Pharmacology Review à Exam 2

Antibiotic	Brand Name	Dose Regimen	Cost	Notes
Azithromycin	Zithromax	Day 1 à 500 mg Days 2-5 à 250 mg	$49 for 5 days	Macrolide
Clarithromycin	Biaxin	250-500 mg bid for 7 days	$35 for 7 days	Macrolide
Erythromycin	Generic	250-500 mg bid to qid for 7 days	$7 for 7 days	Macrolide Increase in # of drug interactions Disappearing from use
Amoxicillin	Amoxil	500 mg tid for 7 days	$11.50 for 7 days
Amoxicillin	Generic	500 mg tid for 7 days	$6.51 for 7 days	Equally effective as Amoxil
Amoxicillin + Clavulanate	Augmentin	500 mg tid for 7 days	$73.08 for 7 days	Clavulanate is b-lactamase inhibitor Clavulanate increases efficacy
Penicillin VK	Generic	500 mg qid for 7 days	$2 for 7 days

There are many choices of brand name agents for any particular class of antibiotics

Class	# of Choices	Notes
Penicillins	12	Dental infections are typically best managed with this class à penicillin VK, amoxicillin, Augmentin, Ampicillin Penicillin allergy à indicates allergy to all in same class Penicillin Allergy à ~15% cross reactivity w/ cephalosporins
Macrolides	6	Azithromycin, Clarithromycin, Erythromycin
Cephalosporins	19	Keflex à a broad spectrum, long acting antibiotic Cephalexin à a broad spectrum antibiotic Often recommended by physicians for dental prophylaxis Often the antibiotic of choice for treating severe staphylococcal infections such as endocarditis Not affected by b-lactamase
Fluoroquinolones	9	Broad spectrum Cipro à used for Anthrax
Tetracyclines	8	Doxycycline Minocycline, Tetracycline
Sulfonamides	2	Sulfamethoxazole
Aminoglycosides	6	Indicated in severe systemic infections Amikacin, Gentamycin, Kanamycin, Tobramycin
Miscellaneous	6	Clindamycin is a good alternative Anaerobic infections respond well to metronidazole Others include chloramphenicol, rifampin, vancomycin

Classes of Penicillins

Class	Examples	Notes
Natural Penicillins	Pen G (injected) à Aqueous, Procaine, Benzathine Pen V Phenethicillin
Penicillinase Resistant	Methicillin Nafcillin Cloxacillin Dicloxicillin Oxacillin	Penicillinase is produced by bacteria (which normally breaks down penicillin) This class is not broken down
Aminopenicillins	Ampicillin Amoxicillin Bacampicillin Cyclacillin
Anti-pseudomonas	Aziocillin Cabenicillin Ticarcillin Pipercillin	Not common in dentistry Extended Spectrum

Characteristics of Penicillins

Also known as beta-lactams because the basic structure is susceptible to b-lactamase (which is the same as penicillinase)

Many are combined with a b-lactamase inhibitor such as clavulanate (amoxicillin + clavulanate = Augmentin)

They target gram-positive (narrow spectrum, limited gram-negative coverage)

Relatively greater allergic potential (and I.V. or I.M. > oral)

First line agents in fighting dental infections

About a 15% cross reactivity with some cephalosporins

Nearly 100% renal route of clearance

Contraindicated in patients with renal problems à may show penicillin toxicitiy

Penicillin VK

Most common dosage à 500 mg qid

With therapeutic serum concentrations the action is bactericidal ß often seen on Board Exams

With sub-therapeutic serum concentrations the action is bacteriostatic

Most active against gram-positive cocci à staph, strep

Also effective against bacillis anthracis, clostridium (gangrene, tetanus) and most gram+ anaerobes

Limited activity against selected gram-negative organisms under certain conditions

à bacteroides, streptobacillus, pasteurella, neiseria (pen G is better here)

Most gram-negative bacteria do not have penicillin binding proteins

**Generally classified as narrow spectrum, bactericidal, active against gram-positive

Amoxicillin

Somewhat broader spectrum than penicillin VK

Increased efficacy with b-lactamase inhibitor such as clavulanate

Active against gram-positive (strep, less active against s. aureus) and gram-negative (enterobacteria) organisms

Comparison	Penicillin VK	Amoxicillin
Biologic half life	1.0 hour	1.0 hour
Oral absorption	60-70%	75-90% (superior bioavalability, e.g. more active in bloodstream)
Serum protein bound (used to predict drug interactions; drugs compete for binding sites)	60-80% (a disadvantageàmore drug interactions)	15-20%
Renal elimination	20-40%	60-70%
Use with clavulanate	No	Yes
Absorption with food	Good (suggest taking with water 1 hour prior or 2 hours after meals)	Good
Generic available	Yes	Yes
Aminopenicillin	No	Yes
Max dose per day	7.2 g	4-4.5 g
Antibacterial spectrum	Gram-positive	Broad

n Reasons why amoxicillin is preferred for dental prophylaxis by AHA and AAOS

Amoxicillin Dosing

Maximum amount à 4 g/day

Maximum for severe infections à 875 mg bid

Normal circumstances à sometimes see 500 mg qid, 28 tablets

Accepted dental dose à 500 mg tid, 21 tablets

7 day regime is typical for dental infections

Sub-therapeutic levels are approached at 250 mg tid

Most common regime à 500 mg tid

Manufacturer recommendation à 500 mg bid, or 250 mg tid, or 875 mg bid

Combination Products

Common combinations include the antibiotic plus a b-lactamase inhibitor

Augmentin à amoxicillin + clavulanate

There is also an extended release Augmentin à XR Power (1000 mg released over 12 hours)

Zosyn à piperacillin + tazobactam Na

Unasyn à ampicillin + sulbactam Na

True combinations (two antibiotics) are not common for dental practice

Bactrim, Septra à trimethoprim + Sulfamethoxazole (most common sulfa drug prescribed in dentistry)

Clindamycin (Cleocin) in Dentistry

Antibiotic of choice for patients with a penicillin (including amoxicillin, tetracycline, cephalosporin) allergy

Structure	Unrelated to other agents
Action	Bacteriostatic	Inhibits bacterial protein synthesis (OK with other bacteriostatic, like doxycycline, but not with bactericidal, like penicillins and cephalosporins)
Spectrum	Fairly broad	Best against gram-positive and gram-negative anaerobes Essentially all gram-negative aerobic bacteria are resistant
Indication	Treatment of serious anaerobic infections	We do not typically culture for organism type Usually assume an aerobic bug If pt does not respond, an anaerobic bug may be present and clindamycin is indicated
Contraindications	History of … severe GI disease colitis diarrhea regional enteritis severe hepatic impairment	Does not include GERD May see emergence of clostridium difficile Do Not prescribe anti-diarrheal
Problems	Several problems	Establishing proper use in dentistry Pseudomembranous colitis Management of GI side effects Drug Interactions Dose limits Peptic Ulcers Irritable Bowel Syndrome
Cross allergy	None	Possible exception may be lincomycin
Absorption	90%	Not activated by gastric acid
Serum Binding Protein	92-94%	Very good bioavailability
Biologic Half-Life	2.4-3 hours
Metabolism	Hepatic	Dose reduction in severe hepatic disease
Oral Dose	150-300 mg qid	Much less compared to penicillin and amoxicillin
Max Dose	1.8 g/day	Much less compared to penicillin and amoxicillin
Pregnancy Category	B	Near perfect safety
Caution	Stop drug if persistent diarrhea, abdominal pain, bloody stool

Pseudomembranous Colitis

Most often associated with the use of clindamycin (also some penicillins and cephalosporins)

Suspect this condition if the patient develops severe diarrhea following antibiotic therapy

Positive diagnosis confirmed by stool test for clostridium difficile

Treatment à anti-diarrheals are contraindicated

Drug of choice is Flagyl (metronidazole) à 750-2000 mg/d (3-4 doses, 7-10 days)

Vancocin (vancomycin) as an alternative à 125 mg tid or qid, 7-10 days

As an oral dose à No real systemic effect (not for systemic infections)

Effect is localized in the bowel

Systemic infection requires a parenteral dose

Doxycycline

Available as a Generic	Yes
Antibiotic Class	Tetracycline Derivative (remember these don’t go with dairy foods, and neither do fluoroquinolones, like Cipro)
Mechanism	Bacteriostatic (OK with other bacteriostatic, like clindamycin, but not with bactericidal, like penicillins and cephalosporins)
% Absorption following oral dose	93%
Serum Half-life	18 hrs. (compared to 1 hour for penicillin and amoxicillin, and to 2-3 hours for clindamycin)
Spectrum of Action	Gram-positive and gram-negative
Antimicrobial Dosing	100 mg bid on first day (200 mg loading dose) 100 mg/day thereafter
Contraindication	Hypersensitivity to any tetracycline
Combination Treatment	For recurrent periodontitis 100 mg doxycycline for 5 days 500 mg Augmentin for 5 days Wait at least 1 day for the body to clear the doxycycline Provides superior results vs. doxycycline alone
Other	Doxycycline is found in Periostat in low doses Even with low dose, pts with allergy to tetracyclines will exhibit allergic reaction to Periostat Allergy is not dose dependant

What if a patient has been taking tetracycline 250 mg tid for two years and presents with severe infection?

à Consult with MD to discontinue tetracycline and administer preferred amoxicillin regimen, 500 mg tid, 7 days

(remember that tetracycline is bacteriostatic and may interfere with the bactericidal action of amoxicillin)

à OR, if an anaerobic infection is suspected, the patient could remain on tetracycline and take clindamycin, 300 mg qid, 5 days

(remember that both clindamycin and tetracyclines are bacteriostatic, so there would be no interaction)

Antibiotic Induced Diarrhea

Incidence

Oral Ampicillin à 5-10%

Augmentin à 10-25%

Cefixime (Suprax) à 15-20%

Fluoroquinolones, Macrolides, Tetracyclines à 2-5% (thus popular)

Parenteral shows little or no incidence regardless of antibiotic class

10-20% of antibiotic induced diarrhea is associated with C. difficile

Terms

Nuisance diarrhea à frequent, loose watery stools w/ no complications

Colitis à abdominal cramping, fever, leukocytosis, fecal leukocytes

Mechanisms

Independent of Antimicrobial Action

Erythromycin - á gastric emptying

Clavulanate – á bowel motility

Related to Action on Microbes

Oral dose - â fecal anaerobes

â carb. Metabolism

á osmotic diarrhea

May also see direct action on intestinal mucosa

Management

Usually self-limiting

Discontinue use if severe or persistent

If diarrhea persists after discontinuation suspect C. difficile and treat for 10 days with metronidazole or vancomycin

Often suggested to take yogurt with antibiotics to restore normal flora

(NOT good with fluoroquinolones or tetracycylines)

Antibiotic Allergy

#1 criterion à accept patients version

check history, nature of reaction, suspected agent, distinguish from side effects

Penicillin Allergy

1-10% of patients show adverse drug reaction (ADR)

1% show anaphylaxis

10% show ampicillin induced rash (may be higher and may indicate a true hypersensitivity)

80% of patients who are truly allergic DO NOT SHOW a positive skin reaction

80-90% of penicillin allergies occur 3 days to weeks after exposure

Will be allergic to penicillin derivatives and others in class

Sensitivity Test is indicated (ST to specific drug may give non-specific-positive reaction)

DO NOT use Primaxin (50% are positive to iminipram)

Aztreonam is OK (negligible reactivity)

Cephalosporins

10-15% of patients show cross allergy with penicillins (and vice-versa)

Sensitivity Test IS NOT indicated

Classification of Immune Reactions

Type I	IgE mast cell	Immediate à within minutes; show urticaria, and anaphylaxis (can be fatal) Accelerated à 1-72 hours; show urticaria
Type II	Cytotoxic antibody	Late reactions à >72 hours
Type III	Immune complex	Late reaction Serum sickness
Type IV	Cell mediated	Late reaction Contact Dermatitis
Idiopathic	All Late Reactions	Morbilliform rashes Interstitial nephritis Stevens-Johnson syndrome (shedding of skin)

Factors Influencing Risk of Type I Penicillin Reactions

Age	Most occur in 20-49 year olds
Previous Reaction to Penicillin	Increases Risk 1-2 month after a reaction à antibodies detectable in 80% of pts Declines to < 20% of pts by 10 years
Type of Previous Reaction	Related to chance of re-reaction: Anaphylaxis (15% chance) Urticaria (8%) Exanthema (2%) Other/Uncertain (0.5%) No Reaction (0.45%)
General Atopy	Atopy infers familial tendency of hypersensitivity Not a risk factor
Route	Parenteral >> Oral

Skin Reactions to Drugs

(table in class notes showed reactions per 1000 recipients, here they are in percent for the ones that were highlighted)

Amoxicillin	5.14%
Trimethoprim-sulfamethoxazole	3.38%
Ampicillin	3.32%
Cephalosporins	2.11%
Erythromycin	2.04%
Doxycycline	0.47%

Use of Antibiotics in Treating Infected Root Canals

Antibiotics cannot reach and eliminate microorganisms (no blood circulation within necrotic pulp)
Source of infection is unaffected by systemic antibiotic therapy
Used as adjuncts to impede spread of secondary infections
Never a substitute for drainage procedures or proper endodontic therapy
There are rare indications for antibiotic treatment for endodontic infections

acute periradicular abscess with fever (indicates systemic infection)
spreading infections with cellulites and diffuse swelling
prophylaxis for medically compromised patients undergoing routine endodontic procedures
replantation of avulsed teeth

Antibiotic of choice is amoxicillin, then clindamycin if resistant (i.e., anaerobic)

Treatment of Relevant Dental Conditions

Condition	Treatment
Ulcerative Gingivitis	Metronidazole (Flagyl) Anaerobic bactericidal
Dental Caries	“No topical or systemic strategies available” Topical vancomycin may have some effect
Apthous Ulcers	Treatment is symptomatic (palliative) Not bactericidal or bacteriostatic

Antibiotic Prophylaxis

The risk of septicemia in dental related instances is most commonly associated with streptococcal species

Orthopedic surgeons are most concerned with staphylococcal infections

The risk of adverse reactions to the antibiotic may be greater than acquiring endocarditis

A bacteriostatic antibiotic (clindamycin, tetracyclines) should not be used with bactericidal (penicillins, cephalosporins)

Prevention of Bacterial Endocarditis (BE)

Most BE cases are not attributable to an invasive procedure
Cardiac risk is stratified (high, moderate, negligible) based on outcome
Dental procedures that cause bacteremia need to be more clearly defined
Specific protocol for antibiotics in Mitral Valve Prolapse

With regurgitation à requires prophylaxis

Without regurgitation à no need for prophylaxis

Initial dose of 2000 mg amoxicillin, 1 hour prior is recommended (no follow up dose needed)
Erythromycin is no longer recommended for penicillin allergies à clindamycin as an alternative
Orthopedic surgeons are concerned with staphylococcus infections, while dentists are concerned with streptococcus infections

Endocarditis Risk Categories (American Heart Association)

High

(Primary Coverage)

Prosthetic cardiac valves
Previous bacterial endocarditis
Complex cyanotic congenital heart disease
(single ventricle states, transposition of great arteries, tetrology of Fallot)
Surgically constructed systemic pulmonary shunts/conduits

Moderate

(Optional Coverage)

Other congenital cardiac malformations
Acquired valvar dysfunction (rheumatic heart disease)
Hypertrophic cardiomyopathy (enlarged heart w/ disease)
Mitral Valve Prolapse with regurgitation

Negligible

Innocent Heart Murmurs (confirmed by echocardiogram)
Mitral Valve Prolapse without regurgitation
Congestive Heart Failure
Arrhythmias
Hypertension
Implanted Pacemaker
Joint Prosthesis (Hip, Knee)
Silicon Implants
Atrial-Coronary by-pass
Ocular lens implant
Vascular stent (resulting from angioplasty)

nRequires prophylaxis

Dental Procedures (American Heart Association)

Endocarditis Prophylaxis Recommended	Dental Extractions Periodontal Procedures (surgery, SRP, probing, SPT) Dental Implant Placement Reimplantation of Avulsed Teeth RCT Beyond Apex Subgingival Placement of Orthodontic Bands (but not brackets) Intraligamentary Local Anesthetic Injections Prophylactic Cleaning of Teeth w/ Bleeding
Endocarditis Prophylaxis Not Recommended	Restorative Dentistry with or without retraction cord Local Anesthetic Injections (nonintraligamentary) Intracanal RCT; Post Placement and Buildup Placement of Rubber Dams Postoperative Suture Removal Placement of removable pros/ortho appliances Taking of oral impressions Fluoride treatments Taking of oral radiographs Orthodontic appliance adjustment Shedding of primary teeth

Orthopedic Implants and Antibiotic Prophylaxis

Endocarditis Prophylaxis

Should Be Considered

In These Patients With

Total Joint Replacement

Immunocompromised
Radiation Induced Immunosuppression
Inflammatory Arthropathies
Rheumatoid Arthritis
Systemic Lupus Erythematosus (SLE)

History of Type 1 Diabetes Mellitus (appear to be more susceptible to infection)
Joint Replacement Within Past 2 Years
Previous Prosthetic Joint Infections
Malnourishment
Hemophilia

Endocarditis Prophylaxis

Not Indicated for

Dental Patients

With Pins, Plates, Screws
Most Replacements
Intravascular Stent

Combination of treatment should be planned within the same period of prophylaxis,

otherwise observe an interval of 9 to 14 days (â resistant organisms, á antibiotic flora)

What if a patient is unable to take oral medications for prophylaxis?

AHA provides guidelines, however, the general dentist is not qualified to make parenteral injections

à No Penicillin Allergy

ampicillin 2.0 g (adults) or 50 mg/kg (children) IM/IV 30 min. prior

àPenicillin Allergy

clindamycin 600 mg (adults) or 20 mg/kg (children) IM/IV 30 min. prior

cefazolin 1.0 g (adults) or 25 mg/kg (children) IM/IV 30 min. prior

(not for pts. with type I hypersensitivity)

What if a patient is currently taking an antibiotic (e.g. to prevent recurrent RF) that would normally be used for endocarditis prophylaxis?

à A very controversial area

à Dr. Levy suggests staying within the same class

à AHA suggests going outside of class rather than increase dose within class

Remember, a bacteriostatic antibiotic (clindamycin, tetracyclines) should not be used with a bactericidal (penicillins, cephalosporins)

What if a dental patient has a history of taking fen-phen?

à Patient should have, or obtain a current medical evaluation (echocardiogram)

à Some patients that have taken fen-phen have shown the development of cardiac valvular dysfunction

à Cardiac valvular dysfunction requires antibiotic prophylaxis

Is there a correlation between periodontal disease and increased coronary heart disease risk?

à A study by the AMA “did not find convincing evidence of causal association between periodontal disease and CHD risk”

What if a patient has suspected mitral valve prolapse and the presence of regurgitation is not known?

à IF no confirmation available AND immediate procedural need then provide prophylaxis

à IF regurgitation is confirmed then provide prophylaxis

à IF no regurgitation in confirmed then no prophylaxis is necessary

Bacterial Endocarditis and Antibiotic Prophylaxis Conclusions

Noncompliance with AHA guidelines is common
Poor oral hygiene is more often the cause of IE with oral origin than dental procedures

Patients at high risk for IE are encouraged to maintain a high level of oral health

Antibiotic regimens are not foolproof
Antibiotic regimen is not necessary for oral injections in the absence of bleeding-inducing procedures
Change of antibiotic suggested for patients currently taking antibiotics in need of prophylaxis
Risk of toxic effects from antibiotics is sometimes (in all but highest-incidence, highest-mortality IE group) a greater risk than endocarditis
Oral antibiotic regimens are recommended
Antibiotic prophylaxis only for patients with MVP and regurgitation

Macrolides

Agents	Erythromycin à prototype; introduced 1950 Clarithromycin (Biaxin) Azithromycin (Zithromax)
Half-Life	Biaxin à 4.3 hours Zithromax à 35-50 hours
Mechanism of Action	Bacteriostatic (similar to clindamycin, tetracyclines)
Spectrum	Narrow gram-positive
Bacterial Resistance	Moderate
Allergic Potential	Low (compared to penicillins)
Cross Reactivity	Very little
Special Problems	Potential for drug interactions Nausea, vomiting, abdominal pain à erythromycin

Erythromycin

Has different salt forms à each with its own GI side effects
Inhibits P-450 enzyme in the liver

á blood levels, á pharmacological effects, á toxic effects

Azithromycin

Sold as Zithromax
Packaged from pharmacy as Z-Pack (6 tablets @ $110)
7^th most frequently prescribed in 2002

Antibiotic/Food Interactions

It is recommended to take the following on an empty stomach

Ampicillin, cloxacillin, dicloxicillin, tetracyclines

For the others, it probably doesn’t matter

Dairy products limit the efficacy of tetracyclines (doxycycline), and fluoroquinolones

Form chelates with metallic ions like Ca²⁺, Mg²⁺, and iron salts

Fluorquinolones

Agents	Ciprofloxacin (Cipro)
Mechanism of Action	Bactericidal Different than others à inhibit DNA gyrase Good soft tissue penetration
Spectrum	Broad (gram-negative and gram-positive)
Bacterial Resistance	S. aureas shows resistance
Contraindications	Pregnancy Children under 18 Hypersensitivity to fluoroquinolones
Drug Interactions	Al, Mg, Ca, Fe taken concurrently (form chelates) May á blood levels of warfarin
Special Notes	Exposure to sunlight can cause rash (totally reversible) Not a first or second line antibiotic in dentistry Effective in sinusitis Avoid liquid dairy products â Antibiotic Plasma (70-92%) â Bioavailability (30-36%)

Antibiotic and Estrogen-containing Oral Contraceptives

Each of the following are shown to reduce the efficacy of OC

Penicillins	Pen V (â circulation of estrogens) Ampicillin, Amoxicillin
Cephalosporins	Cephalexin (â circulation of estrogens)
Tetracyclines	Tetracycline (â circulation of estrogens, á hepatic breakdown of estrogen)
Macrolides	Erythromycin (â circulation of estrogens, á hepatic breakdown of estrogen)
Anaerobic/Antiprotrosal	Metronidazole (â circulation of estrogens)
Antituberculosis	Rifampin (á liver metabolism of estrogen)
Clindamycin	Does not appear to interact with OC Does reduce GI microbial flora Still advise patients to use alternate methods

Always advise patients taking estrogen-containing oral contraceptives of potential antibiotic interference

Drug Regulations

Drug recalls occur due to being unsafe, ineffective, or non-economical

Controlled Substances are monitored by the DEA because of their potential for abuse

Controlled Substance Classification

Schedule I	Illegal Drugs High Abuse Potential No Therapeutic Use	Heroine
Schedule II	Medically Acceptable Use High Abuse Potential	Cocaine, Codeine, Morphine, Oxycodone
Schedule III	Medically Acceptable Use Less Abuse Potential than Class II	Vicodin
Schedule IV	Medically Acceptable Less Abuse Potential than Class III	Darvocet
Schedule V	Medically Acceptable Less Abuse Potential than Class IV

Triplicate Form required for Schedule II drugs

Application Fee is $210.00 for 3 years

DEA registration number is also enforced by Texas Department of Public Safety (DPS)

DEA registration number is required on a prescription for any controlled substance

Schedule II drugs à dispense within 7 days of date on Rx

Schedule V-III drugs à dispense within 6 months with a maximum of 5 refills

Drugs that are not controlled substances (e.g., amoxicillin) do not require the use of a DEA number

Tips for Prescribing Controlled Substances

Keep a minimum of blanks in a safe place
Write in ink, indelible pencil, or type Schedule II scripts
Write out amount
Avoid writing for large quantities
Maintain a minimal stock
Secure stock in a safe, locked place
Be aware of patients mentioning other prescriptions of controlled substances à check records
Use prescription blanks only for writing scripts
Never sign blanks in advance
Maintain accurate records
Be able to verify information for pharmacist
Contact DEA office when necessary (calls are in strictest confidence)

Prescription Writing

The three most common components of a prescription are the Superscription, Subscription, and Signa

Superscription

Inscription

Tells what is being prescribed

Includes dose (quantity of drug per dose form)

States dose form (physical entity ingested à tablet, capsule)

Describes simple vs. compound prescriptions

Subscription

Disp:

Tells how much of the drug to be dispensed

Write in numbers and letters for controlled substances

Signa

Sig:

Tells the patient what to do

Number of units per dose (one tablet, one teaspoon, etc.)

Route of administration (mouth, nasally, rectally, etc.)

Frequency of dosing (every six hours, once a day, etc.)

Duration of dosing (for seven days, until gone, etc.)

Purpose of prescription (goes on label)

Special instructions (shake well, refrigerate, etc.)

Other Components of a Prescription

Patient Information	Name, Address Age (required for triplicate form) Weight (important for Pediatric patients, obese patients as some meds are prescribed as mg/lb or mg/kg)
Date	Schedule II drugs à only dispensed within 7 days of Rx date All prescriptions expire after one year Schedule V-III à maximum of 5 refills over a 6 month period
Signature Lines	This makes the prescription a legal document Include degree Two signature lines required à dispense as written; substitution permitted
Prescriber Information	Name Address, Phone, DEA # printed or stamped (for controlled substances)
DEA Number	Number provided by DEA for prescribing controlled substances Also enforce by Texas Department of Public Safety (DPS) Required for prescribing any controlled substance
Refills	Indicate either no refills or the number allowed Proper use ensures the patient gets correct dose
Warnings	Labels for special precautions to patient: “Medication may discolor urine and/or feces” “Do Not Drink Alcoholic Beverages While Taking This Medication” “May Cause Drowsiness” ”Give Medication on Empty Stomach” “Do Not Take With Dairy Products”

Common Prescription Abbreviations

ā	Before	pc	After eating
ac	Before meals	po	By mouth
ad lib.	At pleasure	prn	As needed
aq, H2O	Water	qh	Each hour
bid	2 times a day	q4h	Every four hours
c	With	qid	4 times a day
cap	Capsule	Rx	“take thou”
d	Day	s, sine	without
disp	Dispense	sig	Write on the drug label
gtt	Drops	ss, ss	One half
h	Hour	stat	Immediately
hs, HS, hor som	At bedtime	tab	Tablet
no, #	Number or amount	tid	3 times a day
non rep, nr, NR	Do not repeat (or refill)	USP	United States Pharmac.

Be sure to write “Do Not Substitute” when the prescribed medication must/should be the name brand

Generic brands are usually equally effective, but often present with additional side effects

California (along with Hawaii and Kentucky) uses “Do Not Substitute”, other states may use slightly different terms

Dental Scope of Prescription Writing

Do not prescribe for patients who are not of record

Do not prescribe drugs for conditions unrelated to dentistry

Should not prescribe for family members or for self (for controlled substances is prohibited)

Be sure that patients are aware of all pertinent information regarding medication (don’t rely solely on pharmacist)

All prescription drugs must be properly labeled and packaged à including “samples”

It is permissible in California to dispense samples to patients

Many drugs are available precounted, prelabelled, and ready-to-dispense from certain Rx services

Be careful of potential forgery of prescriptions à vicodin is #1 forged prescription