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1 Choosing Choosing Choosing Choosing an Appropriate an Appropriate an Appropriate an Appropriate Oral Contraceptive for Oral Contraceptive for Oral Contraceptive for Oral Contraceptive for Your Your Your Your Patient Patient Patient Patient DANIEL MAJERCZYK, PHARM.D. ASSISTANT PROFESSOR OF CLINICAL SCIENCES ROOSEVELT UNIVERSITY, COLLEGE OF PHARMACY 1400 N. ROOSEVELT BLVD. | SCHAUMBURG, IL 60173 Conflicts of Interest: Dr. Majerczyk declares no conflicts of interest, real or apparent, and no financial interests in any company, product, or service mentioned in this program, including grants, employment, gifts, stock holdings, and honoraria. Objectives: Pharmacist: 1. Describe the mechanism of action, types, benefits, and risks of oral contraceptives. 2. Identify risks and contraindications to oral contraceptives. 3. Choose the best and most effective contraceptive for a patient. 4. Discuss possible side effect/s associated with the use of oral contraceptives. 5. List patient counseling points on side effects and missed dose instructions for oral contraceptives. Pharmacy Technician: 1. Discuss the types of drug classes found in oral contraceptives. 2. Recognize common adverse effects of oral contraceptives. 3. Identify patient characteristics that may be contraindications to the use of oral contraceptives. Question 1 The progestin component of the contraceptive pill works by: A. Inhibiting the release of follicle stimulating hormone (FSH) from the anterior pituitary B. Increasing bleeding C. Thinning the cervical mucus D. Thickening the cervical mucus thicker, making it harder for the sperm to penetrate

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Choosing Choosing Choosing Choosing an Appropriate an Appropriate an Appropriate an Appropriate Oral Contraceptive for Oral Contraceptive for Oral Contraceptive for Oral Contraceptive for Your Your Your Your PatientPatientPatientPatientDANIEL MA JERCZYK, PHARM.D.ASSISTANT PROFESSOR OF CLINICAL SCIENCESROOSEVELT UNIVERSITY, COLLEGE OF PHARMACY1400 N. ROOSEVELT BLVD. | SCHAUMBURG, IL 60173

Conflicts of Interest:

Dr. Majerczyk declares no conflicts of interest, real or apparent, and no financial interests in any company, product, or service mentioned in this program, including grants, employment, gifts, stock holdings, and honoraria.

Objectives: Pharmacist:

1. Describe the mechanism of action, types, benefits, and risks of oral contraceptives.

2. Identify risks and contraindications to oral contraceptives.

3. Choose the best and most effective contraceptive for a patient.

4. Discuss possible side effect/s associated with the use of oral contraceptives.

5. List patient counseling points on side effects and missed dose instructions for oral contraceptives.

Pharmacy Technician:

1. Discuss the types of drug classes found in oral contraceptives.

2. Recognize common adverse effects of oral contraceptives.

3. Identify patient characteristics that may be contraindications to the use of oral contraceptives.

Question 1

The progestin component of the contraceptive pill works by:

A. Inhibiting the release of follicle stimulating hormone (FSH) from the anterior pituitary

B. Increasing bleeding

C. Thinning the cervical mucus

D. Thickening the cervical mucus thicker, making it harder for the sperm to penetrate

2

Question 2

A contraindication to initiating a combined hormonal contraceptive is:

A. A migraine without aura and age <35 years old

B. Smoking 2 packs per day and age <35 years old

C. Current chlamydial infection

D. Blood pressure of 162/90 mmHg

Question 3

Which of the following is one of the most effective forms of contraception available:

A. The implant

B. The patch

C. The pill

D. The condom

Question 4

All of the following are considered potential unwanted side effects associated with the use of

hormonal contraceptives except:

A. Nausea

B. Dermatological Improvement

C. Weight gain

D. Hirsutism

Question 5

L.R. takes her norethindrone 0.35 mg pill every day at 3 pm. She was delayed today and realized

it it now 7 pm. What action should the patient take now:

A. She should take the pill ASAP

B. She must take 2 pills at once

C. She must use back-up contraception for the next 48 hours

D. She should start a new pack tomorrow

3

Background1,2

US has one of the highest rates of unintended pregnancy in the developed country

~ 50% of all pregnancies are unintended

~ 40% end in abortion

~ 1/3 of American women have an abortion at some point in their lives

Abortion rates has declined recently, the gap between the lower rates of unintended pregnancy in wealthy people and higher rates in disadvantaged groups has widened over the past 2 decades

This disparity suggests there is limited access to contraception for some women and adolescents, and points to the importance of addressing birth control with all patients at risk for unintended pregnancy

Meet K.L. & Y.D.

K.L.

◦ 27 year old female

◦ Current smoker

◦ Has seasonal allergies and thyroid disease

Y.D.

◦ 30 year old female

◦ Has a very busy life

◦ Afraid of needles

◦ Takes Rx and OTC medications

Questions to consider:

1. What more would you like to know/ask?

2. What contraceptive would you choose and why?

Initial Counseling3

Contraceptive counseling should aim to maximize:

◦ Efficacy

◦ Patient satisfaction

◦ Long-term adherence

Selecting an appropriate contraceptive method requires:

◦ Complete medical history, with special focus on ruling out the most common contraindications

◦ The World Health Organization (WHO) has produced a chart recording the absolute and relative contraindications to the different contraceptive methods

Medical Eligibility for Initiating Contraception: Absolute and Relative Contraindications4

http://www.reproductiveaccess.org/wp-content/uploads/2014/12/chart.pdf

4

Medical Eligibility for Initiating Contraception: Absolute and Relative Contraindications4

http://www.reproductiveaccess.org/wp-content/uploads/2014/12/chart.pdf

Hormonal Contraceptive Products

Pharmacology

◦ Mechanism of Action (MOA)

◦ Description of how hormonal contraceptive products affect phases of the menstrual cycle

Key features of agents

◦ Progestin content and effect

◦ Estrogen content and effect

◦ Combined (progestin and estrogen)

The Menstrual Cycle5

http://www.onlinebiologynotes.com/ovarian-cycle-menstrual-cycle/

Mechanism of Action (MOA)

Progesterone

◦ Thickens the cervical mucus

◦ Making it harder for the sperm to penetrate

◦ Decreases the likelihood of implantation

◦ Inhibit an estrogen-induced LH surge at mid cycle from the anterior pituitary

Estrogen

◦ Inhibits the release of FSH and LH from the anterior pituitary

◦ Stabilizes the endometrial lining

◦ Decreases breakthrough bleeding

5

Contraception Forms and their Efficacy5

https://www.cdc.gov/reproductivehealth/contraception/unintendedpregnancy/pdf/Contraceptive_methods_508.pdf

Hormonal Contraceptives

More Effective Methods Include:

Pills:

◦ Progestin only

◦ Combination (estrogen and progestin)

Least Effective Methods Include:

◦ Spermicides

◦ Condoms

◦ Withdrawal Method

Progestin Only Contraceptives

Prevent ovulation by inhibiting the release of LH and the LH surge from the pituitary

Also act on the female reproductive system in additional ways:

◦ Thicken cervical mucus

◦ Inhibit sperm penetration past the cervix, into the uterus, and fallopian tubes

◦ Inhibit implantation

◦ By promoting atrophy (thinning) of the endometrial lining

http://e.hormone.tulane.edu/lear

ning/progestins.html

Classification of Progestins6

https://www.medscape.org/viewarticle/559116_6

6

Combination Estrogen/Progesterone

In the combined hormonal contraceptive (CHC) products, estrogens have a secondary role:

Estrogens; usually ethinyl estradiol:

◦ Stabilize the endometrial lining

◦ This minimizes breakthrough bleeding

◦ Help to promote cycle control

http://menopausehealthmatters.

com/progesterone-

deficiency/estrogen-dominance/

Available Monophasic CHC Regimens

Estrogen Progestin

Ethinyl estradiol 20 mcgLevonorgestrel 0.1 mg

Norethindrone acetate 1 mg

Ethinyl estradiol 25 mcg Norethindrone acetate 0.8 mg

Ethinyl estradiol 30 mcg

Levonorgestrel 0.15 mg

Norgestrel 0.3 mg

Norethindrone acetate 1.5 mg

Desogestrel 0.15 mg

Drospirenone 3 mg

Ethinyl estradiol 35 mcg

Ethynodiol diacetate 1 mg

Norgestimate 0.25 mg

Norethindrone 0.4 mg

Norethindrone 0.5 mg

Norethindrone 1 mg

Ethinyl estradiol 50 mcg

Norethindrone 1 mg

Norgestrel 0.5 mg

Ethynodiol diacetate 1 mg

Mestranol 50 mcg Norethindrone 1 mg

Available Multiphasic CHC Regimens

Estrogen Progestin

Ethinyl estradiol 10 to 20 mcg Desogestrel 0.15 mg

Ethinyl estradiol 35 mcg Norethindrone acetate 0.5 to 1 mg

Norgestimate 0.18 to 0.25 mg

Ethinyl estradiol 20 to 35 mcg Norethindrone acetate 1 mg

Ethinyl estradiol 25 mcg Norgestimate 0.18 to 0.25 mg

Desogestrel 0.1 to 0.15 mg

Ethinyl estradiol 30 to 40 mcg Levonorgestrel 0.05 to 0.125 mg

Estradiol valerate 1 to 3 mg Dienogest 2 to 3 mg

Available Extended- and Continuous-Cycle CHC Regimens

Estrogen Progestin

Ethinyl Estradiol 10 mcg x 26 days Norethindrone acetate 1 mg x 24 days

Ethinyl Estradiol 20 mcg x 24 days Norethindrone acetate 1 mg x 24 days

Drospirenone 3 mg x 24 days

Ethinyl Estradiol 20 mcg x 84 days, then 10 mcg x 7 days Levonorgestrel 0.1 mg x 84 days

Ethinyl Estradiol 30 mcg x 84 days Levonorgestrel 0.15 mg x 84 days

Ethinyl Estradiol 30 mcg x 84 days, then 10 mcg x 7 days Levonorgestrel 0.1 mg x 84 days

Ethinyl Estradiol 20 mcg x 42 days, 25 mcg x 21 days, 30 mcg x 21 days, then 10

mcg x 7 days

Levonorgestrel 0.1 mg x 84 days

Ethinyl Estradiol 20 mcg all days, no break Levonorgestrel 90 mcg all days

7

CHC Products

Combination hormonal contraceptives include:◦ Oral formulation

◦ 1 tab po qd

◦ Transdermal formulation ◦ Apply 1 patch qwk x3wk, off x1wk

◦ Vaginal ring◦ 1 ring PV x3wk, off x1wk

CHCs are the most commonly used form of contraception

There are several different progestins used in combination with estrogen in hormonal contraceptives, and these progestins in combination hormonal contraceptive pills differ in the pharmacological effects

◦ These effects can manifest in some women as unwanted side effects◦ Acne and unwanted hair growth – levonorgestrel

Different Forms of Progestin in CHC Pills7

http://www.fainamd.com/resources/Which+OCP+is+Best+Handout.pdf

Progestin Estrogen Androgen

Desogestrel ++++ 0 +++

Levonorgestrel ++++ 0 ++++

Norgestrel +++ 0 +++

drospirenone ++ 0 0

Ethynodiol Acetate ++ +++ +

Norgestimate ++ 0 ++

Norethindrone ++ ++ ++

Norethindrone acetate ++ ++ ++

Dienogest + 0 0

Progestin Only Contraceptives

Progestin Only Pills (POPs) - ”Mini-Pill”

◦ Must be taken at the same time each day

◦ If you miss a pill for more than 3 hours

◦ Must use back-up contraception for the next 48 hours

Injectable

◦ IM and SC

◦ 3 months of contraception

Implant

◦ Long acting and reversible

◦ 3 years of contraception

◦ Office visit for implantation and removal

IUD

◦ Long acting and reversible

◦ Levonorgestrel

◦ Up to 5 years of contraception depending on the device

◦ Office visit for placement and removal

Progestin Only Pills - POPs

https://www.webmd.com/drugs/2/drug-75915/jolivette-oral/details, https://www.goodrx.com/errin/images, http://contracts.digitaltreasure.co.bw/fr-ca/generique-100-mg-avana-prix-le-moins-cher.php,

https://dailymed.nlm.nih.gov/dailymed/archives/fdaDrugInfo.cfm?archiveid=15386, https://www.aegisshield.com/products/janssen/ortho-micronor-035mg-tablet

https://www.goodrx.com/norethindrone/images

8

Non-Contraceptive Benefits of Hormonal Contraceptives

Medicating the symptoms of dysmenorrhea

◦ Painful/difficult menses

Reducing the frequency and length of the menstrual cycle

Reducing menorrhagia

◦ Heavy menstrual bleeding

Reducing the rates of some cancers

◦ Ovarian

◦ Endometrial

Improving certain skin conditions

◦ Acne

Knowledge Check

In the following table, which contraceptive progestin products may offer more of an improvement in dermatologic symptoms?

A. Drospirenone

B. Levonorgestrel

C. Norgestrel

D. Desogestrel

Re-Cap

Contraceptives prevent pregnancy through a variety of mechanisms

All hormonal contraceptives prevent pregnancy by preventing ovulation through inhibition of the hypothalamic-pituitary-gonadal axis

◦ The variety of hormonal contraceptives available today provide women with many options for an individualized approach to preventing pregnancy and providing benefits beyond the prevention of pregnancy

Pharmacist’s Role in Assessing Women for Hormonal Contraception

Provide access to prescription and OTC products

Advise patients about:

◦ Appropriate selection and use of contraceptive products

◦ What to do in the event of misses pills, or delayed start

◦ Provide counseling when there is a potential of drug interactions or when side effects are reported

9

Hormonal Contraception Self-Screening Tool Questions8

http://www.pharmacy.ca.gov/laws_regs/1746_1_pt.pdf

Pharmacy Practitioners Patient Care Process9

https://jcpp.net/patient-care-process/

Hormonal Contraceptive Indications

All Contraceptives All Contraceptives

Prevent pregnancy

Additional Benefits of Some Contraceptives Additional Benefits of Some Contraceptives

Dermatological Improvement

Treat symptoms of premenstrual dysphoric disorder (PMDD)

Menstrual Suppression

Off-label Uses Off-label Uses

Regulation of menstrual cycle

Risk reduction for certain cancers

PCOS management

Reduction of menstrual bleeding

Contraceptive Method Selection

SafetySafety EfficacyEfficacyPast

experiencePast

experienceEase of accessEase of access

ReversibilityReversibility ConvenienceConvenience AdherenceAdherencePersonal

preference Personal

preference

Cost Cost Privacy Privacy

10

Guidelines for Providing Hormonal Contraception5

https://www.cdc.gov/reproductivehealth/contraception/pdf/summary-chart-us-medical-eligibility-criteria_508tagged.pdf

Guidelines for Providing Hormonal Contraception5

11. https://www.cdc.gov/reproductivehealth/contraception/pdf/summary-chart-us-medical-eligibility-criteria_508tagged.pdf

How to Interpret the MEC

How to Interpret the MEC

Use the method

Do not use the method

11

Guidelines for Providing Hormonal Contraception5

http://apps.who.int/iris/bitstream/10665/252267/1/9789241565400-eng.pdf

Contraception App By Centers For Disease Control and Prevention

https://itunes.apple.com/us/app/contraception/id595752188?mt=8

Assessment Procedure for Prescribing Hormonal Contraceptives

Selected Practice Recommendations for Examination and Tests Needed5

http://apps.who.int/iris/bitstream/10665/252267/1/9789241565400-eng.pdf

12

Assessing Blood Pressure5

http://apps.who.int/iris/bitstream/10665/252267/1/9789241565400-eng.pdf

What to Consider When Selecting and Initiating a Hormonal Contraceptive Regimen

MethodMethod

Evaluate how the method is used

Ease of use may influence adherence

•Higher failure rates are

associated with

complicated instructions

EfficacyEfficacy

How effective is the method in preventing

pregnancy?

Perfect use of pills show <1% failure rate

Typical use of pills show a ~9% failure

rate

BleedingBleeding

Combined pills, patches, rings = Expect regular

monthly bleeding

Extended cycle regimen = Less

frequent bleeding

Progestin only methods =

Amenorrhea (no bleeding)

ReversibilityReversibility

Can a method be reversed and how

quickly?

AccessAccess

How will the woman be able to access the

method?

Patient Case 1 – Meet K.L.

27 year old female

Smokes 5 - 6 cigarettes per day

Medications: Levothyroxine, Celebrex, and Claritin

LMP began 2 weeks ago

No sexual intercourse since then

Has taken a pill in the past – but does not remember the name

Indicates that she would prefer an oral pill at this time

Patient Case 1 – Meet K.L.

13

Patient Case 1 – Meet K.L.

Patient Case 2 – Meet Y.D. 30 year old female

Wants to switch from the pill to a method that is administered less frequently

She does not like needles and does not have time for frequent office appointments

Has a sulfa allergy

Medications: St. John’s Wort, ProAir Inhaler, Advair Discus , Ibuprofen and drospirenone/ethinyl estradiol 3 mg/30 mcg

Does not smoke

Today is the 1st day of her menstrual cycle

Is interested in a patch or a ring

So, which contraceptive would be safe and effective for Y.D.?

Patient Case 2 – Meet Y.D.

Patient Case 2 – Meet Y.D.

14

Patient Case 2 – Meet Y.D.

MethodMethod

Depot Injection

IUD

Progestin Implant

Patch

Ring

Safe to UseSafe to Use

Yes

Yes

Yes

Yes

Yes

Meet Patient

Preference

Meet Patient

Preference

No

No

No

Yes

Yes

Y.D. expressed a desire to try a patch or a ring

https://www.webmd.com/drugs/2/drug-166145/xulane-transdermal/details

https://www.goodrx.com/nuvaring/images

Side Effects Associated with Hormonal Components of CHCs

Too Much Estrogen

Too Much Estrogen

Nausea

Breast tenderness

Increased blood

pressure/headache

Melasma

Too Little EstrogenToo Little Estrogen

Early to mid-cycle

breakthrough

bleeding

Increased spotting

Hypomenorrhea

Too Much Progestin Too Much Progestin

Breast tenderness

Headache

Fatigue

Changes in mood

Too Little ProgestinToo Little Progestin

Late breakthrough

bleeding

Too Much AndrogenToo Much Androgen

Increased

appetite/weigh gain

Oily skin/acne

Hirsutism

Dyslipidemia

Side Effect/s Management

Too Much Estrogen

Too Much Estrogen

Woman on pills with high estrogen doses may complain of headaches or breast tenderness

•Switching to a CHC with a lower

estrogen dose may be beneficial

•Generally, no changes should be

typically made within the 1st 3 cycles

as the woman adjusts to the medication

Too Little EstrogenToo Little Estrogen

Woman experiencing breakthrough bleeding early in the cycle may

require a pill with a higher dosage of estrogen

Other possible causes of breakthrough bleeding include:

•Drug interactions with tobacco or

CYP 450 enzyme inducers

•Non adherence to medication

Too Much AndrogenToo Much Androgen

These symptoms are usually weight gain, acne,

or dyslipidemia

These woman may better tolerate a product containing a less

androgenic progestin or one containing Drospirenone

How to Manage Late/Missed Doses of a Combined Oral Contraceptive10

If 1 hormonal pill is late: (<24 hours since a pill should have been taken)If 1 hormonal pill is late: (<24 hours since a pill should have been taken)

If 1 hormonal pill has been missed: (24 to <48 hours since a pill should have been taken)If 1 hormonal pill has been missed: (24 to <48 hours since a pill should have been taken)

• Take the late or missed pill ASAP

• Continue taking the remaining pills at the usual time (even if it means taking 2 pills on the same day)

• No additional contraceptive protection is needed

• Emergency contraception is usually NOT needed but may be considered if the hormonal pills were missed earlier in the cycle or in the last week of the pervious cycle

15

How to Manage Late/Missed Doses of a Combined Oral Contraceptive10

If ≥2 consecutive hormonal pills have been missed: (≥48 hours since a pill should have been taken)If ≥2 consecutive hormonal pills have been missed: (≥48 hours since a pill should have been taken)

•Take the most recent pill ASAP (any other missed pills should be discarded)

•Continue taking the remaining pills at the usual time (even if it means taking 2 pills on the same day)

•Use back-up contraception (e.g., condoms) or avoid sexual intercourse until hormonal pills have been taken for 7 consecutive days

If pills were missed in the last week of the hormonal pills (e.g., days 15 – 21 for 28-day pill packs):If pills were missed in the last week of the hormonal pills (e.g., days 15 – 21 for 28-day pill packs):

•OMIT the hormone-free interval by finishing the hormonal pills in the current pack and starting a NEW pack the next day

•If unable to start a new pack immediately, use back-up contraception (e.g., condoms) or avoid sexual intercourse until hormonal pills from a new pack have been taken for 7 consecutive days

Emergency contraception SHOULD be considered if hormonal pills were missed during the 1st week and unprotected sexual intercourse occurred in the previous 5 daysEmergency contraception SHOULD be considered if hormonal pills were missed during the 1st week and unprotected sexual intercourse occurred in the previous 5 days

Serious Side Effects

Thrombogenicdisorders

Thrombogenicdisorders

Heart attackHeart attack

StrokeStroke DVT/PEDVT/PEAge

Smoking

HTN

Immobility

Obesity

Pill, Patch & Ring Warning Signs - ACHES

ABDOMINAL PAIN

ABDOMINAL PAIN

Blood clot in the pelvis or liver

[mesenteric or pelvic vein

thrombosis]

Blood clot in the pelvis or liver

[mesenteric or pelvic vein

thrombosis]

VomitingVomiting

CrampingCramping

WeaknessWeakness

CHEST PAINCHEST PAIN

Blood clot in the lung or heart

vessels [pulmonary embolism

or myocardial infarction]

Blood clot in the lung or heart

vessels [pulmonary embolism

or myocardial infarction]

Heart attack, anginaHeart attack, angina

Chest or heart pain, left arm

and shoulder pain

Chest or heart pain, left arm

and shoulder pain

Coughing and shortness of

breath

Coughing and shortness of

breath

HEADACHESHEADACHES

StrokeStroke

Blurred vision, spots, zigzag

lines, weakness, difficulty

speaking

Blurred vision, spots, zigzag

lines, weakness, difficulty

speaking

Sudden intellectual

impairment

Sudden intellectual

impairment

EYE PROBLEMS

EYE PROBLEMS

Stroke or retinal vein

thrombosis

Stroke or retinal vein

thrombosis

Complete or partial loss of

vision

Complete or partial loss of

vision

SEVERE LEG PAIN

SEVERE LEG PAIN

Inflammation and blood clots

of a leg in the leg

Inflammation and blood clots

of a leg in the leg

Swelling, heat or redness,

tenderness in leg

Swelling, heat or redness,

tenderness in leg

Re-Cap

We have assessed whether a woman is an appropriate candidate for a hormonal contraceptive

Described the features of the currently available forms of hormonal contraceptives

Determined if a woman meets the eligibility criteria for specific methods of hormonal contraception

16

Questions/Contact Info:

Daniel Majerczyk, Pharm.D.Assistant Professor of Clinical SciencesRoosevelt University, College of Pharmacy1400 N. Roosevelt Blvd. | Schaumburg, IL 60173

Email: [email protected]

References: 1. Hatcher R. Contraceptive technology. 20th ed. New York: Ardent Media; 2011.

2. Finer LB, Henshaw SK. Disparities in rates of unintended pregnancy in the United States, 1994 and 2001; Perspect Sex Reprod Health. 2006,38:90-96.

3. World Health Organization. Medical eligibility criteria for contraceptive use. 5th ed. 2015. http://www.who.int (last accessed 12 November 2017).

4. Reproductiveaccess. Reproductiveaccess Online Web Site. Available at: https://www.reproductiveaccess.org/resource/medical-eligibility-initiating-contraception/. Accessed November 12, 2017.

5. World Health Organization. Medical eligibility criteria for contraceptive use. 5th ed. 2015. http://www.who.int (last accessed 12 November 2017).

6. Stewart FH, Harper CC, Ellertson CE, et al. Clinical breast and pelvic examination requirements for hormonal contraception: Current practice vs evidence. JAMA. 2001;285:2232-2239.

7. Centers for Disease Control and Prevention (CDC). Update to CDC's US medical eligibility criteria for contraceptive use, 2010: revised recommendations for the use of hormonal contraception among women at high risk for HIV infection or infected with HIV. MMWR Morb Mortal Wkly Rep. 2012;61:449-452.

8. Landry DJ, Wei J, Frost JJ. Public and private providers' involvement in improving their patients' contraceptive use. Contraception. 2008;78:42-51.

9. Cipolle RJ, Strand LM, Morley PC. Pharmaceutical Care Practice: The Patient Centered Approach to Medication Management, 3rd ed. New York: McGraw-Hill; 2012.

10. White KO, Westhoff C. The effect of pack supply on oral contraceptive pill continuation: a randomized controlled trial. Obstet Gynecol. 2011;118:615-622.