TY  - CHAP
M1  - Book, Section
TI  - PYRIDOXINE (VITAMIN B6)
A1  - Kearney, Thomas E.
A2  - Olson, Kent R.
A2  - Anderson, Ilene B.
A2  - Benowitz, Neal L.
A2  - Blanc, Paul D.
A2  - Clark, Richard F.
A2  - Kearney, Thomas E.
A2  - Kim-Katz, Susan Y.
A2  - Wu, Alan H. B.
PY  - 2018
T2  - Poisoning & Drug Overdose, 7e
AB  - Pharmacology.  Pyridoxine  (vitamin  B6)  is  a  water-soluble  B-complex  vitamin  that  acts  as  a  cofactor  in  many  enzymatic  reactions.  Overdose  involving  isoniazid  or  other  hydrazines  (eg,  Gyromitra  mushrooms,  rocket  propellant,  or  fuel-containing  hydrazine,  mono-,  or  di-methylhydrazine)  may  cause  seizures  by  interfering  with  pyridoxine  utilization  in  the  brain,  and  pyridoxine  given  in  high  doses  can  control  these  seizures  rapidly  and  may  hasten  consciousness.  It  can  also  correct  the  lactic  acidosis  secondary  to  isoniazid-induced  impaired  lactate  metabolism.  In  ethylene  glycol  intoxication,  pyridoxine  may  enhance  metabolic  conversion  of  the  toxic  metabolite  glyoxylic  acid  to  the  nontoxic  product  glycine.  Pyridoxine  is  well  absorbed  orally  but  usually  is  given  intravenously  for  urgent  uses.  The  biological  half-life  is  about  15–20  days.IndicationsAcute  management  of  seizures  caused  by  intoxication  with  isoniazid,  hydrazines,  Gyromitramushrooms,  or  possibly  cycloserine.  Pyridoxine  may  act  synergistically  with  diazepam.Adjunct  to  therapy  for  ethylene  glycol  intoxication.May  improve  dyskinesias  induced  by  levodopa.Contraindications.  Use  caution  in  patients  with  known  sensitivity  to  pyridoxine  or  parabens  preservative.Adverse  effectsUsually  no  adverse  effects  are  noted  from  acute  dosing  of  pyridoxine.Chronic  excessive  doses  may  result  in  peripheral  neuropathy.Use  of  the  1-mL  vials  may  cause  mild  CNS  depression  owing  to  the  preservative  if  50  or  more  vials  (to  deliver  ≥5  g  of  pyridoxine)  are  administered  (equivalent  to  ≥250  mg  of  chlorobutanol).Preparations  containing  the  preservative  benzyl  alcohol  (eg,  contained  in  some  1-mL  and  the  30-mL  vials)  have  been  associated  with  "gasping"  syndrome  in  premature  infants.Use  in  pregnancy.  FDA  Category  A  (Introduction).  However,  chronic  excessive  use  in  pregnancy  has  resulted  in  pyridoxine  withdrawal  seizures  in  neonates.Drug  or  laboratory  interactions.  No  adverse  interactions  are  associated  with  acute  dosing.Dosage  and  method  of  administrationIsoniazid  poisoning.  Give  1  g  of  pyridoxine  intravenously  for  each  gram  of  isoniazid  known  to  have  been  ingested  (as  much  as  52  g  has  been  administered  and  tolerated).  Dilute  in  50  mL  of  dextrose  or  saline  and  give  over  5  minutes  (rate  of  1  g/min).  If  the  ingested  amount  is  unknown,  administer  4–5  g  IV  empirically  and  repeat  every  5–20  minutes  as  needed.Hydrazine  and  gyromitra  mushroom  poisoning.  Give  25  mg/kg  IV  over  15–30  minutes  for  seizures;  repeat  as  necessary  and  up  to  a  maximum  cumulative  dose  of  15–20  g  daily  has  been  suggested  for  mushroom  poisoning.Ethylene  glycol  poisoning.  Give  50  mg  IV  or  IM  every  6  hours  until  intoxication  is  resolved.Cycloserine  poisoning.  A  dosage  of  300  mg/d  has  been  recommended.FormulationsParenteral.  Pyridoxine  hydrochloride  (various),  100  mg/mL  (10%  solution)  in  1-  and  30-mL  vials  (1-mL  vial  may  contain  the  preservative  chlorobutanol,  and  30-mL  vial  contains  1.5%  benzyl  alcohol).  Note:  Only  one  US  company,  Legere  Pharmaceuticals  (Scottsdale,  AZ;  phone:  1-800-528-3144),  manufactures  and  distributes  the  3-g  (30-mL)  vials.  See  "Adverse  effects"  above  regarding  use  of  the  1-mL  vials.Suggested  minimum  stocking  levels  to  treat  a  100-kg  adult  for  the  first  8  hours  and  24  hours:  pyridoxine  hydrochloride,  first  8  hours:  9  g  or  three  vials  (100  mg/mL,  30  mL  each  or  equivalent);  first  24  hours:  24  g  or  eight  vials  (100  mg/mL,  30  mL  each  or  equivalent).  
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/16
UR  - accessmedicine.mhmedical.com/content.aspx?aid=1174607564
ER  -