A 25 y/o active duty female presents to the Flight Surgery Clinic after a positive PPD and is started on a treatment of "latent infection" (formerly known as prophylaxis) regimen of isoniazid (INH) 300mg once daily and pyridoxine (vitamin B-6) 50mg once daily for 9 months.  She returns to the clinic the next day voicing significant concerns about potential teratogenicity since she is actively attempting to become pregnant.  She does not want to comply with the regimen because she believes the INH poses a significant risk to her fetus if she does in fact become pregnant. The
Flight Surgeon is looking for some solid answers and comes to see the pharmacy for some help. 

What's your answer/advice? Proceed or not? Why or why not?

SELECT  here for discussion

** THANKS to MAJ (Dr.) Andy Meadows for his idea for this Pearl**

Probably proceed.

While the use of any medication during pregnancy should be avoided (if possible), there are times when the risks of the drug to the mother and/or fetus is far outweighed by the benefit(s) of the drug or the risks of not taking the drug. This is probably a situation where the risks of the drug are outweighed by the benefits of the drug or the risks of an active infection with M. tuberculosis.

In this case, after some research the pharmacy determined INH was safe for use during pregnancy and the patient was appropriately re-assured.  She's agreed to comply with her 9-month treatment regimen and is a happy camper.

As stated above, although there are concerns over medication use during pregnancy, untreated TB is clearly a greater risk to both the fetus and the mother and, thus, treatment should be pursued.  INH has been reported to cause teratogenic effects in animals, but not in humans.  Literature reviews show that INH is relatively safe for use during pregnancy, even for a period of 9 months.

The 1993 edition of Applied Therapeutics (4th ed. Page 842, table 38.6) lists the following pregnancy outcomes among women receiving antitubercular therapy vice a normal population.

DRUG              Spontaneous Abortion (%)    Stillbirth (%)    Premature Birth (%) Malformed Infant (%)   
Isoniazid (INH)           0.34                           0.61                  1.88                           1.09   
Ethambutol                 0.16                           0.78                  4.08                           2.19   
Rifampin                    1.67                           2.15                  0.48                           3.35   
Streptomycin              0.97                            0.0                    0.0                          16.91   
Normal Population       6.8                             2.2                     7.1                          1.4-6.0   

(Data compiled from several sources. REF: Snider DE et al. Treatment of tuberculosis during pregnancy. Am Rev Respir Dis. 1980;122:65)