|Are Generic Drugs as
Effective as Brand Name? - Not Always!
A number of
patients with a history of good results on brand name antibiotics began
experiencing difficulties when a generic was substituted. Therefore, if
you have prescribed a brand name tetracycline for a patient using
antibiotic therapy and have not specified d.a.w. or no
substitutions, your patient is probably taking a generic version
and may be having a less than significant response to the treatment.
Some generic versions have been found to be ineffective for this
In order to market drugs, U.S. generic manufacturers must have a
permit and approval from the Food and Drug Administration (FDA) indicating
that the active ingredient is approximately the same as that of the brand
name. The determination of drug approval is made according to whether it
is pharmaceutically equivalent, bio-available,
Two drugs are considered pharmaceutical equivalents when they contain
the same chemically active ingredient(s) and are identical in dosage form
and strength. Tetracyclines such as minocycline are complex with many
properties that may play an important part in treatment response in the
arthritic patient. The fact that patients in remission (sometimes for
years) while on antibiotic therapy saw a gradual return of symptoms when
switched to a generic alerted us to a potential problem with some
generics. In three test patients, these symptoms began to reverse
immediately upon a return to the brand name version of the drug.
Pharmaceutical equivalence may be affected by many things.
1) variations in inert ingredients
2) plants in different parts of the world
may produce ingredients that vary in quality, and by batch and
manufacturing methods. Until recently, 80% of drug ingredients came from
plants in Western Europe. According to a NY Times article April 11,
1996, that is changing. Many ingredients are now being used from plants in
China, Japan, South Korea, India and Eastern Europe where they are
produced more cheaply. Bob Milanese, president of the National Association
of Pharmaceutical Manufacturers, indicates that only a handful of these
plants meet FDA standards. "Some others are questionable" due to the
difficulty in finding people and budget to "get over and inspect these
plants." Another factor which affects generic quality cited by the same
article is the international buy outs and diversification allowing the
combination of questionable ingredients into generic production.
3) In oral drugs, capsule content may be 7% over or 7% under the stated
content, e.g. a 100 mg. capsule may be as low as 93 mg. or as high as 107
4) Manufacturers may shift their source of supply.
5) Once a drug has been approved by the FDA, manufacturers sometimes
make changes to the formula which was originally submitted.
6) Many arthritic patients are elderly. The age of the patient may be a
factor in pharmacokinetics. Digestive tract absorption of an oral drug may
be altered by a variety of factors, including higher gastric pH,
accelerated gastric emptying, and thinning and reduction of the absorptive
surface. Bioavailability may be influenced by the increase (or decrease)
in percent of body fat which is common in some with age. It may be even
higher in sedentary persons (or persons in pain who are inactive in order
to minimize discomfort.) This increased fat to lean ratio results in a
reservoir for lipid-soluble drugs which is larger allowing those drugs to
stay in the body longer, increasing the possibility of drug sensitivity by
prolonging the half-life. Conversely, total water content declines with
age. This decline allows a decreased volume of distribution for
In addition to general approval, the FDA rates drugs with codes. All
drugs with an "A" code are rated as being therapeutically equivalent;
"B" coded drugs are those not rated equivalent Some pharmacies fill
with B-rated drugs. At this time, it is recommended that no patient use a
version of a drug with a B-rating. Clinical differences or serious
bioequivalence problems with B-rated products have been reported for drugs
such as prednisone, estrogen tablets, levodopa and phenytoin. In addition
to The Orange Book, The Physician's Generix lists available
generics as therapeutically equivalent or non-equivalent. Because the
antibiotic protocol uses such low doses, leeway between versions which are
effective and those which are not may be much more critical.
In bioavailability, it can be assumed that the drug's effectiveness is
related to the amount of product absorbed and the speed of
absorption. However, in some cases, the pharmaceutically equivalent
products can have different bioavailability. They may be absorbed either
faster or slower than the brand name drug which may or may not be
The pH-dissolution profile of a product may have clinical relevance.
Even if the coating is adequate to prevent release of the enzymes in the
stomach where the ingredients are irreversibly inactivated, it may not
dissolve at the pH of the duodenum after meals.
In bioequivalence studies, the goal of testing is to determine if the
drugs are functionally equivalent. The FDA requires that any approved drug
be effective within a 20% range of the original patented or brand name
drug. This means that the effectiveness may be 20% greater or 20% less
effective than the brand name so that two generic drugs could contain as
much as a 40% difference from each other. Therefore, a drug may be legally
chemically equivalent but not at the same time
clinically equivalent. A study run on a generic of the
anti-seizure, Tegretol, found the generic allowed breakthrough seizures.
An example of how the above factors may affect the bioavailability and
clinical effectiveness is seen by applying these factors to tetracycline.
At one extreme, a 500 mg. dose of tetracycline taken in 2-250 mg. capsules
which is 20% lower in effectiveness, 7% low in the mg. amount in each
capsule (14% dose total) and which is taken with food, decreasing the
absorption rate (<50%), could provide as low as 136 mg of tetracycline
that is available to the body. Correspondingly, the same 2-250 mg.
capsules making a total dose of 500 mg. which is 20% more effective, 7%
over on mg. in capsule and taken without food (increasing the absorption
rate to 77%), provides 555 mg that is functionally available to the
system. It should be noted the food-drug interaction is less a factor with
minocycline and doxycycline as they are absorbed differently.
In addition to the ±20% difference allowed in bioavailability by the
FDA and the ±7% of the stated capsule content allowed by the U.S.
Pharmacopoeia, there are other considerations which should be considered
when using a generic drug.
1) Some drugs lose potency while on the shelf, so drug companies
increase the strength so as the drug ages, it will still provide a
therapeutic level. This means patients who use the drug soon after
production when the dose may be stronger may be getting an overdose.
2) There is a risk that a generic substitution could result in a change
in serum concentration
3) Such a change may lead to signifi-cant adverse effects or loss of
4) The risk that patients may receive different generics each time they
fill their prescription, changing the response to the drug.
5) Cost of brand names is usually, but not always, higher than for a
6) Blood tests can become necessary to determine adequate
concentrations, excessive, possibly toxic concentrations or low, possibly
7) The cost of the time and effort spent in adjusting the dose (if
Bioequivalence may be effected by the type of study; e.g. two brand
name pharmaceutical equivalents were each compared with a placebo in
separate trials but were not compared with each other for
bioequivalence. Thus while each was effective, it cannot be assumed that
they produce the same clinical effect. Bioequivalence studies are
performed on healthy volunteers and thus may not account for the full
pharmacologic and therapeutic impact of generic substitution on patients
A pharmacist may legally fill a prescription in the United States with
either the brand name or a generic without consulting either
the patient or the physician. A prescription may not even be filled
consistently with the same generic. To assure continuity for the patient,
the physician should indicate on the prescription no substitutions
or dispense as written (daw).
The purpose of this article is not to condemn generic drugs for many
are as effective as the brand name and even come from the same
manufacturing company, but are repackaged and sold by another company as
their own generic brand. Our purpose is, however, to provide a warning
not to assume that all drugs with the same generic title are equal and
will have the same clinical effect, even though many drug reps say they
are equal. This is particularly true of the tetracycline family
because it is one of the oldest families of antibiotics being first
patented in 1953. Since a patent is good for 17 years, the original
tetracycline has been available for generic reproduction for some 25
Brooke PA, Resistant Prices, A study of competitive strains in the
antibiotic markets, 1976, Ballinger Pub.
Hendeles L, Hochhaus G, Kazerounian S, Generic and alternative
brand-name pharmaceutical equivalents: Select with caution, Am J Hosp
Pharm, 1993; 50:2, 323-329.
Medical Information Department, Lederle Labs, telephone conversations.
Mandell GL, Douglas RG, Jr., Bennett JE, Principals and Practice of
Infectious Diseases, Wiley Medical Pub, 1985.
Mikati M, Bassett N, Schachter S, Double-blind randomized study
comparing brand-name and generic phenytoin monotherapy, Epilepsia,
1992; 33:2, 359-364.
Oles KS, Penry JK, Smith LD, Anderson RL, Dean, JC, Riela AR,
Therapeutic bioequivalency study of brand name versus generic
carbamazepine, Neurology, 1992, 42:6, 1147-52.
Physician's Generix?, Data Pharmaceutica, 1996.
Reinstein PH, Regulatory status of pancreatic enzyme preparations,
JAMA, 1990; 263:18, 2491-2492.
Stoughton RB, Are generic formulations equivalent to trade name topical
glucocorticoids? Arch Derm, 1987; 123:9, 1312-1314.
Univ. of Chicago Drug Information, telephone conversation.
For insurance companies who will not cover brand name drugs when a
generic is available, a blood test to determine concentration may be
necessary for those using low dose antibiotics to provide data to require
payment for the brand name drug.
To assure continuity for the patient, the physician should indicate on
the prescription no substitutions or dispense as written (daw).