Obstetrics, gynaecology and UTI case studies: Case study level 1 – Primary Dysmenorrhoea

Learning outcomes
Level 1 case study: You will be able to:

1. describe the risk factors
2. describe the disease
3. describe the pharmacology of the drug
4. outline the formulation including drug molecule, excipients, etc. for the medicines
5. summarise basic social pharmacy issues (e.g. opening containers, large labels).

Scenario

Fifteen-year-old Miss SM comes to your pharmacy accompanied by her mother with a prescription for mefenamic acid 500 mg t.d.s. (three times a day) p.r.n. (when necessary). Supply 42 tablets. You recognise the mother as she has recently been in to purchase over-the counter ibuprofen for her daughter.

Questions

1. What is primary dysmenorrhoea?

2. What are the risk factors for developing primary dysmenorrhoea?

3a. What group of drugs does mefenamic acid belong to?

3b. How does mefenamic acid work in the treatment of primary dysmenorrhoea?

3c. What are the side-effects of mefenamic acid tablets (see BNF)?

4a. Which non-drug treatments are advocated in primary dysmenorrhoea?

4b. What else could the GP prescribe if mefenamic acid did not adequately control the symptoms of primary dysmenorrhoea?

5. What counselling must be given as you know the mother has previously purchased ibuprofen OTC?

6. What other formulations of mefenamic acid are there?

Answers

1       What is primary dysmenorrhoea?

Dysmenorrhoea is cyclical, lower abdominal or pelvic pain which may also radiate to the back and thighs, occurring before or during menstruation or both. Primary dysmenorrhoea occurs in the absence of any obvious underlying disease that may be cause of pain.

2        What are the risk factors for developing primary dysmenorrhoea?

Risk factors include:

• nulliparity
• obesity
• cigarette smoking
• being sexually inactive
• late child-bearing
• positive family history.

3a        What group of drugs does mefenamic acid belong to?

Mefenamic acid is a non-steroidal anti-inflammatory drug (NSAID). It exhibits anti-inflammatory, analgesic and antipyretic activities. The mechanism of action is not completely understood but may be related to prostaglandin synthetase inhibition.

3b        How does mefenamic acid work in the treatment of primary dysmenorrhoea?

Elevated prostaglandin levels are present in the endometrial fluid of dysmenorrhoeic women and correlate well with the degree of pain. NSAIDs are inhibitors of prostaglandin synthesis and probably work by decreasing uterine prostaglandin levels and uterine contractility.

3c       What are the side-effects of mefenamic acid tablets (see BNF)?

Diarrhoea or rashes (withdraw treatment), vomiting, flatulence, constipation, ulcerative stomatitis. Less commonly paraesethesia and fatigue. Rarely, thrombocytopenia, haemolytic anaemia and aplastic anaemia are reported. Convulsions in overdosage..

4a      Which non-drug treatments are advocated in primary dysmenorrhoea?

High-frequency transcutaneous electrical nerve stimulation (TENS) is an option 158 Pharmacy Case Studies for women who prefer not to take medication. TENS seems to work by altering the body’s ability to receive or perceive pain signals, rather than having a direct effect on the uterine contractions.

4b      What else could the GP prescribe if mefenamic acid did not adequately control the symptoms of primary dysmenorrhoea?

Combined oral contraceptives (COCs) are helpful, especially when prostaglandin inhibition fails. COCs are thought to relieve dysmenorrhoea by inducing endometrial thinning and inhibiting ovulation, resulting in low levels of uterine prostaglandins.

5       What counselling must be given as you know the mother has previously purchased ibuprofen OTC?

You have been prescribed with mefenamic acid 500-mg tablets. Take one tablet three times a day while having period pain. Some women find that it helps to start taking these painkillers a day or so before the period is expected to start. Alternatively, start to take them at the onset of pain or bleeding, whichever happens first. Take them regularly while the pain lasts. Mefenamic acid is a drug in the same group of drugs as ibuprofen; it is important that both mefenamic acid and ibuprofen are not taken together as this will increase side-effects in the stomach.

6       What other formulations of mefenamic acid are there?

If mefenamic acid tablets are too big for Miss SM to swallow then a branded capsule formulation (Ponstan) is available. The GP would need to be contacted to agree the change for Drug Tariff reimbursement purposes.