Lorrie Marie Sinkfield sued Shi-Han Oh, M.D., and Gerry Farmer, M.D., her treating obstetricians, after she suffered a miscarriage. Sinkfield challenges the summary judgment in favor of the defendant doctors.
Viewed in the light most favorable to Sinkfield, the non-movant, the evidence was as follows. Sinkfield began treatment with Drs. Oh and Farmer in late November 1992. From the time of her initial visit until the miscarriage on January 19, 1993, Sinkfield at various points complained of amniotic fluid leakage, vaginal bleeding, and abdominal and back pain. Before this pregnancy, she had experienced two prior miscarriages. In the latter part of December, Sinkfield’s heavy bleeding and severe abdominal pain necessitated her hospitalization. On her release date of December 24, Dr. Farmer prescribed Motrin 800 for pain and lifted the total bed rest restriction prescribed by Dr. Oh. Sinkfield subsequently returned to work. On January 19, Sinkfield suffered a miscarriage, delivering a male fetus with a gestational age of 20 to 22 weeks. In the underlying action, she alleged that Drs. Oh and Farmer failed to properly diagnose her medical condition as a high risk pregnancy and failed to provide *884appropriate medical treatment.
Sinkfield’s expert, Verna A. Thornton, M.D., enumerated several deviations from proper care by her treating physicians including: failure to place Sinkfield on a contraction or fetal monitor, failure to prescribe any medication to stop premature contractions, negligently dismissing her from the hospital, failure to perform tests for fetal heart tones, failure to restrict her to complete bed rest with prescribed medicine, failure to test for leaking amniotic fluid and a deviation from the applicable standard of care by prescribing Motrin 800. On deposition, Dr. Thornton attested that prescribing Motrin was inappropriate because one of its side effects is a reduction of amniotic fluid. Five days before her physician prescribed Motrin, an ultrasound test indicated a normal amount of amniotic fluid. When Sinkfield delivered the stillborn fetus a month later, no amniotic fluid was present.
On summary judgment, the defendant physicians contended that even assuming arguendo that they had failed to provide appropriate care and treatment for Sinkfield’s medical condition, Sinkfield failed to offer any evidence showing that their acts or omissions caused her miscarriage. In response, Sinkfield submitted the affidavit of Charles Proctor, Ph.D., a pharmacologist and toxicologist. Dr. Proctor claimed to have expert knowledge of the effects of dosages of Motrin on pregnant women and their fetuses at various stages of pregnancy. Dr. Proctor testified that it was his professional opinion that “the Motrin-800 (ibuprofen, 800 milligrams) prescribed by Dr. Gerry Farmer on December 24, 1992 was the predominate major contributing factor to the demise of the fetus of Lorrie Marie Sinkfield.” According to Dr. Proctor, the fetus’ demise “was precipitated by Motrin-800 (ibuprofen, 800 milligrams) induced Oligohydramnios (deficit in amniotic fluid).”
Finding that Dr. Proctor was not a medical doctor, the trial court rejected Dr. Proctor’s testimony as “incompetent.” The court held that because Sinkfield failed to establish by competent evidence that any breach of the applicable standard of care by the physicians caused or contributed to her injury, the physicians were entitled to summary judgment as a matter of law. Held:
1. The trial court erred in holding that the affidavit of Charles Proctor, Ph.D., was not competent evidence. In this procedural posture, summary judgment, Proctor’s testimony was admissible evidence for the limited purpose for which it was offered — to show causation of the injury. It was not disputed that Dr. Proctor had expert knowledge, as he claimed, about various dosages of Motrin and the drug’s effects on pregnant women and their fetuses. Instead, the defendant physicians asserted that Dr. Proctor was not competent to testify because “he is not a medical doctor, is not licensed to practice *885medicine, nor is he permitted to write prescriptions.”
However, this argument misses the mark because Dr. Proctor’s testimony was not offered to address the applicable standard of care and any breach thereof, but to show causation. If Dr. Proctor, as a toxicologist and pharmacologist, had been offered as an expert witness against the two medical doctors for purposes of satisfying the strictures of OCGA § 9-11-9.1 (a), Dr. Proctor would not have been a competent witness. See Hewett v. Kalish, 264 Ga. 183, 186 (2) (442 SE2d 233) (1994). It is well settled that a professional expert affidavit for pleading purposes under OCGA § 9-11-9.1 (a) in a medical malpractice case must be from a person knowledgeable about the applicable standard of care that has allegedly been breached. See, e.g., Handson v. HCA Health Svcs. of Ga., 264 Ga. 293, 294 (443 SE2d 831) (1994) (allopathic physician competent to testify as to osteopathic physician’s care and skill); Stubbs v. Ray, 218 Ga. App. 420, 421 (1) (461 SE2d 906) (1995) (board-certified general surgeon shared overlapping expertise with defendant radiologist); Crook v. Funk, 214 Ga. App. 213, 215 (2) (447 SE2d 60) (1994) (physician competent to testify about competency of registered nurse).
Georgia law, however, does not mandate that only medical doctors be permitted to testify regarding medical issues; others with certain training and experience may testify on issues within the parameters of their expertise. Goodman v. Lipman, 197 Ga. App. 631, 633 (3) (399 SE2d 255) (1990); OCGA § 24-9-67. As we determined in Goodman, it was reversible error to exclude a pharmacologist’s testimony in a medical malpractice case, where it had been offered as to the effects of particular drugs which had allegedly been improperly prescribed by a cardiologist. We held that the trial court erred in excluding the testimony of the pharmacologist because his testimony about the properties of the drugs at issue was relevant to the case. Id. Compare Chandler v. Koenig, 203 Ga. App. 684, 687 (417 SE2d 715) (1992) (pharmacologist who lacked overlapping professional expertise not competent to testify for purposes of OCGA § 9-11-9.1 (a), regarding the standard of care in the medical profession).
By definition, a pharmacologist is “one who makes a study of the actions of drugs.” The Sloane-Dorland Annotated Medical-Legal Dictionary (1987 ed.). Pharmacology is “the study of drugs as to their chemistry, source, physical properties, preparation and physiological effects on living tissue, whether they be used in therapeutic amounts or otherwise, their absorption, their fats, their excretion and therapeutic indications for their use.” Colusa Remedy Co. v. United States, 176 F2d 554, 558 (8th Cir. 1949). In this case, as in Goodman, Dr. Proctor, as an expert in the fields of pharmacology and toxicology, was competent to testify to the scientific effect of the particular drug at issue. See Jordan v. Sante Fe Engineering, 198 Ga. App. 600, 602-*886603 (2) (b) (402 SE2d 304) (1991) (toxicologist qualified to testify as to the effect of certain substances on the body). We question whether a medical doctor’s pharmacological training is generally comparable to that of a doctor of pharmacology. Thus, it is difficult to see what medically trained professional could have been more qualified to testify about the effects of the particular drug at issue than Dr. Proctor, who had earned a Ph.D. with a double major of pharmacology and toxicology from a prominent university.
Moreover, it is well settled that “[t]he opinions of experts on any question of science, skill, trade, or like questions shall always be admissible; and such opinions may be given on the facts as proved by other witnesses.” OCGA § 24-9-67. Expert testimony, like Proctor’s offered here, is admissible when it is helpful or necessary to prove disputed facts. See Jones v. State, 232 Ga. 762, 764 (2) (208 SE2d 850) (1974). We conclude that it was error to exclude Dr. Proctor’s testimony on the limited issue for which it was offered.
Notwithstanding the physicians’ contention to the contrary, Riggins v. Wyatt, 215 Ga. App. 854, 856 (452 SE2d 577) (1994) neither requires nor authorizes a different result. In Riggins, unlike here, the issue was whether a professor of biomechanics possessed the requisite overlapping expertise to qualify as an expert witness for pleading purposes under OCGA § 9-11-9.1 as to the standard of care applicable to an orthopedic surgeon. We held that he did not, a conclusion unrelated to the instant case. Riggins, 215 Ga. App. at 856.
The dissent misconstrues the meaning of Chandler Exterminators v. Morris, 262 Ga. 257 (2), 258 (3) (416 SE2d 277) (1992), which was overruled in part by an act of the legislature. Effective July 1, 1993, the General Assembly amended OCGA § 43-39-1 to legislatively overrule Chandler Exterminators, supra, to the extent that it held that a neuropsychologist is not qualified to render an opinion concerning the diagnosis of the pathology of organic brain disorders and brain damage. Drake v. LaRue Constr. Co., 215 Ga. App. 453, 455 (2) (451 SE2d 792) (1994). Of course, it is axiomatic that no expert can testify outside the limits of his area of expertise.
2. Sinkfield contends that material issues remain as to whether Dr. Oh’s and Farmer’s treatment proximately caused her injury. She claims that the medical testimony sufficiently showed the parties dispute what caused the miscarriage. We agree. Her expert, Dr. Thornton, testified that although no single factor caused the miscarriage, in her professional opinion, Sinkfield miscarried primarily because of losing amniotic fluid and experiencing pre-term contractions. Dr. Proctor testified that it was his professional opinion that the Motrin 800 caused the deficit in the amniotic fluid and the demise of the fetus.
The dissent’s insinuation that Dr. Proctor’s testimony would not *887be probative evidence to establish the cause of the miscarriage is repudiated by the physicians who concede in their appellate brief that Dr. Proctor’s testimony, if admissible, would be probative as to the issue of the causation of the miscarriage. They acknowledge that “the affidavit of Charles Proctor, Ph.D. . . . addressed the sole allegation that the Motrin prescribed for Ms. Sinkfield by Dr. Farmer caused Ms. Sinkfield’s miscarriage.” They argue, “[o]nce Dr. Proctor’s testimony is disregarded as to whether the Motrin proximately caused Appellant’s miscarriage. . . .”
Moreover, the dissent’s reliance on Sinkfield’s prior medical history is unpersuasive because her next pregnancy, which was carefully monitored and treated as a high risk pregnancy, successfully concluded with the birth of a healthy baby boy. The fact that Sinkfield was threatening a miscarriage before the Motrin was prescribed does not resolve the disputed issue as to whether Motrin precipitated the miscarriage.
Notwithstanding the appellees’ assertion to the contrary, the fact that Dr. Thornton was not able to “conclusively” testify as to the exact cause of the miscarriage does not, without more, prove the absence of proximate causation especially when considered in light of her testimony as a whole. See Lee v. Satilla Health Svcs., 220 Ga. App. 885, 889 (2) (470 SE2d 461) (1996). Compare Bonard v. Lowe’s Home Centers, 224 Ga. App. 85, 87 (2) (479 SE2d 784) (1996). Moreover, Dr. Proctor’s uncontroverted testimony was that Motrin was the main cause of the injury. See Matthews v. DeKalb County Hosp. Auth., 211 Ga. App. 858 (1), 859 (440 SE2d 743) (1994). Based on the record before us, we cannot say that disputed material factual issues regarding causation do not remain.
Judgment reversed.
McMurray, P. J, Pope, P. J., Beasley, Johnson, Smith and Eldridge, JJ., concur. McMurray, P. J., Pope, P. J., Johnson, Smith and Eldridge, JJ., also concur specially. Andrews, C. J., Birdsong, P. J., and Blackburn, J., dissent.