Pharmacology and toxicology
Baclofen, carisoprodol. chlormezanone, Clostridium botulinum toxin, dantrolene, fenyramidol, mephenesin, methocarbamol, orphenadrine, pridinol, quinine ethylcarbonate, tetrazepam, tizanidine, and tolperisone are available for treating muscle tension. There are anecdotal reports of normal pregnancy outcomes, but also of withdrawal syndromes (especially convulsions) after bacolofen treatment during pregnancy. There are five case reports on intrathecal baclofen therapy: three patients were treated throughout the whole pregnancy. All five newborns were healthy and did not show withdrawal symptoms (Roberts 2003, Munoz 2000). In two eases, 20-80mg was taken orally throughout the whole pregnancy. Again there were no malformations, but both children suffered from withdrawal - one with seizures on day 7 (Ratnayaka 2001). The other newborn showed hyperirritability and respiratory problems (Moran 2004).
Following the use of chlormezanone during pregnancy, a fulminating hepatitis with a liver transplant and the birth of a healthy child has been reported (Bourliere 1992).
The available experience with the use of the other older and outdated treatments in pregnancy is not sufficient for a risk assessment.
Recommendation. Myotonolytics are relatively contraindicated during pregnancy, and should be reserved for very special indications - e.g. dantrolene for malignant hyperthermia. Physiotherapeutic measures and antiinflammatory agents or antirheumatics are preferable. In certain cases, the tension-releasing action of the better-studied diazepam can be used. Exposure to the myotonolytics mentioned does not require either a termination of the pregnancy or invasive diagnostic procedures.
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