pharma drug form

8/14/2019 Pharma Drug Form

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Drug Formulations

&Routes of

Administration

Ma. Minda Luz M. Manuguid, M.D.


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General Considerations

Pharmaceutics branch of Pharmacythat deals with drug formulations

Pharmaceutical products need to bepresented in a form that can beadministered to an organism

Formulation takes into considerationeasy delivery as well as guaranteeddesired action (drug reaches target,

achieves therapeutic action)


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Oral Preparations

Pill round or ovoid solid body; may be coatedwith sugar or other substance

Tablet granulated powder containing one ormore medications, compressed into a disc; mustdisintegrate in the GIT, so starch is oftenincorporated; + sugar-/film- coating;

Dragees chewable tablets

Enteric-coated tablets coated with asubstance that is stable at acidic pH (will not

disintegrate in the stomach) but breaks downrapidly at higher pH (small intestines)


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Oral Preparations

Capsule an outer shell holds the druginside

Hard gelatin capsule contains solid drug inpowder form; may be opened

Soft gelatin capsule contains the drug in liquid

or semi-liquid form; cannot be opened; usefulfor drugs that are insoluble in water

Sustained/Slow-release preparations drugis formulated in such a way that it releasesvery slowly in the GIT; a single dose suffices

for delivery of the drug over a period ofhours, ensuring sustained action.


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Oral Preparations

Liquid preparations for children & foradults who have difficulty swallowingpills; usually flavored to make thempalatable;

Elixirs drugs insoluble in water aredissolved in Alcohol

Syrups sugared liquid preparations

Suspension drug in solid form, not

dissolved in Alcohol Emulsion drug in liquid form, notdissolved in Alcohol


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Topical Preparations

Topical application of a drug to the skin/ mucosaoverlying the area to be treated

Drops isotonic solutions ophthalmic, nasal,otic (eardrops formulated as oily solutions foradherence to the aural cavity)

Creams water-based, poorly absorbed; drug isleft on skin surface as water evaporates

Ointments lipid-based, greasy appearance &feel; drug penetrates deeply into tissues,especially if with occlusive dressing

Pastes have a very high powder content;

water-repellent. Gels & Lotions used on hairy parts of the body.


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Topical Preparations

Intranasal sprays often metered todeliver precise doses of the drug; can beabsorbed systemically

Transdermal patches useful foradministering lipophilic drugs & thosethat are active in very small amounts

Suppositories useful in nauseous orvomiting patients, unconscious patients,patients with difficulty of swallowing;may be administered rectally orvaginally (Pessaries)


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Parenteral Preparations

Parenteral mode of drug administration thatavoids the GIT. Drug injections. Use of ASEPTICTECHNIQUE very very important!!

Intravenous (IV) injections fast action due toavoidance of GI absorption

Intradermal injected into the dermis; very

slow absorption; only small quantities of thedrug can be given this way.

Subcutaneous just beneath the skin; veryslow route; poor blood supply

Intramuscular into the fleshy part of themuscle: gluteus, deltoid, anterior thigh;


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Routes of Administration

Oral

Sublingual

Mucosal

Transdermal Rectal

Vaginal

Subcutaneous

Intramusclar

Intravenous

Intrathecal

Intra-articular

Epidural


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Routes of Administration

Oral

most convenient, most economical

rate & extent of absorption determines onset ofdrug action/effect

usual site of absorption: small intestines nonionized lipid-soluble forms favor absorption

weak acids are highly ionized in small intestinal alkaline pH

weak acids are readily absorbed in the stomach


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Oral administration

First pass effect: Drugs absorbed from the GIT passes through the portalvenous system, then through the liver before finallyreaching the systemic circulation, to the receptors &target tissues

Extensive hepatic metabolism/extraction results in

minimal drug delivery to the systemic circulation(e.g.propranolol,Demerol, INH)

poor liver extraction, bioavailability e.g. diazepam,warfarin

Disadvantages

emesis due to GIT irritation destruction of drug by gastric acid/ GI enzymes

unreliable or inconsistent absorption

metabolism of drug by intestinal flora


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Transdermal administration

Advantages

Sustained therapeutic plasma levels

Reliable drug absorption Molecular wt < 1000

pH range 5 9 in aqueous medium

No histamine-releasing action

Daily drug requirement < 10 mg

Smaller doses, so lower incidence of side

effects Generally good patient compliance

Examples: scopolamine, nitroglycerin,nicotine


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Rectal administration

Proximal rectum administration absorptioninto superior hemorrhoidal veins portalvenous system - liver - systemiccirculation

Low rectal administration entry into thesystemic circulation without passingthrough the liver

Generally unpredictable pharmacologicalresponses

Rectal mucosal irritation possible Examples: antipyretics, anticonvulsants


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Parenteral administration

Ensures active drug absorption More rapid drug delivery than Oral Only route acceptable for

unconscious patients, uncooperative

patients Systemic absorption depends on

capillary membrane surface area,drug solubility in interstitial fluid

Advantages: Rapid precise blood drug levels Irritant drugs more comfortably administered Drug is rapidly diluted


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Specialized Modes ofAdministration

Intrathecal drug is introduced into theCSF-filled space surrounding the spinalcord; for giving of drugs directly into theCNS, avoiding the blood-brain barrier

Epidural drug is introduced into thespace above the dura; useful inadministering local anesthetics forsurgical procedures in the pelvic area &below

Intra-articular injection directly intojoint spaces


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The Drug Order /Prescription

Contents of a Prescription:

name of medication

amount of medication to be given

(dose) route of administration

frequency of administration

other information: prescribingphysicians name, signature, licenseno., PTR no., S2 no. if applicable;date; patients name, age, etc.,


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frequency abbreviation

explanation

every day q. d. q. Lat. quisque =

everyd. Lat diem = day

every otherday

q. o. d. o - other

every hour

every 2 hrs

every 3 hrs.

etc.

q. h.

q. 2h.

q. 3h.

etc.

h hora = hour

2x a day

3x a day

4x a day

b. i. d.

t. i. d.

q. i. d.

b. bi = twice

t. tri = thrice

q. quad = four times

as much as q. s. q. quantity


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explanation

everymorning

q. a. m. q. every

a. ante = before

m. meridiem = noon

atbedtime

h. s. h. hora = hour

s. somni = sleep

beforemeals

a. c. a. ante

c. - cibum = meal

aftermeals

p. c. p. post = after

c. cibum = meal

as desired ad lib ad libitum = at ones

pleasure


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explanation

asnecessary

s. o. s. si opus sit = if it is

necessary

as needed p. r. n. pro re nata = asoccasion

requires

immediately

stat statim - immediately

with c cum = with

before a ante = before


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Drug Dosage units of measurement: units/hr.; mg./hr.;

mg./min.; mcg/min.; mcg/kg/min formula : dose = rate x concentration

nonparenteral meds capsules & unscored tablets are rounded to the nearest

whole tablet

Scored tablets are rounded to the nearest tablet Liquid meds are rounded to one decimal place (tenth)

parenteral meds Intradermal inj 0.1 ml. or less

Subcutaneous 1.0 ml or less

Intramuscular 1.0 ml or less for older infants & young

children; 2.0 ml or less for elderly thin adults & children; upto 3.0 ml in large muscles in well-developed adults


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Dosage calculations

Rate always in ml./hr.

Ratio & Proportion equationscontaining ratios of equal value

separated by colons or written asfractions. e.g. 2 : 6 = 4 : 12 thetwo inner numbers, 6 & 4, are themeans; the two outer numbers, 4& 12, are the extremes. Theproduct of the means must equalthe product of the extremes.


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Calculations

Intravenous calculations drop factor

macrodrop factor of 10, 15, or 20 drops per ml

microdrip 60 gtts/ml

Formula for calculating iv flow rate:

V1/T1 = V2/T2 where V1 volume to infuse;

T1 time to infuse;

V2 drop factor;

T2 - time in minutes


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Pediatric Calculations

Based on body surface area

BSA is determined from a normogram

Formula: childs BSA /1.7 sq. m. x adult dose

Based on body weight:

Convert childs weight to kg. (1 kg. = 2.2 lb)

Calculate the medication dose, then the daily dose, thendivide the daily dose by the number of doses/day


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