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Reading assignments: Katzung’s Basic & Clinical Pharmacology, 13th Edi,Ch-1,p10-19, Ch-2,p37-38 Ch-4,p69-71,Ch-66,p1119-1131, Ch-65,p1109-1117 ; Sanjib Das M.B.B.S.,M.D.,P.G.D.H.A. 1 Learning Objectives Determine the different factors modifying drug action Explain in detail about different processes involved in drug development Discuss pre-clinical (animal) studies and different phases of clinical trials Explain the concepts of investigational New drugs (IND) and New drug application (NDA) Describe different components of prescription writing Describe different components of prescription writing Demonstrate how to write a good prescription Explain the concepts of rational Prescribing Describe the selection of Personal (P-) Drugs Discuss the concepts of Essential Medicine Define terms associated with drug use behavior (Compliance, adherence and concordance) Recognize legal terms such as Comprehensive Drug Abuse Prevention and Control Act Identify different schedules of drugs Identify the US FDA teratogenic risk categories 2 Case Based Learning Julie Smith is a 35 year old female nurse working with isolation wards of a community hospital.She has been taking oral contraceptive pills since last couple of years .Recently couple of months ago she took some medication as prophylaxis after having an exposure to a meningococcal meningitis patient. On the next month she came to Gynaecology OPD with complaint of amenorrhea . Laboratory test shows a positive pregnancy test although she was still on contraception.. 1.Figure out the possible underlying cause of her contraception failure . 2.Discuss in details about various types of D-D Interactions that can take place both in Pharmacokinetic (absorption, plasma protein binding level, metabolism & elimination ) & pharmacodynamic (receptor level interactions) level with some examples 3 NBME Drug Interactions Pharmacokinetic mechanisms: Absorption: rate and extent of drug absorption may be altered; reduction in rate of absorption is not often clinically important; reduction in extent of absorption may result in subtherapeutic serum levels. Examples: Cholestyramine: resin binds with drugs and prevents absorption Antacids: metals chelate tetracyclines and fluoroquinolones preventing their absorption Anticholinergics (e.g., atropine): decrease gastrointestinal motility and slow absorption of many drugs Gastrointestinal motility alteration: may alter absorption; for example, delay absorption of some weak organic acids Drug Interactions NBME Pharmacokinetic mechanisms: Distribution: ○ Displacement of drugs from plasma protein binding sites Plasma Protein Binding: Oral hypoglycemic agents (e.g., tolbutamide); Oral anticoagulants (e.g., warfarin); Antimetabolites (e.g., methotrexate) ○ ○ Displacement of drugs from tissue binding sites (eg. digoxin displacement by quinidine) pH gradients: example, weak organic bases accumulate in milk which is acidic in comparison to blood Biotransformation: see inducers and inhibitors presented on earlier slides Drug Interactions Pharmacokinetic mechanisms: Excretion: ○ Alkalinization of urine (sodium bicarbonate) enhances excretion of weak organic acids ○ Acidification (ammonium chloride) of urine enhances the excretion of weak organic bases ○ Block tubular secretion (probenicid inhibition of penicillin secretion) NBME Drug Interactions NBME Pharmacodynamic mechanisms: Additive or synergistic effect is often observed when drugs with similar pharmacologic effects (e.g., Valium and ethanol) are administered concurrently Conversely, drugs with opposing pharmacological effects (propranolol and isoproterenol; naloxone and morphine) may reduce response to one or both drugs Combined toxicity: combined use of two or more drugs, each with toxic effects on a given organ Can enhance likelihood of organ damage Administration of two nephrotoxic drugs (aminoglycoside and vancomycin) can produce kidney damage even when dose of either agent alone may have been insufficient to produce toxicity Which of the following agents if taken concomitantly might reduce effectiveness of Tetracycline/FQs? (A)A calcium containing health tonic (B)An antihistamine (C)A nonsteroidal anti-inflammatory (D)An anxiolytic (E)A peg of whisky A jaundiced one-day-old premature infant with an elevated free bilirubin is seen in the premature-baby nursery. The mother received an antibiotic combination preparation containing sulfonamide for a urinary tract infection (UTI) one week before delivery. You suspect that the infant's findings are caused by the sulfonamide because of the following mechanism: (A)Enhanced synthesis of bilirubin (B)Competition between the sulfonamide and bilirubin for binding sites on albumin (C)Inhibition of bilirubin degradation (D)Inhibition of urinary excretion of bilirubin (E)None of the above A 35 years old female has ingested toxic amount of a drug which she was receiving in the treatment of her Headache. Routine Urine examination revealed significant lowering of urinary PH. Doctor prescribed Sodium Bicarbonate by parenteral route with a Pharmacotherapeutic concept that a. Sodium Bicarbonate being alkaline would neutralize acidic urine by its chemical action b. Sodium Bicarbonate would take care of metabolic acidosis c. Sodium Bicarbonate would hasten the excretion of ionized aspirin by creating an alkaline environment in the tubular fluid d. Sodium Bicarbonate is known for chelation of basic drugs e. Sodium carbonate reduces the threat for Acute Tubular Necrosis which might occur during acideurea. Which of the following best describes the use of celecoxib in the treatment of rheumatoid arthritis in a 55-year-old man with severe cardiovascular disease? A. B. C. D. E. Contraindicatory therapy Answer: A Lethal therapy Idiosyncratic therapy Cox-2 inhibitors are Life saving therapy contraindicated in patients with a history of cardiovascular disease; lack of production of Preferred therapy PGI2 to offset the actions of TXA2 Drug evaluation definitions Single-blind study A clinical trial in which the investigators-but not the subjects-know which subjects are receiving active drug and which are receiving placebos Double-blind study A clinical trial in which neither the subjects nor the investigators know which subjects are receiving placebos; the code is held by a third party IND Investigational New Drug Exemption; application for FDA approval to carry out new drug trials in humans; requires animal data NDA New Drug Application; FDA approval to market a new drug for ordinary medical clinical use Placebo An inactive "dummy" medication made up to resemble the active investigational formulation as much as possible Learning objectives Understand the process of drug development and evaluation Understand the clinical trial Be familiar with regulation processes Be familiar with informational systems available to practitioners. Drug evaluation definitions Phases I, II, and III of clinical trials Three parts of a clinical trial that are usually carried out before submitting an NDA to the FDA Positive control A known standard therapy, to be used along with placebo, to fully evaluate the safety and efficacy of a new drug in relation to the others available Mutagenic An effect on the inheritable characteristics of a cell or organism-a mutation in the DNA Teratogenic An effect on the development of an organism resulting in abnormal structure or function; not generally heritable Carcinogenic An effect of inducing malignant characteristics Drugs developed for diseases in which the expected number of patients is small. Some countries bestow certain Orphan drugs commercial advantages on companies that develop drugs for uncommon diseases FEDERAL REGULATIONS Safety and efficacy of drugs are regulated by the Food and Drug Administration (FDA) Animal Testing (see text for details) Acute toxicity: All drugs; single dose of the agent up to a lethal dose in 2 species (rodent; non-rodent) Subacute and chronic toxicity: Most drugs tested according to the least amount of time proposed for humans; i.e., 2-4 weeks (subacute) or 6-24 months (chronic), in at least 2 species Pharmacological profile Reproductive toxicity Carcinogenesis Notice of Claimed Investigational Exemption for a New Drug (IND) is filed with (FDA) once a potential drug is judged ready to administer to humans. The development and testing process required to bring a new drug to market in the USA. NBME Human Testing NBME Clinical trials are divided into four phases (see text for details): Phase 1: first time the agent has been administered to humans ○ First dose is always a placebo ○ Patient's anxiety may produce psychic or physiologic changes, placebo will keep investigator from confusing these artifacts with drug actions ○ Goal is to find maximum tolerated dose ○ Testing is never double-blind and usually involves 20-30 patients ○ No clear cut-off between Phase 1 and Phase 2 Phase 2: first attempt to determine clinical effectiveness of test agent; tests may be single-blind or double-blind and involve hundreds of patients Phase 3: extensive testing of a drug's efficacy and toxicity ○ Undertaken only if data from Phase 2 are positive ○ Phases 1 and 2 studies are usually conducted by clinical scientists, but phase 3 may include physicians in private practice ○ After completion, company files New Drug Application (NDA) with FDA ○ Fewer than 10,000 subjects are usually tested before Phase 4. Phase 4 (post-marketing surveillance): adverse effects and toxicity become most evident (incidence of aplastic anemia in chloramphenicol therapy is 1/40,000) •In which phase patients of the testing drug is typically included in the study (A)Lab testing (B)Animal testing (C)Phase I (D)Phase II (E)Phase III Informed Consent Required for Phase 1, 2, and 3 subjects Must be in writing for Phase 1 and 2 Peer review (Committee on Human Experimentation) protects the interest of subjects, investigators, & institutions Orphan Drugs In the USA, current legislation provides for tax relief and other incentives designed to encourage the development of orphan drugs. Objectives Define a prescription and the classification of medications Compare and contrast the various schedules of controlled substances Compare and contrast a prescription medicine and a non-prescription medicine List the component elements of the prescription Objectives cont’d List the component elements of a controlled substance prescription Classify controlled drugs by their schedule Describe writing conventions associated with prescription writing Provide examples of “look alike,” “sound alike” prescription medicines, including trade names Objectives cont’d Provide examples of confusing abbreviations used in prescription writing Describe important prescription writing precautions for traditional and controlled substance prescriptions Define the “off label” use of a drug Prescription Order Writing Definition: A prescription is a written, verbal, or electronic order from a prescriber (e.g., physician, dentist, podiatrist, nurse practitioner) to a pharmacist for a particular medication for a specific medication at a certain time. Classification of Medications Prescription= “legend” drug or medication Prescription product label reads: “Caution: Federal Law Prohibits Dispensing without a Prescription.” Types of Prescriptions Generic The nonproprietary name provided by the United States Adopted Name (USAN) Council syn. Chemical Name e.g., amoxicillin, fluoxetine, diazepam, aspirin Brand Name The proprietary name or registered trademark name provided by the pioneer (innovator) pharmaceutical company who holds the patent on the drug e.g., Prozac®, Viagra®, Xanax® Types of Prescriptions cont’d Compounded Requires the preparation of one or more active ingredients with one or more pharmaceutical necessities, e.g., suspending agent, flavoring agent, to create a finished product. For example, an oral compounded prescriptions may be used to facilitate the administration of a solid dosage form that is not available in liquid form for patients unable to swallow a solid dosage form. ○ e.g., pediatric, geriatric Types of Prescriptions cont’d Control Substance Distribution of certain medicines with abuse potential is controlled through the Comprehensive Drug Abuse Prevention and Control Act of 1970 This Act is regulated and enforced by the federal Drug Enforcement Agency (DEA) MDs must be registered with the DEA to prescribe those drugs under the control of this act. Re-registration is mandatory every three years. *A partial listing of controlled substances is demonstrated in Appendix A. Further examples of drugs by schedule are found at http://www.dea.gov/pubs/scheduling.html Types of Prescriptions cont’d New An original prescription order dispensed for the first time. Refill A repeat dispensing of the original prescription order. Usually, encompasses patients on maintenance therapy, e.g., digoxin, phenytoin, lovastatin, potassium chloride. Schedules of Controlled Substances Schedule I No medical use with a high abuse and dependence potential A physician cannot write for this schedule of drugs e.g., LSD, Marijuana*, Heroin, Mescaline (Peyote), 1-(1- Phenylcyclohexyl)pyrrolidine (i.e., PCP). *Twelve states have laws regulating the medical use of marijuana- AL, AZ, CA, CO, HI, ME, MD, MT, NV, OR, VT, WA Schedules of Controlled Substances Schedule II A written prescription is required for this schedule. However, there are no refills allowable. Only in an emergency situation is an oral order allowable and acceptable to the dispenser. Must be followed by a written prescription within 72 hours. In some states (formerly IL), the physician must complete a triplicate prescription form to prescribe Class II in ink. The physician should write out the actual amount prescribed besides giving an Arabic Number or Roman Numeral for the quantity. This discourages forging or “alteration” of the prescription. In Illinois, a written prescription for this schedule must be dispensed within 90 days, i.e., 3 months, of issuance or it expires. e.g., amphetamines, meperdine HCl, cocaine, secobarbital sodium Multiple Prescriptions for Schedule II Controlled Substances DEA Rule 12/19/07 – Approved federal legislation to allow prescriber to write >1 prescription (not more than a 90 day supply total) for CII controlled substances in certain circumstances. ▪ Legitimate medical purpose. ▪ Instruction on each prescription indicating earliest date to dispense the prescription. ▪ This situation does not create an undue risk of diversion or abuse. ▪ Applicable state laws permit this practice including Illinois. ▪ Prescriber is in compliance with all other state and federal laws. Schedules of Controlled Substances Schedule III Drugs in this schedule have a moderate abuse and dependence potential May be prescribed in writing or through a verbal order. May be refilled up to five times within a six month interval from the date of issuance. e.g., glutethimide, chlorphentermine, phenmetrazine, anabolic steroids Schedules of Controlled Substances Schedule IV Drugs in this schedule are considered to have low abuse and low dependency potential May be prescribed through writing and through a verbal order. May be refilled upto five times within a six month interval from the date of issuance. E.g., alprazolam (Xanax®), pentazocine (Talwin®), flurazepam (Dalmane®) Schedules of Controlled Substances Schedule V Drugs in this schedule have the least amount of abuse potential and an unlikely dependency Consists primarily of medications that contain limited quantities of certain narcotic and stimulant drugs generally used as antitussives, antidiarrheals, and analgesics Can be purchased OTC by the patient who signs a registry e.g., Robitussin AC, Parepectolin, Kaopectolin PG Nonprescription Medications Can be purchased at pharmacies and retail outlets without a prescription (syn. Over-the-counter [OTC] products) To date, 99 drugs and/or drug dosage forms have been “switched” from prescription to OTC status (Note Appendix AA) Besides South Africa, the US is the only country NOT to have a “third class” of drugs. That is, available through the pharmacist. FL has a “pharmacist only” class of medications BTC being considered by FDA National Coordinating Council for Medication Error Reporting and Prevention (NCC-MERP) -- Founding Members American Association of Retired Persons; American Health Care Association; American Hospital Association; AMA; American Nurses Association; American Pharmacists Association; American Society of Health-System Pharmacists; FDA; GPIA; JCAHO; National Association of Boards of Pharmacy; National Council of State Boards of Nursing, Inc; PhRMA; United States Pharmacopeia NCC-MERP Recommendations to Improve Error-Prone Aspects of Prescription Writing All prescriptions must be legible. Prescribers should move to a direct, computerized, order entry system. Handwriting examples: Can you read this? Component Elements of the Prescription Heading Physician’s name, practice address and telephone number, DEA number Date prescription is written Patient Information Name, address, age (esp., if for a pediatric or geriatric patient) Component Elements of the Prescription Body of the Prescription (Note: Exhibit) RX Take Thou. Name of the prescribed drug or drug product. Also included is the strength of the medication, the number or quantity of the prescribed drug in addition to the dosage form ○ DO NOT use abbreviations for drugs prescribed unless the abbreviation is official, e.g., SSKI (Saturated Solution of Potassium Iodide), NSS (Normal Saline Solution), HCTZ (Hydrochlorothiazide), NTG (Nitroglycerin), MTX (Methotrexate) ○ Avoid “unofficial” abbreviations Component Elements of the Prescription - Body of the Prescription (cont’d) Sig Signatura (i.e., Mark Thou). Directions for use, e.g., one cap every 8 hrs. Avoid “ut dictum” or “as directed.” Units should be spelled out rather than writing “U.” Latin abbreviations (Appendix B) are acceptable as well as plain English Commonly confused Latin abbreviations include: qd, qod Refills “N” times or NR. Leaving this section blank implies that the prescription is non- refillable. Dangerous Abbreviations Abbreviation U µg Q.D. Q.O.D. MS, MSO4, MgSO4 Intended Meaning Units Micrograms Every day Every other day Morphine sulfate or magnesium sulfate? More Dangerous Abbreviations SC or SQ TIW D/C discontinue HS bedtime? cc AU, AS, AD I.U. Subcutaneous Three times a week Discharge; Half strength; Cubic centimeters Both ears, left ear, right ear International units Component Elements of the Prescription - Body of the Prescription (cont’d) Generic Authorization Physician signature on the “dispense as written” or “may substitute” line “No Child Resistant Packaging” Authorization All legend drugs intended for oral use must be dispensed by the pharmacist to the patient in containers having safety closures unless the prescribing physician or the patient specifically requests otherwise. A request for a non-child resistant container may be applied to a single prescription or to all of the patient’s dispensed medications. The pharmacist should clarify the patient’s desires, obtain and file a signed waiver request, and maintain the information in the prescription computer for future reference. Exception: Nitroglycerin (NTG) containing products. Component Elements of the Prescription - Body of the Prescription (cont’d) Signature Legible in indelible pencil or pen. Signature selections: May substitute_______________________ Dispense as written___________________ • DEA Number If necessary and, usually, within the heading of the prescription blank along with the physician’s practice information Writing Conventions For compounded prescriptions, when units are not given, solids are assumed to be in grams (g) and liquids in milliliters (ml). Never write a decimal without a zero preceding it, e.g., 0.15 g Clindamycin HCl. This helps to minimize an error in translation Never write a decimal with a zero following it, e.g., Propylene Glycol 6.0, Propylene Glycol 6 e.g., Rx Clindamycin HCl 0.15 Propylene Glycol 6 Lavacol qsad 30 Sig: Apply to affected area twice daily Writing Conventions (cont’d) Sometimes a vertical line is used for the decimal point, although, conceivably, it could be confused as a number one. ____ ○ e.g., Rx Chlorpheniramine Aspirin Dispense Caps #12 Sig: 0 l 002 0 l 325 One capsule po four times daily for allergy and pain Writing Conventions (cont’d) Liquid household measures Milliliter = ml 1 teaspoonful = 5 ml 1 tablespoonful = 15 ml 2 tablespoonfuls = 30 ml (approximately one ounce) 8 fluid ounces ~ 240 ml One pint = 16 fluid ounces = 473 ml One quart = 32 fluid ounces = 946 ml One gallon = 4 quarts = 8 pints = 3750 ml gtts = drops (e.g., oral, ophthalmic, ear, topical) Writing Conventions (cont’d) Solid weights mcg mg g gr = = = = microgram milligram gram grain (old apothecary system reserved for “older,” traditional medications). Note for these one grain is equal to 60 mg. Otherwise, one grain = 64.8 mg. ○ e.g., nitroglycerin, 1/150 gr, 1/200 gr, 1/400 gr; phenobarbital, ¼ gr., ½ gr.,1 gr.; thyroid ¼ gr, ½ gr, 1 gr. Writing Conventions (cont’d) Be very cautious about drug names that “sound/look” alike (Appendix C). http://www.nacds.org/wmspage.cfm?parm1=1915 Avoid using “unofficial” abbreviations for drugs/drug product names, e.g., PCN (Penicillin), SMX-TMP (Sulfamethoxazole-Trimethoprim), TCN (Tetracycline), KCl (Potassium Chloride), MOM (Milk of Magnesia). If confused, contact the pharmacist. Prescription Writing Suggestions Intended to ensure patient safety and minimize pharmacist intervention on behalf of the prescriber and the patient. Keep all prescription blanks in a safe place out of patient reach. This avoids the temptation and disappearance of blanks. Further, this procedure minimizes the number of prescription pads in use. Use a separate prescription blank for each prescribed medication. Prescription Writing Suggestions Ensure that refill directions are included on every prescription. Is it refillable or not? If refillable, indicate the number of times or the duration of time that refills are authorized. It will save the prescriber time and interruptions in the long run. Legally, aside from refill limitations associated with controlled substances, a prescription refill for a conventional, non-controlled medication has a one year expiration time. Prescription Writing Suggestions Attempt to make the prescription order alteration proof. Use indelible pencil or ink and for controlled substances write the number and spell it out. Otherwise, for example, a “XII” can be forged to read “XXX.” Use the same pen or indelible pencil for the entire prescription. If a mistake is made, e.g., number of tablets, cross out the mistake, write/print “error” above it, and then initial it. Prescription Writing Suggestions Avoid writing a prescription for a large quantity of drug unless it is absolutely determined that such a quantity is necessary. For an anticipated chronic medication, it is better to start with a lower number at first in the event that the patient cannot tolerate it because of side effects. Think also of the economic considerations. Insurance plans will limit the amount to one to three months at most. When an institutional prescription blank is used, the prescriber should clearly print his/her name, address, DEA registration number on the blank. Prescription Writing Suggestions for Controlled Substances Again, this is intended to ensure patient safety and minimize pharmacist intervention on behalf of the prescriber and the patient. Use a separate prescription blank for each substance prescribed. Maintain only a minimum stock of controlled substances in the medical bag, and it should be taken by the physician while away from the automobile. Keeping the medical bag locked in the automobile trunk is not always an effective deterrent. Prescription Writing Suggestions for Controlled Substances During the drug history, if a patient concedes that he/she has received a controlled substance prescription from another physician, consult that physician or the hospital records, and/or examine the patient to decide if a controlled substance should be prescribed. Do not allow the patient to dictate the controlled substance, if any, to be prescribed. The patient may be “doctor shopping.” Maintain an accurate record of controlled substance products dispensed as required by the Controlled Substances Act. Prescription Writing Suggestions for Controlled Substances A prescription order blank should only be used for writing the prescription. Do not use it to write a note and/or information for the patient. An unscrupulous drug dealer or abuser could erase the information easily and use the blank to forge a prescription drug. Prescription Writing Suggestions for Controlled Substances The prescriber should use the pharmacist as a valuable resource when needed. Also, assist the pharmacist when he/she inquires to verify information about a prescription order. A corresponding responsibility/liability rests with the pharmacist who dispenses the prescription order. Telephone the nearest DEA field office to secure and/or furnish information. The call is held in strictest confidence. Unlabeled (syn Off-Label) Use (Indication) Serendipitous observations (e.g., decreased migraine headache attacks while maintained on β-blockers for cardiovascular therapy; sildenafil citrate clinically evaluated for lowering blood pressure demonstrating use for erectile dysfunction) and therapeutic interventions of physicians have led to medicines being prescribed for unlabeled use for which the drug has not been approved by the FDA. The off-label use is supposed to be based upon a rational scientific theory, expert medical opinion, or evidence based on sound clinical trial(s). Unlabeled (syn Off-Label) Use Commonly used for depression, cancer, HIV/AIDS, dermatological disorders, and migraine . Common in the pediatric population—danger ↑ AEs. In 2001, ~73% off label prescriptions were not supported by scientific evidence. Unlabeled (syn Off-Label) Use (Indication) The FDA makes clear that it neither has, nor desires, the authority to compel physicians to adhere to only “official” labeled indications. Simply, experience has demonstrated that the official indications “lag” behind scientific knowledge and the scientific/medical literature. Unlabeled (syn Off-Label) Use (Indication) A Supplemental New Drug Application (NDA) may be filed by the drug manufacturer when approval is sought for an additional indication for a drug already approved for another indication. It has been estimated that 40% of all prescriptions are written for indications for which a Supplemental NDA has not been filed. While this process is less demanding, drug manufacturers do not want to invest the time, energy, and $$ to do so. Consequently, this has resulted in 75 to 90% off-label prescribing for infants and children. The caveat is less than desirable dosing and warnings for the pediatric patient with increased incidence of adverse effects. Single Patient Compassionate Use A FDA-requested mechanism for a physician to use a drug in a single patient, usually in a desperate situation when there is no response to other therapies or in which there is no approved or recognized treatment available. Single Patient Compassionate Use Approval for a compassionate use may be sought in the following situations when a(n): IND is in effect, but the drug is still in the early stages of testing. IND is in effect, but the intent of the drug use is not for the purpose described in the IND. drug has an IND, but it is not marketed. drug has had previous FDA approval but has been withdrawn from the market because of questions regarding its safety. drug is being investigated or marketed outside of the US, but no IND is in effect within the US. Often, the FDA will permit the proposed use under a commercial sponsor’s IND or under a new IND filed by the physician in behalf of an identified patient. References Scott SA. “The Prescription,” in Remington: The Science and Practice of Pharmacy, 21st Edition, A. Gennaro, Chairman, Editorial Board and Editor, Lippincott Williams and Wilkins, Baltimore MD, 2005, pp. 1823-1839. http://www.dea.gov/pubs/scheduling.html http://www.nacds.org/wmspage.cfm?par m1=1915 Updated: March 24, 2010