis of the newborn | strains of Neisseria gonorrhoeae resistant to fluoroquinolones occur; the medicine suits neither prophylaxis nor empirical treatment, and systemic therapy is needed |
| Chlamydial infection in children under 2 | the medicine has not been studied in this age group and use is not recommended |
| Chlamydial infection in patients over 2 | appropriate systemic treatment is required |
| Prolonged use | overgrowth of non-susceptible organisms, fungi included, is possible; if superinfection occurs the medicine is stopped and other treatment chosen |
| Wearing contact lenses | lenses must not be used while signs and symptoms of bacterial eye infection are present |
Driving is dealt with separately. The medicine itself has no or negligible influence on the ability to drive and operate machinery but, like any eye drops, it may cause transient blurred vision or other visual disturbance. If vision blurs after instillation, one returns to the wheel or to the machine only once visual acuity has come back.
Interactions with other medicines
No specific interaction studies with this preparation have been carried out. Formally that is a gap, but not an accidental one: concentrations of moxifloxacin in the body after topical administration are so low that interaction with other medicines seems unlikely.
A practical consequence follows: there is no need to change how you take blood-pressure tablets, diabetes medicines or contraceptives because of the drops. What calls for attention is not the systemic side but the local one — the order of instillation when several eye preparations are in use, and the rule about five-minute gaps with ointments last. And one more general point: if moxifloxacin or another fluoroquinolone has also been prescribed by mouth, the total load on the body is set by the tablets, and the warnings about tendons apply first and foremost to them.
Pregnancy and breastfeeding
The pregnancy section is unusual for this medicine in that it ends with permission rather than a ban. Sufficient data on use in pregnant women are lacking, yet no unfavourable effect on the course of pregnancy is to be expected, given the negligible systemic exposure to moxifloxacin when it is instilled into the eye. The conclusion of the description is direct: the medicine may be used during pregnancy. For a fluoroquinolone, which is not usually given to pregnant women by mouth, that is a significant difference, and it arises solely from the route of administration.
The picture with breastfeeding is the same. Whether moxifloxacin passes into human breast milk is unknown; animal studies showed it being excreted in milk at low concentrations after oral administration. At therapeutic doses of the drops, however, no effect on a breastfed child is to be expected, and the medicine may be used while breastfeeding. Interrupting feeding because of a course of eye drops is therefore unnecessary.
Adverse reactions
Safety was assessed in 2252 patients, with the medicine given up to eight times a day and more than 1900 people receiving it on the standard three-times-daily schedule; the group comprised 1389 patients from the United States and Canada, 586 from Japan and 277 from India. No serious ocular or systemic adverse reaction related to the medicine was described in those trials. The most frequently reported effects were eye irritation and eye pain, with an overall frequency of 1 to 2%; in 96% of the patients who had them the reactions were mild, and only one person stopped treatment because of them. In patients under 18 those same two effects proved the commonest, at a frequency of 0.9%, and the nature and severity of reactions in children, newborns included, were the same as in adults.
Among ocular reactions, pain and irritation were recorded often; uncommonly punctate keratitis, dry eye, conjunctival haemorrhage, eye redness, itching, eyelid swelling and a feeling of discomfort; rarely abnormalities of the epithelium and disorders of the cornea, conjunctivitis, blepharitis, swelling of the eye and conjunctiva, blurred or reduced vision, eye strain and reddening of the eyelids. With unknown frequency, internal inflammation of the eye, ulcerative keratitis, corneal erosions and abrasions, raised intraocular pressure, corneal opacity, infiltrates and deposits, eye allergy, keratitis and corneal oedema, photophobia, increased tearing, eye discharge and a foreign-body sensation were reported. Outside the eye, headache and taste disturbance occurred uncommonly, and rarely paraesthesia, vomiting, nasal discomfort, throat and larynx pain, a foreign-body sensation in the throat, a fall in haemoglobin and rises in alanine aminotransferase and gamma-glutamyltransferase; with unknown frequency, dizziness, palpitations, breathlessness, nausea, erythema, rash, itching, hives and hypersensitivity reactions.
Overdose
Not a single case of overdose with this medicine has been described, and this is one of those rare sections where the absence of data comes not from limited experience but from anatomy. The capacity of the conjunctival sac is limited: surplus fluid simply spills over the edge of the eyelid, so instilling more than the eye can hold is practically impossible.
The second scenario is accidental swallowing of the contents of the bottle, say by a child who has reached the medicine cabinet. The total amount of moxifloxacin in one pack is too small to cause adverse effects if swallowed. That is no reason to leave the drops in plain sight, but it is no reason for panic either: special measures are usually unnecessary, and it is enough to contact a doctor and describe the circumstances.
How to get a Vigamox prescription online
Vigamox is dispensed on prescription, and at e-zdrowie.com the prescription can be obtained 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 drops against it. For acute purulent conjunctivitis the format is convenient: the illness starts abruptly, and a trip to the clinic with an inflamed eye is unpleasant in itself.
So that the doctor can decide, describe in the questionnaire what the discharge is like and when it appeared, whether one eye or both turned red, and whether there is pain, photophobia or loss of vision. Be sure to state whether you wear contact lenses, whether you have had eye injuries or operations, whether you are allergic to quinolone antibiotics, whether you are pregnant or breastfeeding, and whether you take corticosteroids. Loss of vision, severe pain, a recent eye injury and symptoms in a newborn are grounds not for a remote prescription but for an examination in person, and in such cases the doctor will refer you to an ophthalmologist.
