ANTIBIOTIC DOSAGES AND INTERACTIONS

Please refer to the current edition of the British National Formulary for a comprehensive list of interactions.  Where additional local guidance relevant to interactions with anti-infectives is available, it will be listed below:

The following adult doses are recommended for each of the antibiotics in the preceding text (unless already specified).

  • Drug dosages may require to be modified in the event of renal/hepatic impairment resulting in altered drug clearance.

  • If in doubt – contact the Medicines Information Service (Ninewells Hospital, Extension 32351) or discuss with the Clinical Pharmacist attached to your ward or unit.

  • Where available, oral antibiotic therapy is preferred, unless stated in the text or if the oral route is compromised.

  • If intravenous therapy is initially considered essential, the opportunity for early IV to oral switch (click here for IV/Oral Switch Policy) should be taken (review every 24 hours at least) once resolution of severe acute infection is apparent.

  • For surgical prophylaxis dosages see separate guidance

  • For antibiotic dosing in obesity guidance click here

Aciclovir
Varicella/Shingles  800mg po 5 times per day
Standard IV dose  5mg/kg 8-hourly
High dose IV   10mg/kg 8-hourly
Amikacin - must be approved by ID/Microbiology prior to use
Amikacin Prescribing Guidance

Amoxicillin
Standard IV/PO dose 500mg – 1g po 8-hourly
Mild to moderate Community Acquired Pneumonia (click here) 1g 8-hourly
High dose IV therapy for meningitis in adults if Listeria suspected
2g 6-hourly
Endocarditis see suspected endocarditis section

Ampicillin
Use IV Amoxicillin instead    

Azithromycin  Click here for NICE review of cardiovascular risk
Adult CF Click here for dosing guidance
HIV Click here for dosing guidance


Aztreonam 

Appropriate Use of Aztreonam Click here

Benzylpenicillin
(Oral absorption is poor – administered by injection only)
Standard IV/IM dose    1.2g (2 MU) 6-hourly

Caspofungin - must be approved by ID/Microbiology prior to use
Please refer to NHS Tayside Antifungal guidance Click here

Ceftriaxone
Standard dose 1g IV once daily
Severe infections/high dose 2g IV once daily
Meningitis dose  2g 12-hourly

Chloramphenicol
Eye drops (0.5%) in conjunctivitis – 2-hourly for 2 days reduced to 4 times a day.  Chloramphenicol 1% eye ointment can be applied alone 3-4 times daily at this stage or administered at night in combination with eye drops.  Continue to treat for 2 days once resolution of infection occurs.

Chloroquine
Treatment of Non-falciparum Malaria Click here for dosing guidance
Click here for information on chloroquine base

Clarithromycin
Standard IV/PO dose 500mg 12-hourly

Colistin/Colomycin
Dosing in carbapenem resistant infections (ID/Micro only) Click here for guidance (right click and open in new tab)
Dosing in Adult CF patients Click here for guidance

Co-trimoxazole
Infections other than PCP


PCP

Dose in renal impairment

 960mg bd (can be increased to 1.44g bd in severe infections)

see PCP guidance

  • CrCl >30mL/min - standard dose
  • CrCl 15-29mL/min - 480mg bd
  • CrCl <15mL/min - not recommended (however there is a dose stated in renal drug handbook - ask pharmacist)

Interactions: digoxin, warfarin, phenytoin, other medicines that cause hyperkalaemia, ciclosporin, methotrextate

NB. Co-trimoxazole contains sulfumethoxazole and trimethoprim in combination.  In some cases trimethoprim may be used on its own.  Check sensitivities or micro advice.

Daptomycin - must be approved by ID/Microbiology prior to use
Click here for Daptomycin prescribing guidance

Doxycycline (oral only)
Standard oral dose (eg COPD or CAP) 200mg po stat then 100mg po once daily or twice daily
Lyme Disease 100mg bd
Animal Bites (if penicillin allergic) 100mg bd (in combination with metronidazole)
MRSA  100mg bd

Ertapenem
IV infusion only 1g once daily

Erythromycin
Oral dose 500mg 6-hourly
IV dose Use clarithromycin IV (see above)
Splenectomy patients life long prophylaxis 250mg – 500mg once daily


Fidaxomicin – must be approved by ID/Microbiology prior to use
Recurrent C. difficile Infection Click here for guidance 
Click here for Fidaxomicin administration via NG tube

Flucloxacillin
Standard IV/PO dose   1g 6-hourly
High dose or very obese patients 2g IV 6-hourly
Endocarditis see suspected endocarditis section

Fosfomycin Oral (unlicensed)
Extended spectrum beta-lactamase UTI 3g stat in women, repeat this dose after 3 days for men.  See guidance.
Other indications Seek guidance from Microbiology or ID.

Fusidic acid
Not routinely recommended in NHS Tayside. May be prescribed on advice of ID Specialist or Microbiology

Caution: potentially fatal rhabdomyolysis if prescribed with statins.
Refer to Drug Safety Update, Volume 5, Issue 2, September 2011 for further information.

Gentamicin  Right click here for Ideal Body Weight Table (right click and open in new tab)
Endocarditis 1mg/kg 12-hourly adjusted according to levels. Click here for link
Gram negative sepsis 7mg/kg extended interval regime (see protocol)
Extended interval therapy not appropriate: 2.5mg/kg 12-hourly or 1.5mg/kg 8-hourly
Seek advice from pharmacist re levels
Surgical prophylaxis See prophylaxis section
Pregnancy See obstetrics guide

Immunoglobulin
Click here for guidance

Levofloxacin (IV only)
Standard dose 500mg 12-hourly

Linezolid   Click here for Linezolid prescribing guidance
Oral/IV dose 600mg 12-hourly
100% bioavailability therefore IV should only be used in patients where oral route unavailable.

Meropenem - must be approved by ID/Microbiology prior to use.
Standard IV dose 1g 8 hourly
Cystic Fibrosis click here for protocol

Metronidazole
Standard oral dose    400mg 8-hourly
Rectal dose  1g 8-hourly
Intravenous dose   500mg 8-hourly
Pelvic Inflammatory Disease   see protocol
H pylori infection see guidance
C difficle infection see guidance
Animal bites (if penicillin allergic) 400mg 8-hourly (in combination with doxycycline)

Nitrofurantoin - use with caution if eGFR <45mL/min.  Short courses (3-7 days) may be considered at eGFR of
30-44 mL/min.  See MHRA guidance here
Lower UTI women 50-100mg po 6-hourly
Prophylaxis of UTI (maximum 6 months treatment - see guidance from Respiratory MCN) 50 -100mg po at night or post coital

Ofloxacin (oral only)
Standard oral dose 400mg po once daily or 200mg po 12-hourly
Pelvic Inflammatory Disease see protocol

Phenoxymethylpenicillin (Penicillin V)
Standard oral dose 500mg 6 hourly or 1g 12-hourly
Splenectomy life long prophylaxis 250mg – 500mg 12-hourly

Piperacillin + Tazobactam
Standard IV dose 4.5g 8-hourly
Severely ill patients/neutropenic patients 4.5g 6-hourly

Pivmecillinam: - No dose change is required in mild to moderate CKD. Pivmecillinam may be used as an alternative in the management of UTI where CKD exists (link to policy) or where proven sensitivities are available. It should not be considered as an empiric choice for the management of uncomplicated UTI.
Uncomplicated lower UTI in women >40kg (unlicensed) 400mg 8 hourly for 3 days
UTI or bacteriuria in pregnancy (unlicensed) 400mg 8 hourly for 7 days
UTI in children <40kg (3 months onwards) 20-40mg/kg/day in 3-4 divided doses
Lower UTI in uncatheterised male (unlicensed) 400mg 8 hourly for 7 days
Multi-resistant UTI (e.g. ESBL) if not systemically unwell and proven sensitivities (unlicensed) 400mg 8 hourly for 3 days (females) or 7 days (males)
Oral step down for pyelonephritis or urosepsis (if proven sensitivity) (unlicensed) 400mg every 8 hours

Posaconazole
NOTE: liquid and tablets are note interchangeable - always state the formulation on the prescription and check the dosage For Haematology/Oncology patients click here
For all other patients click here

Pristinamycin (unlicensed) - must be approved by ID/Microbiology prior to use.
Click here for Pristinamycin prescribing guidance Click here for Pristinamycin SPC

Quinine
Treatment of Falciparum Malaria Click here for dosing and monitoring guidance

Rifampicin
MRSA

300mg 12-hourly
Do not use as monotherapy  

Sodium Fusidate (Fusidic Acid) - never use as monotherapy
Standard dose 500mg 8-hourly  
 click here for MRSA guidance

Teicoplanin
Bone and joint infections
 (treated as outpatients)              

 click here for guidance
Neutropenic Sepsis click here for guidance
All other infections Follow guidance in SPC - click here  

Temocillin

ESBL UTI

 2g bd
CF patients up to 2g three times daily

Tigecycline - this antibiotic must never be prescribed without prior authorisation by ID or Microbiology
In September 2013 the FDA issued a warning of increased risk of death when IV tigecycline is used for both approved and non-approved indications.   Click here for FDA guidance.

ID or Microbiology will consider all alternative antibiotic options but if this antibiotic is required the medical team responsible for the patient should ensure their clinical condition is very closely monitored.

Tobramycin
Cystic Fibrosis Click here for guidance.

Trimethoprim
Lower UTI women 200mg po 12-hourly
Uncatheterised male UTI 200mg po 12-hourly
Prophylaxis of UTI    100mg po at night
MRSA in combination with rifampicin 200mg po 12 hourly

Valaciclovir
Varicella/Shingles 1g po 8-hourly for 7 days
Herpes simplex 500mg 12 hourly for 5 days

Valganciclovir (oral only)
CMV retinitis 900mg 12 hourly for 21 days then 900mg daily
Prevention of CMV in transplant patients 900mg daily for 100 days. In kidney transplant patients, prophylaxis may be continued until 200 days post-transplantation.   

Vancomycin  Right click here for Ideal Body Weight Table (right click and open in new tab)
Intermittent IV infusion - usual choice for all adult patients Dosage guidelines see vancomycin protocol
Continuous IV infusion (ICU patients or ID/Micro recommendation only)
 Click here for SAPG guidance (right click and open in new tab)
Oral C difficile infection only - see guidance
Via nasogastric tube

C difficile infection only - see guidance

The solution from a reconstituted injection vial can be administered via an NG tube.  The solution in the vial is stable in the fridge for up to 24 hours.

Rectal instillation (unlicensed)

 

C difficile infection only - see guidance

500mg in 100ml 0.9% sodium chloride every 6 hours as retention enema.  Clamp rectal tube for 1 hour with each dose.  Measure plasma vancomycin levels after 24-48 hours if patient has renal impairment.  If the level is above 10mg/l discuss with ID/Micro and consider discontinuing rectal vancomycin.

Voriconazole - must be approved by ID/Microbiology prior to use.
 Click here for Educational Risk Minimisation Materials
40kg and over 400mg po 12-hourly for 2 doses then 200mg po 12-hourly
under 40kg 200mg po 12-hourly for 2 doses then 100mg po 12-hourly
IV dose            6mg/kg 12-hourly for 2 doses then 4mg/kg 12-hourly

 

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