New Zealand - English - Medsafe (Medicines Safety Authority)
DateofPreparation:09 th May2007
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New Zealand Data Sheet
QUALITATIVE AND QUANTITATIVE COMPOSITION
Each Doxy-50 tablet contains doxycycline hydrochloride 57 mg (as hyclate, equivalent to
doxycycline 50 mg)
Each Doxy-100 tablet contains doxycycline hydrochloride 114 mg (as hyclate, equivalent to
doxycycline 100 mg)
Excipient(s) with known effect
For the full list of excipients, see section 6.1.
Doxy-50 and Doxy-100 tablets are white, film coated, circular biconvex tablet.
Doxy-50 tablets have a diameter of approximately 6.3 mm.
Doxy-100 tablets are scored on one side and have a diameter of 8 mm.
Doxycycline is indicated in the treatment of uncomplicated chest, urethral, endocervical or rectal
infections in adults caused by susceptible organisms (see below) as shown by culture and
sensitivity testing. It may also be a useful adjunct to amoebicides in acute intestinal amoebiasis
and has a place as adjunctive therapy in severe acne. Doxycycline is active against the following
Rickettsiae: rocky mountain spotted
Fever, typhus fever and the typhus group, Q fever, rickettsial pox, and tick fevers
Agents of lymphogranuloma venereum and granuloma inguinale
The spirochetal agent of relapsing fever (Borrelia recurrentis)
Haemophilis ducreyi (chancroid)
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Pasteurella pestis, and Pasteurella tularensis, Bartonella bacilliformis, Bacteroids species,
Vibriocomma and Vibrio fetus and Brucella species (in conjunction with an
Doxycycline may be active against the following organisms although this should be confirmed by
culture and sensitivity testing since many strains are resistant.
Mima species and Herellea species
Staphylococcus aureus in respiratory, skin or soft tissue infection.
When penicillin is contraindicated, doxycycline is an alternative medicine in the treatment of
infections due to:
Treponema pallidum and Treponema pertenue (syphilus and yaws)
Fusobacterium fusiforme (Vincent's infection)
Dose and method of administration
The usual dose in adults is 200 mg on the first day of treatment followed by a maintenance dose
of 100 mg/day. This may be given as either a single dose or divided doses administered every 12
In the management of more severe infections 200 mg daily should be given throughout the
treatment period. Therapy should be continued at least 24-48 hours after symptoms and fever
have subsided. If used in streptococcal infections, therapy should be continued for 10 days to
prevent the development of rheumatic fever or glomerulonephritis.
For the treatment of acne vulgaris the recommended dose is 50 mg of doxycycline taken daily
with food, for up to 12 weeks.
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In the treatment of acute gonococcal anterior urethritis in males, administer either: 200 mg stat
and 100 mg at bedtime on the first day followed by 100 mg twice daily for 3-7 days, or 300 mg
stat followed by 300 mg one hour later. For acute gonococcal infections in females use 200 mg
When treating uncomplicated urethral, endocervical or rectal infection in adults caused by
chlamydia trachomatis, give 100 mg twice daily for at least 7 days. The treatment of primary or
secondary syphilis requires 300 mg daily in divided doses for at least 10 days.
For children over 12 years of age, the recommended dosage schedule for those under 50 kg is 4
mg/kg on the first day and 2 mg/kg daily subsequently. For children over 50 kg the usual adult
dose is used.
Method of Administration
In all cases Doxy should be administered with adequate amounts of fluid or food and the patient
should remain sitting or standing for up to 2 hours afterwards to prevent the possible
development of oesophageal irritation.
Hypersensitivity to doxycycline, or any other ingredient in Doxy tablets.
Children under 12 years of age. The use of drugs of the tetracycline class, including
doxycycline, during tooth development may cause permanent discolouration of the
teeth (yellow-grey-brown). This adverse reaction is more common during long term use
of the medication but has been observed following repeated short-term courses. Enamel
hypoplasia has also been reported.
Pregnancy. Tetracyclines given during pregnancy affect teeth and skeletal development
(refer to section 4.6 and 5.3).
Nursing mothers. Tetracyclines are excreted into milk and affect teeth and skeletal
development (refer to section 4.6 and 5.3).
Special warnings and precautions for use
Clostridium difficile associated diarrhoea (CDAD) and antibiotic associated
Clostridium difficile associated diarrhoea (CDAD) and antibiotic associated pseudomembranous
colitis have been reported with nearly all antibacterial agents including doxycycline and may
range in severity from mild diarrhoea to fatal colitis. Treatment with antibacterial agents alters
the normal flora of the colon leading to overgrowth of C. difficile and C. difficile produces toxins
A and B which contribute to the development of CDAD. Hypertoxin producing strains of C.
difficile cause increased morbidity and mortality, as these infections can be refractory to
antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who
present with diarrhoea following antibiotic use. Careful medical history is necessary since CDAD
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has been reported to occur over two months after the administration of antibacterial agents.
Mild cases usually respond to drug discontinuation alone. However, in moderate to severe cases
appropriate therapy with a suitable oral antibacterial agent effective against Clostridium difficile
should be considered. Fluids, electrolytes and protein replacement should be provided when
indicated. Drugs which delay peristalsis, e.g. opiates and diphenoxylate with atropine may
prolong and/or worsen the condition and should not be used.
Rarely, oesophagitis and oesophageal ulceration have been reported in patients receiving
doxycycline tablets. Most of these patients took medication immediately before going to bed.
Administration of adequate amounts of fluid with the tablets is recommended to reduce the risk
of oesophageal irritation and ulceration, and late evening ingestion of the dose should be
To reduce the possibility of gastric irritation, it is recommended that doxycycline be given with
food or milk. The absorption of doxycycline is not markedly influenced by simultaneous ingestion
of food or milk.
In venereal disease when coexistent syphilis is suspected, proper diagnostic measures including
a dark field examination should be done before treatment is started and the blood serology
repeated monthly for at least four months.
In long term therapy, periodic laboratory evaluation of organ systems, including haematopoietic,
renal and hepatic studies should be performed.
If doxycycline is used to treat infections due to group A beta-haemolytic streptococci, treatment
should continue for at least 10 days.
Abnormal hepatic function has been reported rarely and has been caused by both oral and
parenteral administration of tetracyclines, including doxycycline.
As with other tetracyclines, doxycycline forms a stable calcium complex in any bone forming
tissue. A decrease in fibula growth rate has been observed in pre-matures given oral
tetracycline. This reaction was shown to be reversible when the medicine was discontinued.
Photosensitivity manifested by an exaggerated sunburn reaction has been observed in some
individuals taking tetracyclines. Treatment should be discontinued at the first evidence of skin
The use of Doxy may occasionally result in overgrowth of non-susceptible organisms. If a
resistant organism appears, the antibiotic should be discontinued, and appropriate therapy
instituted. In long term therapy, because tetracyclines have been shown to depress plasma
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prothrombin activity, patients who are on anti-coagulant therapy may require downward
adjustment of their anti-coagulant dosage.
Increased Intracranial Pressure
The use of tetracyclines in infants, even in the usual therapeutic doses, may cause increased
intracranial pressure and bulging of the fontanelles. Discontinuation of therapy results in prompt
return of the pressure to normal.
Interaction with other medicines and other forms of interaction
Doxy may interfere with the bacterial effect of penicillins and vice versa.
There have been reports of prolonged prothrombin time in patients taking warfarin and
doxycycline. Because the tetracyclines have been shown to depress plasma prothrombin activity,
patients who are on anticoagulant therapy may require downward adjustment of their
The concurrent use of tetracyclines and methoxyflurane has been reported to result in fatal
There have been anecdotal reports that concurrent use of tetracyclines may render oral
contraceptives less effective.
Antacids and Iron preparations
Antacids containing aluminium, calcium or magnesium, or other medications containing these
cations; bismuth salts; and preparations containing iron impair absorption and should not be
given to patients taking doxycycline.
Medicines reducing doxycycline concentrations
Plasma levels of doxycycline are reduced by the ingestion of alcohol or the administration of
barbiturates, anticonvulsants (phenytoin, carbamazepine), disodium hydrogen edetate, sodium
bicarbonate, sodium lactate, acetazolamide and ethoxzolamide.
Fertility, pregnancy and lactation
The importance of this in humans is not known, however, Doxy should not be used in pregnant
women unless the benefit outweighs the risk (refer to section 5.3).
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Doxy has been found in the milk of lactating women it should not be used in nursing mothers.
Refer to section 5.3.
Effects on ability to drive and use machines
The effect of doxycycline on the ability to drive or operate heavy machinery has not been
studied. There is no evidence to suggest that doxycycline may affect these abilities.
More Common Reactions
Skin and subcutaneous tissue: Photosensitive skin reactions (see section 4.4), erythematous
rash, maculopapular rash, morbilliform rash, pustular rash, urticaria, photo-onycholysis and
discolouration of the nails.
Gastrointestinal: Nausea, anorexia, vomiting, dysphagia, diarrhoea, oesophagitis, oesophageal
ulceration, abdominal pain, glossitis, black hairy tongue.
Hypersensitivity reactions: Urticaria, exacerbation of systemic lupus erythematosus.
Hepatic: Cholestatic hepatitis, fatty liver degeneration.
Renal: Dose related increase in serum urea.
Musculoskeletal: Tooth discolouration, enamel hypoplasia.
Others: Bulging fontanelles have been reported in young infants following full therapeutic
dosage. The sign disappeared rapidly when the drug was discontinued.
When given over prolonged periods, tetracyclines have been reported to produce brown-black
microscopic discolouration of thyroid glands. No abnormalities of thyroid function studies are
known to occur.
Less Common Reactions
Gastrointestinal: Enterocolitis (see section 4.4), inflammatory lesions (with monilial overgrowth)
in the anogenital region; dyspepsia and pseudomembranous colitis (see section 4.4); C. difficile
Hepatic: Abnormal hepatic function has been reported rarely (< 1 in 1000), hepatotoxicity.
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Skin and subcutaneous tissue: Exfoliative dermatitis; Stevens-Johnson syndrome, Toxic
Epidermal Necrolysis (TEN).
Musculoskeletal: Arthralgia; myalgia.
Renal: Acute renal failure.
Hypersensitivity reactions: Angioneurotic oedema, anaphylaxis, anaphylactic shock,
anaphylactic reaction, anaphylactoid purpura, serum sickness, pericarditis, hypotension,
dyspnoea, peripheral oedema, tachycardia, erythema multiforme.
Blood and lymphatic system: Leucopenia, thrombocytopenia purpura, increase in prothrombin
time, haemolytic anaemia, eosinophilia.
Nervous system: Flushing, malaise, headache, confusion, taste loss, stupor, hypoaesthesia,
paraesthesia, somnolence, benign intracranial hypertension in adults, increased intracranial
pressure in infants.
Eye: Conjunctivitis, periorbital oedema.
Psychiatric: Depression, anxiety, hallucination.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicine is important. It allows
continued monitoring of the benefit/risk balance of the medicine. Healthcare professionals are
asked to report any suspected reactions https://nzphvc.otago.ac.nz/reporting/
No reports of overdosage have been received.
If such a case occurs, treatment requires discontinuation of Doxy and use of symptomatic
For advice on the management of overdose please contact the National Poisons Centre on 0800
POISON (0800 764766).
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Pharmacotherapeutic group: Tetracyclines, ATC code: J01AA02
Mechanism of action
Doxycycline is a broad-spectrum antibiotic that is primarily bacteriostatic. It is thought to exert
its antimicrobial effect by inhibition of protein synthesis. It prevents the binding of amino-acyl-
tRNA to the messenger RNA-30S ribosomal subunit. The binding of fMet-tRNA is especially
sensitive. As a result, initiation, and therefore polyribosome formation, are blocked. Doxycycline
inhibits only rapidly multiplying organisms.
Doxycycline is virtually completely absorbed after oral administration of either tablets and the
absorption is not notably influenced by the ingestion of food or milk.
Peak serum levels of approximately 2.6 mcg/ml are achieved at 2 hours following a 200 mg
tablet dose. Doxycycline diffuses readily into most body tissues, fluid and/or cavities and the
volume of distribution has been measured as 0.7 L/kg. Plasma protein binding is variable.
Bioformation and Elimination
Doxycycline is concentrated by the liver in the bile. It is also excreted in the urine as the
unchanged medicine in high concentration. The serum half-life of doxycycline ranges from 18-22
hours and this is not altered by severe renal failure, haemodialysis, age or hepatic failure.
Preclinical safety data
Animal studies conducted in rats and mice have not provided conclusive evidence that
tetracyclines may be carcinogenic or that they impair fertility. In two mammalian cell lines,
positive responses for mutagenicity occurred at concentrations of 60 and 10 mcg/ml
respectively. In humans no association between tetracyclines and these effects have been made.
Results of animal studies indicate that tetracyclines cross the placenta, are found in foetal
tissues and have toxic effects on the developing foetus manifested by retardation of skeletal
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List of excipients
Doxy-50 and Doxy-100 tablet contains colloidal silicon dioxide, magnesium strearate, maize
starch, microcrystalline cellulose, Opadry white Y-1R-7000B.
24 months in bottles and 36 months in blister.
Special precautions for storage
Store at or below 30°C. Protect from light.
Nature and contents of container
Doxy-50 tablets: 30 tablets in a bottle; 30 tablets or 7 tablets in blister pack
Doxy-100 tablets: 100 tablets in a bottle
Not all strengths or pack sizes may be marketed.
Special precautions for disposal and other handling
Any unused medicine or waste material should be disposed of in accordance with local
Douglas Pharmaceuticals Ltd
P O Box 45 027
Phone: (09) 835 0660
DATE OF FIRST APPROVAL
Doxy-50 tablets: 17 May 1996
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Doxy-100 tablets: 08 Aug 1980
DATE OF REVISION OF THE TEXT
22 January 2019
Summary table of changes
Summary of new information