Last update Oct. 11, 2017


High Risk

Poorly safe. Evaluate carefully. Use safer alternative or interrupt breastfeeding 3 to 7 T ½ (elimination half-lives). Read the Comment.

Centrally-acting muscle relaxant with sedative properties. Administered orally.
It has pharmacokinetics with rapid absorption and elimination (PDR 2017, Prompila 2007, Desiraju 1983).

Since the last update we have not found published data about its excretion in breast milk.

Its pharmacokinetic data (low molecular weight, low protein binding, small volume of distribution) make its likely that it could pass into breast milk in quantities that could be significant.

If you have to use it during breastfeeding, you should monitor sedative effects in the baby. To minimize exposure, medication can be taken just after a feed and waiting 3-4 hours before breastfeeding again.


  • Baclofen ( Safe. Compatible. Minimal risk for breastfeeding and infant.)
  • Carisoprodol (Possibly safe. Probably compatible. Mild risk possible. Follow up recommended. Read the Comment.)
  • Methocarbamol (Possibly safe. Probably compatible. Mild risk possible. Follow up recommended. Read the Comment.)

Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

Your contribution is essential for this service to continue to exist. We need the generosity of people like you who believe in the benefits of breastfeeding.

Thank you for helping to protect and promote breastfeeding.

José María Paricio, founder of e-lactancia.

Other names

M03BB03 is Chlorzoxazone in ATC Code/s.

Is written in other languages:


M03BB03 belongs to this group or family:


Main tradenames from several countries containing M03BB03 in its composition:


Variable Value Unit
Oral Bioavail. 100 %
Molecular weight 170 daltons
Protein Binding 13 - 18 %
VD 0.5 ± 0.1 l/Kg
Tmax 2 ± 0.8 hours
1.1 ± 0.5 a 1.5 ± 0.3 hours


  1. PDR. Chlorzoxazone (Lorzone). Drug Summary. 2017 Full text (link to original source) Full text (in our servers)
  2. Prompila N, Wittayalertpanya S, Komolmit P. A study on the pharmacokinetics of chlorzoxazone in healthy Thai volunteers. J Med Assoc Thai. 2007 Abstract
  3. Desiraju RK, Renzi NL Jr, Nayak RK, Ng KT. Pharmacokinetics of chlorzoxazone in humans. J Pharm Sci. 1983 Abstract

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