Pharmacology in midwifery Flashcards
What are the 4 main principles of quality use of medicines?
- judiciousness
- appropriateness
- safety
- effectiveness
Which regulatory body is respinsable for the regulation of medicines in Australia?
The therapeutic drugs administration (TGA)
What is a teratogen?
any substance that interferes with normal fetal development causing one or more developmental abnormalities
What is a mutagen?
a chemical or physical agent that causes a genetic mutation or increases the mutation rate
What is a carcinogen?
any agent that causes the development of cancer or increases its incidence
What is the role of the midwife in terms of pharmacology?
- education regarding indication, adverse effects, transfer to baby and safety in pregnancy/breastfeeding
- assistance in informed decision making
- appropriate administration
- assessing adverse drug effects
- interpreting and following standing orders
- working within local prescribing frameworks
What are the main antibiotics listed on the PBS for midwife prescribing?
- amoxycillin
- amoxycillin & clavulanic acid
- benzylpenicillin
- cephalexin
- clindamycin
- dicloxacillin
- flucloxacillin
- lincomycin
- nitrofurantoin
What is the name of the 2 eyedrops/eardrops listed on the PBS for midwife prescribing?
- chloramphenicol
- framycetin sulfate
What are the main anti-inflammatories that are listed on the PBS for midwife prescribing?
- diclofenac
- ibuprofen
What contraceptives are listed on the PBS for midwife prescribing?
- etonogestrel implant
- levonorgestrel
What is the main anti-emetic listed on the PBS for midwife prescribing?
- Metochlopramide
What opiod analgesic is listed on the PBS for midwife prescribing?
- morphine
What antacid is listed on the PBS for midwife prescribing?
- ranitidine
What are the main indications for giving antibiotics in the perinatal period?
- urinary tract infection
- GBS prophylaxis
- perineal infection
- caesarean wound infection
- endometritis
- neonatal skin infection
- mastitis
What is the usual indication for giving metochlopramide in the perinatal period?
relief of nausea and vomiting (particularly intrapartum)
What is the main anticonvulsant given in the perinatal period (particularly for preeclampsia)?
magnesium sulfate
What is the antidote to magnesium sulphate?
calcium gluconate
What are the 2 antidotes to metochlopramide?
- diphenhydramine
- benztropine
What are the 2 main antifungals that are usually given to treat vulvovaginal, nipple or neonatal oral thrush?
- iotrimazole
- nystatin
What is the generic name for the antiviral used to manage herpes simplex virus in late pregnancy?
Acyclovir
Which benzodiazepine is often given for rest and relaxation in early non-active labour?
Temazepam
Which 2 drugs act as dopamine-agonists and may be given to stimulate lactation postnatally?
- domperidone
- metochlopramide
What are the 2 key corticosteroids that may be given antenatally where there is threatened preterm labour?
- betamethosone
- dexamethasone
What is the immunoglobulin that is usually recommended to Rhesus (D) negative women with suspected rhesus positive pregnancies?
Human anti-D IgG
What is the antagonist given to women or infants to reverse the action of opiods in labour?
naloxone hydrochloride
What are the 2 most common NSAIDs given for postpartum analgesia?
- Diclofenac sodium
- Indomethacin
What prostaglandin may be indicated for management of PPH?
misoprostol
What drug may be used to manage anaphylaxis?
adrenaline hydrochloride
What antihypertensive is also used as a tocolytic?
Nifedipine
What are the main uterotonics given in the perinatal period? and what are their trade names?
- oxytocin (syntocinon)
- oxytocin/ergometrine (syntometrine)
- ergometrine maleate (ergometrine)
What are the main vaccines that may be indicated antenatally or postnatally?
- influenza vaccine
- Hep B vaccine
- MMR vaccine
What is the generic and trade name for drug given for prophylaxis of neonatal vitamin k deficiency bleeding?
- Phytomenadione (Vitamin K)
- Konakion
What are the three main schedule 8 medicines given for intrapartum or postnatal pain?
- pethidine
- morphine
- fentanyl
What are the 2 main intravenous fluids given in the perinatal period?
- 0.9% sodium chloride (normal saline)
- Compound sodium lactate/Hartmann’s solution
What are the 4 main indications for giving IV fluids in the perinatal period?
- retain patency of IV line
- administration of medication
- rehydration in labour
- fluid replacement (particularly in PPH)
What is the definition of the term chemical drug name?
the unique precise description of the drugs chemical composition and molecular structure
What is the definition of the term generic drug name?
- the official drug name as suggested by the manufacturer and approved by the regulating authority
- shorter and more memorable than the chemical name
- usually has a lowercase letter at the start (whereas trade is usually capitalized)
What is the definition of the term trade drug name?
- the proprietary or brand name that a drug is advertised under
What is the definition of the therapeutic action of a drug?
therapeutic effect is the desirable or beneficial effect of a medical treatment
Describe the process of drug absorption for oral medications
orally administered drugs must undergo disintergration, and dissolution prior to crossing mucosal and epithelial layers of the GI tract to find their way into systemic circulation
What is passive diffusion?
the transfer of a drug from an area of high concentration to an area of low concentration
What is carrier-mediated transport?
- movement across a membrane that requires the involvement of a membrane protein
- may be active (requiring energy) or facilitated
What variables influence how a drug is absorbed?
- nature of the absorbing surface (number of membrane layers, surface area, blood supply)
- chemical structure of the drug (lipid solubility, charge, molecular weight, dissolution rate, pH)
What normal physiological changes in pregnancy may alter drug absorption?
- delayed gastric emptying (twice as long in stomach) and decreased GI motility (increased small intestine absorption), possibly due to progesterone causing decreased smooth muscle contraction
- less acidic stomach (degree of ionisation)
- nausea/vomiting (unpredictable oral absorption)
- increased pulmonary absorption (increased tidal volume, alveolar ventilation, generally increased uptake)
- increased cutaneous absorption (increased cardiac output, increased cutaneous perfusion
What is the implication of the stomach environment being less acidic in pregnancy on absorption of drugs?
- drug must be uncharged (unionised) to cross membrane
- more weak acids unionised in acid environment, more weak bases unionised in basic environment
- less acidic environment means absorption of acidic drugs reduces and basic drugs increases
What is meant by plasma protein binding?
What is meant by adipose tissue binding?
- proportion of drug bound to proteins in circulation, only non-bound drugs exert pharmacological effects
- lipid soluble drugs tend to accumulate in fatty tissue
What is the hepatic first pass effect?
the variable proportion of an orally administered drug that is metabolised by the liver before exerting an effect
What is the sublingual route for drug administration?
What are benefits of sublingual administration?
drug placed under tongue to dissolve in saliva, person advised to refrain from swallowing, drug diffuses through mucosal membranes and enters circulation directly
- no hepatic first pass effect
- rapid absorption
note: drug must dissolve rapidly in saliva, be unionised with high lipid solubility
What is the buccal route for drug administration?
drug is placed between the teeth and the cheek
How are drugs metabolised?
- drugs undergo enzymatic modification (usually by liver enzymes) to convert them from lipid soluble to water soluble so that they may be eliminated from circulation
What is drug distribution and what are the main factors that impact it?
- the movement of drug around the body via circulation
- degree of distribution depends on concentration of free drug vs. bound drug, concentration of plasma proteins, body fat/water percentage, barriers to distribution
What are the two key barriers to distribution in the pregnant human body?
- blood brain barrier
- placenta
What is the role of the blood-brain barrier in drug distribution?
- selectively permeable filter made of endothelial cells covered in fatty glial cells
- has tight intracellular junctions and regulates movement of substances between blood circulation and brain and CSF
- only small, highly lipid soluble, non-charged ions tend to cross
What is the role of the placental barrier in drug distribution?
- fetomaternal circulation not fully developed during first 10 weeks
- placental barrier is membrane that separates maternal and fetal circulation
- most drugs cross placental barrier, increased distribution of drugs to fetus due to physiological changes in late pregnancy
- placenta plays minor role in drug metabolism
Define bioavailability
variable proportion of administered dose that reaches systemic circulation intact
Define pharmacokinetics
the absorption, distribution, metabolism and excretion of drugs
What is it vital for the midwife to understand drug pharmacokinetics?
- vital for midwife to understand normal pharmacokinetics and changes in pregnancy to safely prescribe and administer drugs and understand how drugs transfer through the placenta
What is a loading dose and why may it be administered?
a larger than normal dose given initially to rapidly achieve a therapeutic level of plasma concentration prior to maintaining with smaller doses up to module 1 drug dosages
Why is giving the correct dose of a drug vital?
- achieve maximum therapeutic effect
- avoid adverse effects and toxicity
What factors influence plasma drug concentration?
- absorption (particularly due to route of administration)
- distribution
- elimination
What is the half-life of a drug?
the amount of time taken for the blood plasma concentration to fall by one half
- drugs are usually administered every half life
- useful when considering use of drugs in breastfeeding women
What are the routes of drug administration?
- oral
- subcutaneous
- intramuscular
- intravenous
- intrathecal (spinal) and epidural
- inhalation
- topical
- rectal
What are the advantages and disadvantages of oral administration?
- safe
- convenient
- easy to self-administer
- variable absorption depending on factors like recent meals
- hepatic first pass effect
What is the subcutaneous route and what are the advantages and disadvantages of subcutaneous administration?
- injection into the connective tissue and fat immediately below the skin
- only appropriate for non irritating drugs
- slower absorption but more sustained effect
- no hepatic first pass
What is the intramuscular route and what are the advantages and disadvantages of IM administration?
- injection into muscle tissue
- higher blood flow than fat so more rapid absorption
- absorption variable depending on body fat and muscle
- not all drugs appropriate
- no hepatic first pass
What is the intravenus route and what are the advantages and disadvantages of IV administration?
- injected directly into circulation
- immediate effect
- irreversible
- requires more controlled administration (bolus or infusion)
- no hepatic first pass
What is the inhalation route what are the advantages and disadvantages of IV administration?
- drug administered by breathing a gas or fine mist into lungs
- large surface area for absorption, thin alveolar membrane and rich blood supply
- no hepatic first pass
- local or systemic effect
What kinds of topical administration are there?
- cutaneous (ointments or patches)
- nasal sprays
- eyedrops
What factors may influence topical, subcutaneous or intramuscular absorption of drugs?
- anything that increases perfusion
- massaging
- warming skin
What normal physiological changes in pregnancy may alter drug distribution?
- 30-50% higher blood volume
- 25% increase body fat
- lower concentration of plasma proteins in late pregnancy - more free drug
What normal physiological changes in pregnancy may alter drug metabolism?
- unpredictable and drug dependent
- fluctuations in liver enzymes
- placenta has limited contribution to metabolism
What normal physiological changes in pregnancy may alter drug excretion?
- 50-80% increased renal blood flow and GFR - increased renal excretion, particularly of water-soluble drugs
- decreased gastric motility so decreased fecal elimination rate
Define pharmacodynamics
What the drug does to the body - therapeutic and adverse effects, drug mechanism
What is anaphylaxis?
- a severe life-threatening systemic hypersensitivity reaction
- usually involve sudden onset and rapid progression
- airway/breathing/circulation problems
- skin and/or mucosal changes such as flushing, angioedema (hives) and urticaria
- gastrointestinal symptoms such as vomiting, abdominal pain, incontinence
What management may be required for anaphylaxis?
look for:
- Airway (swelling, hoarseness, stridor)
- Breathing (tachypnoea, wheezing, cyanosis, SpO2
What is an agonist?
mimic the effect of the endogenous ligand by binding and activating receptor
What is an antagonist?
antagonists bind to receptors but don’t activate, blocking the effect of the endogenous ligand
What is the sympathetic nervous system?
The sympathetic nervous system is responsible for fight or flight reactions e.g. increased HR, decreased gastric motility, contraction of sphincters and ejaculation
What is the parasympathetic nervous system?
The parasympathetic nervous system is responsible for rest and digest functions e.g. decreased HR, increased gastric motility, secretion of stomach juices, micturation
What factors influence drug transfer across the placenta?
- concentration gradient
- increased blood volume
- lipid solubility
- degree of ionisation
- molecular weight
Why is transfer of drugs to the infant higher in late pregnancy?
- increased unbound drug
- increased uteroplacental blood flow
- increased placental surface area
- thinner capillary membranes
What are important considerations when considering drug treatments in pregnancy?
- are there non-pharmacological alternatives that may be effective?
- what are the harms and benefits of prescribing or NOT prescribing?
- consider discussing the incidence of non-drug related congenital abnormalities (minor 15%, significant 2-4%)
- education and communication (informed consent, documentation, antenatal screening)
- dosage
What is Category A with regard to medicine use in pregnancy? What are two examples?
Category A - have been taken by a large number of pregnant women without proven increases in frequency of malformations or harmful effects on developing fetus
Remember paracetamol and salbutamol
other examples adrenaline, amoxycillin, ampicillin, antacids, bromocriptine, benzylpenicillin, betamethasone, bupivacaine, cephalexin, clindamycin, clotrimazole, codeine, dexamethasone, diphenhydramine, ephedrine, ethambutol, folic acid, hydrocortisone, insulin, lignocaine, lincomycin, methyldopa, metochlopramide, miconazole, nitrous oxide, nystatin, prednisolone, terbutaline, thyroxine
What is Category B with regard to medicine use in pregnancy? What are two examples?
Category B (1/2/3) - have been taken by a limited amount of pregnant women without an observed increase in fetal malformation or harmful effects, number indicates adverse effects on fetus in animal studies
Remember ondansetron and pseudoephedrine hydrochloride
other examples acyclovir, apomorphine, azithromycin, benztropine, cabergoline, cephazolin, chlomiphene, dexamphetamine, dicloxacillin, disulfuram, domperidone, etonogestrel, flucloxacillin, glyceryl trinitrate, hepatitis A vaccine, hepatitis B vaccine, HPV vaccine, ketamine, levonorgestrel, melatonin, metronidazole, naloxone, ranitidine, ropivacaine, rosiglitazone, terbinafine, ursodeoxycholic acid, vancomycin
What is Category C with regard to medicine use in pregnancy? What are two examples?
Category C - drugs which have caused or may be suspected of causing harmful effects (which may be reversible) without causing malformations
Remember aspirin and sertraline
other examples some benzodiazepines (diazepam, temazepam), SSRIs (citalopram, escitalopram, fluoxetine, sertraline), heparins (heparin, dalteparin, enoxaparin), NSAIDs (diclofenac, ibuprofen, indomethacin, parecoxib), beta-blockers (labetalol, metoprolol, oxeprenalol, propranolol), opioids (morphine, oxycodone, pethidine, tramadol), carbimazole, hydralazine, metformin, methadone, nifedipine
What is Category D with regard to medicine use in pregnancy? What are two examples?
Category D - drugs which may cause fetal malformations or irreversible damage
Remember lithium and warfarin
e.g. statins (atorvastatin, fluvastatin), ACE inhibitors (captopril, enalalopril, fosinopril), carbamazepine, fluconazole, gentamicin (used for severe sepsis), methotrexate, nicotine replacement therapy, phenobarbitone, phenytoin, quinine, sodium valproate, testosterone
What is Category X with regard to medicine use in pregnancy? What are two examples?
Category X - drugs which have such a high risk of causing permanent damage to the fetus that they should not be used in pregnancy or when there is a possibility of pregnancy.
e.g. misoprostol, thalidomide
Define polypharmacy. Why might it be a problem?
- polypharmacy is the use of five or more drugs including prescribed, over-the-counter and complementary medicines
- increased risk of adverse reactions and drug interactions
A women asks you about whether it is safe to take non-steroidal antiinflammatories like aspirin, ibuprofen and diclofenac in pregnancy, what would you say?
- recommended to avoid NSAIDs in pregnancy, particularly after 30 weeks as they can be harmful to fetus
- vital to consult a doctor or pharmacist
A women asks you about whether it is safe to take non-steroidal decongestants such as pseudoephedrine and phenylephrine in pregnancy, what would you say?
- it is recommended to avoid oral decongestants such as pseudoephedrine and phenylephrine in pregnancy
- a decongestant nasal spray containing oxymetazoline or xylometzoline may be used for 3-5 days
- steam inhalation or sodium chloride nasal sprays may also provide relief
A women says she has been constipated and is wondering what is safe to take in pregnancy?
- increased dietary fibre
- plenty of water
- consult doctor or pharmacist - can recommend a stool softener or osmotic laxative such as lactulose that are generally safe if taken as recommended in pregnancy.
A women says she has been getting heartburn and is wondering what is safe to take in pregnancy?
- small regular meals
- avoid rich or spicy meals, chocolate, citrus, coffee
- avoid lying down straight after eating
- talk to doctor or pharmacist about recommended antacids
A women has vaginal thrush and is wondering what is safe to take in pregnancy?
- very common in pregnancy
- topical antifungal creams and pessaries containing clotrimazole, miconazole and nystatin are considered safe
- oral fluconazole is often not recommended unless advised by doctor
- see doctor for further advice
What is a positive way to present information about the risk of fetal malformations and drug risk in pregnancy?
“in every pregnancy; there is a 97-99% chance that a woman will give birth to a child who does not have a major birth defect. [insert applicable drug name] has/have not been shown to change that”
What is the trade name of paracetamol and codeine (30mg)?
Panadeine Forte
What is the usual indication for Panadeine forte?
moderate to severe pain
What is the mode of action of Panadeine forte?
Paracetamol has analgesic and antipyretic effects, thought to inhibit prostaglandin synthesis and block pain impulse generation, acts on the hypothalamus to regulate temperature
Codeine is an opiod analgesic, metabolised to morphine, binds to opiod receptor and alters perceptions to an emotional response to pain
What is the stock strength, usual dose and max dose of Panadeine Forte?
Paracetamol 500mg and Codeine 30mg per tablet
2 tabs PO Q4H
maximum dose 4g paracetamol in 24 hours
What are adverse reactions/precautions are important to remember when considering Panadeine Forte?
- dependence
- constipation (fluids/stool softener)
- nausea
- sedation and reduced alertness
- urticaria
- urinary retention
- excessive use can cause irreversible liver damage
What is the trade name of oxytocin?
Syntocinon
What are the three main indications for oxytocin?
- induction/augmentation of labour
- active managment of third stage
- treatment of PPH
What is the mode of action of oxytocin?
Oxytocin is a uterotonic, it stimulates smooth muscle of uterus producing rhythmic contractions, particularly towards term when receptors are more sensitive.
What is the stock strength and usual dose of oxytocin?
- 10IU/ml ampule and 5IU/ml ampule
- dosage depends on indication and local protocol
- IOL or augmentation: usually 10IU/1000ml saline IV infusion commence at 12ml/min and increase 30 minutely
- 3rd stage: usually 10IU/ml IM or IV given after birth
- PPH: normal 3rd stage management then 40IU/1000ml saline 0.9% IV infusion at 250ml/hr if placenta is out.
What are adverse reactions/precautions are important to remember for oxytocin?
- painful contractions
- nausea and vomiting
- headache
- flushing
- water intoxication
- hypotension
- fetal distress
- disseminated intravascular coagulation
- regular monitoring of P, BP, RR, contraction pattern, fetal wellbeing as applicable
- need resting tone of at least 90 seconds
What are important considerations when prescribing drugs to brestfeeding women?
- appropriate treatment for mother
- safety of drug and likelihood of side effects for mother and baby
- is it licensed for paediatric use?
- availability of data
- age and maturity of the baby (particularly renal and hepatic)
- frequency of breastfeeding
- volume of breastmilk being consumed
- whether the mother wants to cease breastfeeding
- any sensitivity of the infant to the drug
- infants health (prematurity, respiratory depression, heart failure, renal disease)
- therapeutic range
- duration of treatment
- therapeutic range
What factors influence drug transfer to milk?
- poorly understood
- time after birth (gap junctions closing until day 3)
- plasma protein binding (only free drug can diffuse, higher less transfer)
- drug half-life (shorter considered safer as less accumulation)
- molecular size
- lipid solubility
