PHENYTOIN LEVEL CHECK

Q. A 72-year-old man with known epilepsy and hypertension is admitted with pneumonia. His drug history includes aspirin, phenytoin, bendroflumethiazide and amlodipine. His heart rate is 67, blood pressure 170/93, sats 96 per cent on 2 L of oxygen. Neurological examination is normal. His doctor requests blood tests
including phenytoin level. What is the correct indication for this test?
A. Routine check
B. Ensure levels are not toxic
C. Confirm patient compliance
D. Ensure therapeutic level reached
E. Reassure the patient

Ans:  C

Explanation: 

 Routine measurement of phenytoin levels (A) is not good practice, they should be ordered with a question in mind. They can be helpful either for adjustment of phenytoin dose or looking for toxicity or patient compliance. Phenytoin levels are useful when adjusting the dose to avoid toxicity as phenytoin has zero-order kinetics (once elimination reaches saturation rates, it cannot be cleared any faster so a small change in the dose may result in high blood levels), but there is no reason to change this patient’s dose. There is no reason to suspect phenytoin toxicity either (B) as there are no signs or symptoms such as nystagmus, diplopia, dizziness, ataxia, confusion. However, his high blood pressure may be caused by noncompliance with his medication (C). Although target levels exist (D), they are imprecise and not applicable to all patients. Seizures may be well controlled with low levels, thus phenytoin should be adjusted according to the clinical picture and not levels. Levels are not helpful in reassuring the patient in this situation (E), although they often inappropriately reassure the doctor who requests them.

ANKYLOSING SPONDYLITIS

Q. A 22 year old man has had an acute, painful, red right eye with blurring of vision for one day. He had a similar episode one year ago and has had episodic back pain and stiffness relieved by exercise and diclofenac for four years. What is the most likely cause of his red eye?
a) Chorioretinitis
b) Conjunctivitis
c) Episcleritis
d) Iritis
e) Keratitis

Ans: d) Iritis


Explanation: 

Ankylosing spondylitis (AS):  is a chronic inflammatory disease of the spine and sacroiliac joints, of unknown aetiology. 
Prevalence: 0.25–1%. 

 Men present earlier:  M:F≈ 6:1 at 16yrs old, and ~2:1 at 30yrs old. ~90% are HLA B27 +ve
 
Symptoms and signs: The typical patient is a man <30yrs old with gradual onset of low back pain, worse at night, with spinal morning stiff ness relieved by exercise. Pain radiates from sacroiliac joints to hips/buttocks, and usually improves towards the end of the day. There is progressive loss of spinal movement (all directions)—hence thoracic expansion. . The disease course is variable; a few progress to kyphosis, neck hyperextension, and spino-cranial ankylosis. Other features include enthesitis , especially Achilles tendonitis, plantar fasciitis, at the tibial and ischial tuberosities, and at the iliac crests. Anterior mechanical chest pain due to costochondritis and fatigue may feature. 
 Acute iritis occurs in~⅓ of patients and may lead to blindness if untreated (but may also have occurred many years before, so enquire directly). AS is also associated with osteoporosis (up
to 60%), aortic valve incompetence (<3%) and pulmonary apical fibrosis. 

Tests: Diagnosis is clinical, supported by imaging (MRI is most sensitive and better at detecting early disease). Sacroiliitis is the earliest X-ray feature, but may appear late: look for irregularities, erosions, or sclerosis aff ecting the lower half of the sacroiliac joints, especially the iliac side. Vertebral syndesmophytes are characteristic: bony proliferations due to enthesitis between ligaments and vertebrae. These fuse with the vertebral body above, causing ankylosis. In later stages, calcification of ligaments with ankylosis lead to a ‘bamboo spine’ appearance.
Also: FBC (normocytic anaemia), increased ESR, CRP, HLA B27+ve (not diagnostic).
 
Management:  Exercise, not rest, for backache, including intense exercise regimens to maintain posture and mobility—ideally with a physiotherapist specializing in AS. NSAIDS  usually relieve symptoms within 48h, and they may slow radiographic progression. 41 TNF alfa blockers etanercept, adalimumab and golimumab are indicated in severe active AS if NSAIDS fail . Local
steroid injections provide temporary relief. Surgery includes hip replacement to improve pain and mobility if the hips are involved, and rarely spinal osteotomy. There is increased risk of osteoporotic spinal fractures (consider bisphosphonates). Prognosis: There is not always a clear relationship between the activity of arthritis and severity of underlying infl ammation (as for all the spondyloarthritides). Prognosis is worse if ESR >30; onset <16yrs; early hip involvement or poor response to NSAIDS.



Source: Oxford Book Of Clinical Medicne 

CHEMOTHERAPY SKIN REACTION

Q. A 57-year-old man with metastatic adenocarcinoma of the lung is attending for cycle three of his palliative pemetrexed/cisplatin chemotherapy. During his cisplatin infusion, he noticed his arm becoming painful, swollen and red at the cannula site. The most likely cause of this is:

A. Cellulitis

B. Venous thrombosis

C. Extravasation of chemotherapy

D. Adverse drug reaction

E. Normal chemotherapy reaction

Ans: C

 Extravasation of chemotherapy (C) is describing the inadvertent administration of drugs into the surrounding tissues rather than into a vein. This may be caused by a displaced cannula. Depending on the agent being administered, the degree of injury may range from a mild skin reaction to skin necrosis and thus, it requires urgent attention. The chemotherapy infusion should be stopped, the arm elevated and the affected area marked. A senior doctor should be informed and the guidelines on extravasation for that particular agent should be checked. Cisplatin is classified as an exfoliant, which can cause inflammation and shedding of the skin. A cold pack should be applied and advice of a plastic surgeon sought. Saline washout of the extravasation site may be necessary in this case. Acute onset of cellulitis (A) after administration of chemotherapy is an unlikely answer. Cancer patients are at higher risk of venous thrombosis (B) and all patients attending hospital should have a venous thromboembolism risk assessment and prescription of a low-molecular weight heparin if required.

In this situation though, it is more likely that extravasation has caused the pain and swelling, particularly in light of the skin reaction. Since this is his third cycle of chemotherapy, an adverse drug reaction (D) is unlikely. You are not expected to know the details of managing extravasation of chemotherapy. However, it is important to know that such a reaction after administration of chemotherapy is not normal (E) and senior attention should be sought.

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